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Studies to Investigate the Pharmacokinetic Interactions Between Ranolazine and Ketoconazole, Diltiazem, or Simvastatin During Combined Administration in Healthy Subjects

From CV Therapeutics Inc, Palo Alto, California (Dr Jerling, B.-L. Huan, Dr Leung, N. Chu, Dr Abdallah), and Medeval Ltd, Manchester, United Kingdom (Dr Hussein).

Address for reprints: Markus Jerling, MD, PhD, CV Therapeutics Inc, 3172 Porter Drive, Palo Alto, CA 94304.

	ABSTRACT

TOP ABSTRACT METHODS RESULTS DISCUSSION CONCLUSIONS ACKNOWLEDGEMENTS REFERENCES

 
The interactions of ranolazine, a new antianginal compound, with inhibitors and substrates of the CYP3A isoenzyme family were studied in 1 open-label and 4 double-blind, randomized, multiple-dose studies. In healthy adult volunteers, the authors sought (1) to determine the steady-state pharmacokinetics, safety, and tolerability of immediate- and sustained-release ranolazine with and without ketoconazole, diltiazem, or simvastatin and (2) to evaluate the effect of ranolazine on the pharmacokinetics of diltiazem, simvastatin, simvastatin metabolites, and HMG-CoA reductase activity. Ketoconazole increased ranolazine plasma concentrations and reduced the CYP3A4-mediated metabolic transformation of ranolazine, confirming that CYP3A4 is the primary metabolic pathway for ranolazine. Diltiazem reduced oral clearance of ranolazine in a dose-dependent manner. Simvastatin did not affect ranolazine pharmacokinetics, although ranolazine increased the AUC and C_max of simvastatin, simvastatin acid, 2 simvastatin metabolites, and HMG-CoA reductase activity by <2-fold. Administration of ranolazine in combination with diltiazem or simvastatin was safe and well tolerated during the interval studied.

Key Words: Ranolazine • ketoconazole • diltiazem • simvastatin • drug interactions

Ranolazine is almost completely metabolized, with <5% of the administered dose excreted unchanged.³ Metabolism of ranolazine is complex, with cytochrome P450 (CYP) 3A-mediated pathways accounting for the majority of ranolazine biotransformation. CYP2D6 accounts for less than 20% of ranolazine metabolism.⁴ Previous studies in human volunteers documented 4 predominant metabolites: CVT-2514 (present, on average, at 33% of parent compound levels at steady state), CVT-2738 (27%), CVT-4786 (21%), and CVT-2512 (12%). Studies with human liver microsomes indicate that CVT-2738 and CVT-4786 (a further metabolite of CVT-2534, which is a primary metabolite of ranolazine) are formed primarily via the CYP3A pathways; CVT-2514 is primarily catalyzed by CYP2D6; and CVT-2512 is formed by CYP3A and CYP2D6. The following metabolites that exceed 1% of ranolazine exposure have also been measured and characterized: CVT-2537, CVT-2513, CVT-2535, CVT-3248, CVT-3388/CVT-5028, CVT-2551, and CVT-5030 (Figure 1).

View larger version (28K): [in this window] [in a new window]   Figure 1. Ranolazine metabolic pathways.

The CYP3A isoenzymes are involved in the metabolism of many drugs. CYP3A enzymes are found primarily in the liver and small bowel and are extensively involved in first-pass metabolism.⁵ Because ranolazine is metabolized by CYP3A, concomitant administration with other CYP3A substrates can increase the ranolazine plasma concentration and affect ranolazine pharmacokinetic parameters.

Ketoconazole, an antimycotic, is one of the most potent inhibitors of CYP3A isoenzymes and therefore has clinically significant drug interactions with other CYP3A substrates. It has become standard practice to use ketoconazole to achieve maximum inhibition when determining the significance of CYP3A interactions. Ketoconazole is a competitive reversible CYP3A inhibitor that significantly decreases the in vivo clearance of cyclosporine,⁶ terfenadine,⁷ benzodiazepines,^8,9 and several other compounds. Diltiazem, a calcium channel blocker commonly used for the treatment of hypertension and angina, is a moderate CYP3A inhibitor,¹⁰ with clinically significant drug interactions documented with nifedipine, cyclosporine A, midazolam, triazolam, and lovastatin.¹¹ Simvastatin weakly inhibits CYP3A but is extensively metabolized by the CYP3A isoenzyme; its clearance is reduced by concomitant administration with itraconazole,¹² diltiazem,^13,14 erythromycin,¹⁵ verapamil,¹⁵ and grapefruit juice.¹⁶ Because simvastatin is administered as a prodrug, it is of value to measure both HMG-CoA reductase activity and the presence of metabolites known to inhibit HMG-CoA reductase activity as evidence of a drug interaction.¹⁷

In these studies, we sought to compare the pharmacokinetics of multiple oral doses of ranolazine sustained release (SR) administered alone and following coadministration of ketoconazole, diltiazem, or simvastatin under steady-state conditions of both drugs. Interactions between diltiazem and ranolazine immediate release (IR) were also assessed. A secondary objective was to further assess the safety and tolerability of multiple oral doses of ranolazine administered alone and following coadministration of ketoconazole, diltiazem, and simvastatin under steady-state conditions of both drugs.

	METHODS

TOP ABSTRACT METHODS RESULTS DISCUSSION CONCLUSIONS ACKNOWLEDGEMENTS REFERENCES

 
Study Design
Study A was a double-blind, randomized, multipledose, parallel-group study in healthy male and female subjects aged 18 to 45 years, with the primary objective to compare the pharmacokinetics of multiple oral doses of ranolazine alone and following ketoconazole administration. The study was subdivided in 2 consecutive parts, including different subjects in which 6 subjects received ranolazine placebo and 15 active ranolazine in each part. In the first part, ranolazine/placebo SR 375 mg was administered twice daily for 5 days, followed by ranolazine/placebo SR 375 mg twice daily, coadministered with ketoconazole 200 mg twice daily for 4 days, and a single morning dose of both ranolazine/placebo SR 375 mg and ketoconazole 200 mg on day 10. The second part had a similar design but with a ranolazine/placebo dose of 1000 mg twice daily. Pharmacokinetic profiles were collected on days 5 and 10 at steady state for ranolazine in the absence and presence of ketoconazole, respectively. Steady-state conditions for ranolazine were ensured from the assessment of trough concentrations collected on all study days.

Study B was an open-label, multiple-dose comparison of the pharmacokinetics of simvastatin given with and without ranolazine. The study also compared the pharmacokinetics of ranolazine given with and without simvastatin. Seventeen healthy volunteers received a single dose of simvastatin 80 mg; the pharmacokinetic profiles of simvastatin and its metabolites were characterized, and HMG-CoA reductase inhibitor activity was measured on day 1. Ranolazine SR was then initiated with an initial dose of 1750 mg, followed by 1000 mg bid for a total of 7 days (days 3-9), with the addition of simvastatin 80 mg daily during the last 4 days of dosing (days 6-9). Pharmacokinetic profiles were determined for ranolazine on days 5 and 9. Profiles were determined for simvastatin and its metabolites, as well as HMG-CoA reductase inhibitor activity, on days 6 and 9. It was ensured from consecutive trough levels that all profiles on days 5 and 9 reflected steady-state conditions. Liver function tests were performed on day 1, before dosing, and on days 6 and 11. Tests included alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma glutamyl transpeptidase (GGT), and total bilirubin. Creatinine phosphokinase (CPK) was also followed.

Study C was a double-blind, randomized, placebo-controlled, 4-way crossover study in 12 healthy males aged 18 to 45 years, with the primary objectives to evaluate the effect of diltiazem on ranolazine instant-release pharmacokinetic parameters, as well as the effect of ranolazine instant release on diltiazem pharmacokinetic parameters. Subjects received either diltiazem 60 mg tid or placebo for 7 days. From days 4 to 7, ranolazine IR 240 mg tid or placebo was added. The 4 different combinations at day 7 were diltiazem/ranolazine, diltiazem/placebo, placebo/ranolazine, and placebo/placebo. Pharmacokinetic profiles for both diltiazem and ranolazine were collected on days 4 and 7 with separate comparisons of pharmacokinetic parameters on days 4 and 7.

Study D had a design similar to that of study C but was conducted with ranolazine SR at a dose of 500 mg bid and had a dosing duration of 8 days. Fourteen subjects were included, and 12 completed the study.

Study E was a double-blind, placebo-controlled, parallel-group study with the primary objective to determine the effect of diltiazem modified release (MR) on ranolazine SR pharmacokinetics. Cohorts of 8 healthy males received either placebo or active diltiazem MR once daily (180, 240, or 360 mg) for 8 days. Ranolazine SR 1000 mg bid was added from days 4 to 8. Ranolazine pharmacokinetic profiles were collected over 12 hours on day 4 after the first ranolazine dose and on day 8 after the last dose of both compounds.

Each study was approved and monitored by an independent ethics committee.^* Subjects in all studies gave written informed consent and were in good health, as determined from medical history, physical examination, and routine laboratory studies. Subjects were excluded if they had a history of clinically significant illness, were currently taking medications, had a history of drug or ethanol abuse, or tested positive for human immunodeficiency virus. In studies A and B, subjects were not allowed to consume caffeine or grapefruit juice immediately before or during the study. In studies A, B, and C, subjects were not allowed to use tobacco immediately before or during the study. Patients enrolled in study E had to be nonsmokers. Subjects in all 5 studies were advised to avoid alcohol during the study period. In study A, women of childbearing potential must have been using adequate contraceptive precautions and have had a negative pregnancy test at study entry.

Study Drug
In study B, ranolazine SR and simvastatin were supplied as tablets. In studies A and D, ranolazine SR and placebo were supplied as tablets that were identical in appearance and dispensed in identical packaging to maintain blinding. In study C, ranolazine IR and placebo were supplied in identical capsules. Placebo tablets or capsules were formulated with the same excipients as ranolazine SR or IR tablets or capsules. Subjects in study E received open-label ranolazine SR tablets. Ketoconazole tablets were supplied as Nizoral 200-mg tablets (Janssen-Cilag, Saunderton, United Kingdom). In studies C and D, diltiazem was supplied as Tildiem 60 tablets (Lorex Pharmaceuticals, Maidenhead, United Kingdom) and repackaged into capsules that were identical in appearance to placebo. In study E, diltiazem MR (Cardizem CD tablet, Aventis Pharmaceuticals, Kansas City, Mo) was repackaged in capsules identical in appearance to placebo to maintain blinding.

Safety Assessments
Safety assessments were similar between studies and included medical history, physical examination, electrocardiogram (ECG), and laboratory assessments (hematology, blood chemistry, and urinalysis) at screening. During the study period and at study completion, the following were assessed in each study on a predetermined schedule: vital signs, ECG, laboratory variables, urinalysis, and the occurrence of any adverse events. Adverse events were defined as any unfavorable or unintended sign, symptom, or disease associated with use of the study drug, whether or not it was considered related to the study drug. Adverse events were collected throughout the study period and during the period of study follow-up. In study A, ECG abnormalities were managed as needed by repeat ECG, continued monitoring, medical intervention, or cessation of dosing as necessary. Subjects in study A had plasma ranolazine determinations monitored at the study site to ensure that the concentration did not exceed 10 000 ng/mL in any subject at any time during the study.

Analytical Methods
Study A. Concentrations of ranolazine and metabolites in plasma were determined by tandem mass spectrometric assays following high-performance liquid chromatography separation (LC/MS/MS). For the analysis of ranolazine, CVT-2514, CVT-2512, and CVT-2738, plasma samples were precipitated with acetonitrile and methanol containing deuterated (D₃)-ranolazine as an internal standard (IS). Following centrifugation, an aliquot of the supernatant was diluted with water containing 0.1% formic acid, and the pH was adjusted to 3.0 with concentrated ammonium hydroxide. High-performance liquid chromatography (HPLC) was performed on a Phenomenex Synergi Hydro-R column (2 x 50 mm) using a Waters Alliance 2795 delivery system (Milford, Mass). The mobile phase consisted of water containing 0.1% formic acid, with pH adjusted to 3.0 with ammonium hydroxide and acetonitrile containing 0.1% formic acid. Chromatography was carried out using the following gradient program: 0 to 1 minutes of 16% acetonitrile, pumped at 0.2 mL/min; 1 to 5.5 minutes of linear gradient to 28% acetonitrile at 0.5 mL/min; and 5.5 to 5.9 minutes of 28% acetonitrile at 0.5 mL/min. The effluent was directed into a Micromass Quattro Ultima mass spectrometer (Beverly, Mass). Selective detection was performed in multiple-reaction monitoring (MRM) and positive ionization modes by monitoring the transition of m/z 428.3 278.9, 431.3 281.9, 414.5 265.3, 322.1 142.9, and 248.3 99.1, corresponding to the protonated molecular ion and most abundant fragment of ranolazine, D₃-ranolazine, CVT-2514, CVT-2512, and CVT-2738, respectively. The quantification limit of the method was 50 ng/mL for ranolazine and 10 ng/mL for CVT-2514, CVT-2512, and CVT-2738, using a maximum volume of 0.1 mL of heparinized plasma.

For CVT-3388, CVT-2551, CVT-5050, CVT-2513, CVT-2535, CVT-3248, CVT-2537, and CVT-4786, HPLC was performed on a Phenomenex Mercury MS Luna C-18 column cartridge (2 x 20 mm) with a Phenomenex SecurityGuard C-18 guard cartridge (2 x 4 mm) using a Shimadzu LC system (Pleasanton, Calif) equipped with a Leap Model HTS PAL autosampler (Carrboro, NC). The mobile phase consisted of water containing 0.03% formic acid, with pH adjusted to 5.0 with ammonium hydroxide and acetonitrile. The gradient program used was 0 to 0.6 minutes of 5% acetonitrile, pumped at 0.333 mL/min; 0.6 to 2.6 minutes of linear gradient to 50% acetonitrile; 2.61 to 2.90 minutes of 90% acetonitrile; 2.91 to 3.20 minutes of 5% acetonitrile at 0.5 mL/min; and 3.21 to 3.70 minutes of 5% acetonitrile at 0.333 mL/min. The effluent was directed into a Sciex API 3000 triple quadrupole mass spectrometer (Applied Biosystem/MDS, Foster City, Calif). Selective detection was performed in MRM and positive ionization modes by monitoring the transition of m/z 444.4 279.1, 444.4 263.1, 444.4 295.0, 266.2 98.9, 180.1 98.9, 264.4 99.1, 394.3 280.3, and 262.2 113.1, corresponding to the protonated molecular ion and most abundant fragment of CVT-3388, CVT-2551, CVT-5050, CVT-2513, CVT-2535, CVT-3248, CVT-3930 (IS), and CVT-6650 (IS), respectively. CVT-4786, CVT-2537, and phenyllactic acid (IS) were detected in negative ionization mode by monitoring the transition of m/z 180.1 98.9, 211.0 122.5, and 165.0 102.7, respectively. The limit of quantitation was 50 ng/mL for CVT-4768 and 10 ng/mL for the rest of 7 metabolites using a maximum volume of 0.1 mL plasma.

Study B. Simvastatin lactone and its metabolites, 3'-hydroxy simvastatin lactone, 6'-exomethylene simvastatin lactone, and simvastatin acid were quantified using an assay based on liquid/liquid extraction and HPLC/electrospray mass spectrometry analysis. Standard and quality control samples were prepared using serum that was withdrawn from healthy volunteers not on medication with either prescription or over-the-counter drugs. For quantification, mevastatin lactone provided by Sigma Chemical Co (St. Louis, Mo) was used as the internal standard for the lactone compounds. Mevastatin acid was used as the internal standard for simvastatin acid.

To each serum sample, saturated sodium chloride was added. The samples were then vortexed before the internal standard solution was added. Sample aliquots were transferred to HPLC inserts, and water was added to increase stability.

Simvastatin lactone, 3'-hydroxy simvastatin lactone, and 6'-exomethylene simvastatin lactone were analyzed by a positive signal method. Simvastatin acid was run using a different method for negative signals.

For simvastatin lactone and its metabolites, 3'-hydroxy simvastatin lactone, and 6'-exomethylene simvastatin lactone, the extracted sample was injected onto the LC/MS/MS system. Samples were kept at +4°C in the temperature-controlled autosampler. Samples of simvastatin lactone, 3'-hydroxy simvastatin lactone, and 6'-exomethylene simvastatin lactone were loaded onto a 4 x 20-mm C8 extraction column, filled with Hypersil MOS of 5 µm particle size, and were washed using a mobile phase consisting of 2 mM ammonium acetate (pH 4.0) (adjusted with acetic acid solution)/acetonitrile (8:2). After 1 minute, the switching valve was activated, and the compounds were eluted in the backflush mode from the extraction column onto a 100 x 2.1-mm analytical column filled with Symmetry C18 material of 3.5 µm particle size. After 5.8 minutes, the switching valve was activated again, and the extraction column was cleaned with acetonitrile/water 9/1 v/v (gradient from 0-4 mL, 1 minute, then 2 mL, 3.8 minutes) and reequilibrated to the starting conditions.

The mobile phase of the analytical column consisted of 2 mM ammonium acetate (pH 4.0) and methanol. For the first 7 minutes, the mobile phase was 26% of 2 mM ammonium acetate (pH 4). For the following 1 minute, the column was washed with 95% acetonitrile and was reequilibrated to the starting conditions for 1.5 minutes. The flow was 0.5 mL/min and the column temperature 40°C. The total runtime was 9.8 minutes. For simvastatin lactone, 3'-hydroxy simvastatin lactone, 6'-exomethylene simvastatin lactone, and mevastatin lactone, we used the positive mode. Single ions were recorded. Under the conditions used, the sodium adducts gave the strongest signals. The mass spectrometer was focused on m/z = 441.2 (simvastatin lactone), 439 (6'-exomethylene simvastatin lactone), 457 (3'-hydroxy simvastatin lactone), and 413 (mevastatin lactone, internal standard), with a dwell time of 294 ms.

For simvastatin acid, 50 µL of the extracted sample was injected onto the LC/LC/MS system. Samples were kept at +4°C in the temperature-controlled autosampler. Samples of simvastatin acid were loaded onto a20 x 4-mm C8 extraction column, filled with Hypersil MOS of 5 µm particle size, and were washed using a mobile phase consisting of 2 mM ammonium acetate (pH 4.0) (adjusted with acetic acid solution)/acetonitrile (8:2). The flow was 5 mL/min. After 1 minute, the switching valve was activated, and the compounds were eluted in the backflush mode from the extraction column onto a 100 x 2.1-mm analytical column filled with Symmetry C18 material of 3.5 µm particle size. After 4.8 minutes, the switching valve was activated again, and the extraction column was cleaned with acetonitrile/water 9/1 v/v (gradient from 0-4 mL, 1 minute, then 2 mL, 1.8 minutes) and reequilibrated to the starting conditions.

The mobile phase of the analytical column consisted of 2 mM ammonium acetate (pH 4.0) and methanol. For the first 5 minutes, the mobile phase was 19% of 2 mM ammonium acetate (pH 4.0). For the following 1 minute, the column was washed with 95% acetonitrile and was reequilibrated to the starting conditions for 1.8 minutes. The flow was 0.5 mL/min and the column temperature 40°C. The total runtime was 6.8 minutes. Single ions were recorded. In the negative mode for simvastatin acid and mevastatin acid, we focused on the hydrogen adducts that gave the strongest signals. The mass spectrometer was focused on m/z = 435.7 (simvastatin acid) and 406 (mevastatin acid, internal standard), with a dwell time of 589 ms.

HMG-CoA reductase inhibition activity. Simvastatin was isolated from human plasma by protein precipitation using acetonitrile/acetone. The supernatant was evaporated to dryness under nitrogen and reconstituted with distilled water. The reconstituted mixture was incubated with buffer solution containing ¹⁴C-HMG-CoA, cofactors, and HMG-CoA reductase from human liver microsomes (provided by Merck & Company, Rahway, NJ). The ¹⁴C-mevalonate was separated from the substrate after lactonization to [¹⁴C]-mevalonolactone by HCl on a small ion-exchange column (AG 1-8X). The effluent from the column containing the product was collected directly into scintillation vials and counted. The [¹⁴C]-mevalonolactone, measured in cpm, was used to construct a standard curve using a point to point, linear versus log.

Studies C and D. Plasma levels of ranolazine were measured by reversed-phase HPLC using fluorometric detection following solid-phase extraction, a similar procedure as described under study E. Plasma levels of diltiazem were determined by reversed-phase HPLC using ultraviolet detection following solvent extraction.¹⁸ Control samples were analyzed daily during routine use of the HPLC method. These samples spiking ranolazine or diltiazem into plasma from untreated subjects were stored frozen before analysis.

Study E. Plasma levels of ranolazine and CVT-2514 were measured by reversed-phase HPLC using fluorometric detection. Aliquots of plasma were fortified with RS-87986-193 (IS) and vortexed for 30 seconds. All samples were then transferred to an automatic extractor (a Tecan Genesis RSP10) and were extracted using an automatic method. A 96-well Bond-Elut block (C18, 100 mg) was conditioned using methanol, followed by distilled water and finally 0.05 M sodium hydroxide. Aliquots of plasma samples were passed through the Bond-Elut block followed by distilled water and methanol/water. Ranolazine and the IS were then eluted from the columns by methanol. Following evaporation under nitrogen at 50°C, samples were reconstituted in mobile phase and transferred to autosampler vials. An aliquot was injected onto the HPLC system for analysis. High-performance liquid chromatography was performed on a Hypersil ODS 5 µ column C-18 column (size: 4.6 x 100 mm) using a PerkinElmer Binary 250 LC system equipped with a Gilson 232XL autosampler. The mobile phase consisted of methanol:0.01 M KH₂PO4:acetonitrile 45:40:15 (v/v/v) pumped at 1 mL/min isocratically for 13 minutes. The effluent from the column was directed into a fluorescence detector (Shimadzu, RF551) with excitation and emission wavelength set at 274 and 310 nm, respectively. The limit of quantitation was 10 and 8.5 ng/mL for ranolazine and CVT-2514, respectively.

Pharmacokinetic Analysis
Study A. The steady-state plasma concentration-time profiles of ranolazine, CVT-2512, CVT-2514, CVT-2738, CVT-2537, CVT-4786, CVT-2513, CVT-2535, CVT-2551, CVT-5030, CVT-3248, and CVT-3388/CVT-5028 were determined within 12 hours after the morning dose on days 5 and 10 and were analyzed with noncompartmental methods using WinNonlin, Version 3.2. Concentrations below the lower limit of detection were set at zero. The parameters of minimum observed steady-state plasma concentration (C_ss,min), maximum observed steady-state plasma concentration (C_ss,max), and the concentration at 12 hours postdose (C₁₂) were direct observations. The area under the plasma concentration-time profile over 1 dosing interval () (AUC) was calculated by the linear trapezoidal method. The average steady-state plasma concentration (C_avg) was determined by dividing AUC by 12 ().

Study B. The following were calculated for simvastatin and its metabolites in the serum of HMG-CoA reductase inhibitor activity and ranolazine in plasma: C_max, C_ss,min, K_el (the apparent elimination rate constant), AUC_{12 h} (ranolazine) and AUC_{24 h} (simvastatin analytes), and AUC_0- (computed as linear trapezoidal rule T_last + C_Tlast/K_el). Analysis of variance (ANOVA), with factors subject and day, was used for natural log-transformed variables of C_max, AUC_{24 h}, and AUC_0-. Ninety percent confidence intervals (CIs) for the difference in computed parameter least squares means were calculated and expressed as a percentage of the reference.

Studies C and D. Any plasma level that was below the limit of quantitation of ranolazine or diltiazem was defined as 0. The following parameters were determined for ranolazine and diltiazem: C_max, AUC_0- (AUC over the dosing interval using actual sampling times by the trapezoidal rule), and the ratio of ranolazine AUC_0- with and without diltiazem administration.

Study E. The following parameters were determined for ranolazine using a model-independent approach. C_max and C₁₂ (concentration 12 hours postdose) were determined from plasma concentration-time profiles. AUC_0-12 and AUC_0-24 were estimated by the linear trapezoidal rule. AUC_0- was calculated by AUC_0-24 + C/ß, where C is the plasma concentration at 24 hours, and ß is the terminal elimination rate constant estimated using log-linear regression during the terminal phase, using at least 3 time points. Estimation of pharmacokinetic parameters in plasma was performed by using WinNonlin Professional, Version 1.5.

Statistical Methods
In all studies, descriptive statistics were used to summarize safety data (including vital signs, laboratory data, and ECG). Adverse events were summarized by severity and relationship to study drug. Adverse events were coded by COSTART and displayed by frequency and body system.

Study A. The logarithmically transformed pharmacokinetic parameters (C_ss,max and AUC) of ranolazine and its metabolites in the presence and absence of ketoconazole on days 5 and 10 were compared statistically using ANOVA. Ninety percent CIs were calculated for treatment differences in the logs of the parameters, then back-transformed to obtain 90% CIs for the ratios. Absence of an interaction was to be concluded when the 90% CI for the ratio fell entirely within 80% to 125%.

Study B. For simvastatin and related compounds, the primary comparison was based on logarithmically transformed values for AUC_0- after the first dose on day 1, as well as AUC_0-24 on day 9 at steady state. Point estimates and 90% CIs for the difference of the parameters between days 9 and 1 were computed. For ranolazine, the logarithmically transformed pharmacokinetic parameters AUC_0-12 and C_max were analyzed using ANOVA models. Point estimates and 90% CIs for the difference of the parameters between days 9 and 5 were computed from the ANOVA.

Studies C and D. All pharmacokinetic data were analyzed by mixed-effects ANOVA models. Days 4 and 7 in study C and days 4 and 8 in study D were analyzed separately. Pharmacokinetic variables were analyzed on both untransformed and logarithmically transformed data. Following ANOVA, all comparisons at individual time points were performed by 2-sided t tests; significance was at P < .05.

Study E. ANOVA was used to test for differences between each dose of diltiazem MR plus ranolazine SR (test) versus placebo plus ranolazine SR (reference) on days 4 and 8. A 90% CI difference between the test and reference treatments was calculated from the ANOVA model. This result was used to test for drug interaction by computing the 90% CI for the ratio of test/reference for C_max, C₁₂, AUC_0-12, and AUC_0-. Lack of drug interaction was concluded if the 90% CI was between 80% and 120% for untransformed C_max, C₁₂, AUC_0-12, and AUC_0- or between 80% and 125% for logarithmically transformed C_max, C₁₂, AUC_0-12, and AUC_0-. All calculations were performed using SAS Version 6.12 for UNIX.

	RESULTS

TOP ABSTRACT METHODS RESULTS DISCUSSION CONCLUSIONS ACKNOWLEDGEMENTS REFERENCES

 
Study Subjects
Baseline characteristics and reasons for withdrawals for the enrolled subjects are shown in Table I.

Pharmacokinetic Analysis
Study A. Mean pharmacokinetic values following twice-daily oral administration of ranolazine SR 375 or 1000 mg, with and without concomitant administration of ketoconazole 200 mg twice daily, are shown in Table II. Following coadministration of 200 mg ketoconazole, mean C_ss,min, C_ss,max, C₁₂, and C_ss,avg all increased by between 2.5- and 4.5-fold. Ranolazine elimination half-lives after the last dose on day 10 in the presence of ketoconazole were of a similar magnitude for the 375-mg bid and 1000-mg bid doses. Ranolazine half-lives could not be accurately determined on day 5 due to the dosing interval of 12 hours providing data for less than 2 half-lives. Pharmacokinetic determinations were also conducted for the 11 ranolazine metabolites present at >1% relative to ranolazine: CVT-2512, CVT-2514, CVT-2738, CVT-2537, CVT-4786, CVT-2513, CVT-2535, CVT-2551, CVT-5030, CVT-3248, and CVT-3388/CVT-5028. Values for AUC_0-12 at steady state are depicted in Table III. The metabolic ratio decreased by 5.6-fold for CVT-2512, 2.1-fold for CVT-2514, 4.6-fold for CVT-2738, and 6.1-fold for CVT-4786, indicating the relative dependencies on CYP3A. For the other metabolites, a decrease in metabolic ratio to a varying degree was observed. The resulting absolute plasma concentration increased for CVT-2514, CVT-2551, and CVT-5030; decreased for CVT-4786; and remained essentially unchanged for CVT-2512 and CVT-2738 and the other more minor metabolites.

Study B. Simvastatin had no significant effect on ranolazine pharmacokinetics. The 90% CIs for the ratio of mean AUC_0-12, C_max, and C_min at days 5 and 9 were all within 80% to 125% (data not shown). In contrast, ranolazine affected simvastatin pharmacokinetic parameters (Table IV). In the presence of ranolazine SR, C_max increased about 2-fold for simvastatin lactone and simvastatin acid and slightly <2-fold for the HMG-CoA reductase inhibitor activity. The corresponding AUC increases were in the range of 40% to 60%. The increase was less pronounced for 6'-exomethylene-simvastatin lactone; a decrease was observed for 3'-hydroxy-simvastatin lactone.

Study C. Ranolazine IR had no effect on diltiazem pharmacokinetic parameters at day 4 or 7. However, at ranolazine steady state on day 7, diltiazem 60 mg 3 times daily increased the ranolazine AUC by 85%, on average, and increased C_max by almost 2-fold and C_min by more than 2-fold (Table V).

Study D. Ranolazine SR had no effect on diltiazem pharmacokinetic parameters at day 4 or 8. At ranolazine steady state on day 8, diltiazem 60 mg 3 times daily caused a statistically significant increase in all ranolazine SR pharmacokinetic parameters (Table VI). The relative increase in ranolazine AUC_0-12 on day 8 was 90%, on average.

Study E. Pharmacokinetic parameters are shown in Table VII for ranolazine SR 1000 mg twice daily in the presence of 3 different doses of diltiazem. AUC_0-12 for ranolazine increased by 52%, 93%, and 139% for increasing doses of diltiazem 180, 240, and 360 mg, respectively. Ranolazine half-lives did not show any consistent trend of changes with increasing doses of diltiazem.

Safety Evaluation
Ranolazine combined with simvastatin or diltiazem was well tolerated, as well as the lower dose of ranolazine (375 mg twice daily) with ketoconazole. At the higher ranolazine dose (1000 mg twice daily), the combination with ketoconazole resulted in intolerable adverse events in some subjects.

Study A. The most commonly reported adverse events were headache and dizziness. In part A, adverse events were comparable between placebo (15 reports) and ranolazine SR 375 mg twice daily (11 reports) and were generally mild in nature. After the addition of ketoconazole, the number of adverse event reports increased significantly in the ranolazine-treated group relative to placebo (39 vs 7 reports, respectively), but most remained mild in severity. In part B, there were significantly more adverse events in the ranolazine-treated group (1000 mg twice daily) than in the placebo group (54 vs 12 reports, respectively) in the absence of ketoconazole and in the presence of ketoconazole (82 vs 16 reports, respectively). A greater proportion of these adverse events was of mild severity. There were more headaches, dizziness, and nausea in the ranolazine SR 1000-mg group than the ranolazine SR 375-mg group.

Study B. There were no clinically significant changes in vital signs, physical examination, ECG, hematology, blood chemistry, or urinalysis. All values for AST and bilirubin were within the normal range. Alanine aminotransferase was slightly above the normal range in 1 subject on day 1, in 2 subjects on day 6, and in 3 subjects on day 11. On day 1, GGT was slightly higher than the normal range in 1 subject, but there were no increased values during the dosing period. Creatinine phosphokinase was slightly higher than the normal range in 1 subject before dosing on day 1, but no subject had increased values during the dosing period. None of the increased values for these parameters was considered to be of clinical significance by the study physicians. Adverse events were infrequent, mild or moderate, and transient. The most common events were headache (n = 5, 28%) or nausea (n = 3, 17%).

Study C. There were no significant effects on hematology, blood chemistry, or urinalysis. There were minor and inconsistent effects on diastolic blood pressure, heart rate, ECG intervals, and cardiac function as assessed by the bioimpedance method. Most changes on the ECG were related to known cardiac electrophysiological effects of diltiazem. There was a statistically significant interaction on day 4 between ranolazine IR and diltiazem on mean systolic blood pressure, -5.7 mm Hg supine and -7.1 mm Hg standing. This corresponded to steady-state levels of diltiazem and peak ranolazine levels after the first ranolazine dose. However, subjects were generally asymptomatic, and this reduction would not likely be clinically significant. This interaction was not observed on day 7 when both diltiazem and ranolazine IR were at steady state. The increase in ranolazine plasma levels after diltiazem coadministration was not associated with an increase in adverse events. Lightheadedness/feeling faint was reported in all groups, generally occurring after the subjects had been fasting and supine.

Study D. There were no significant effects on hematology, blood chemistry, or urinalysis. There were few and inconsistent effects on hemodynamic and ECG data. There was a statistically significant reduction in diastolic blood pressure (8.3 mm Hg, standing) on day 4, 4 hours postdose, when diltiazem/ranolazine SR was compared with diltiazem/placebo. The rise in ranolazine plasma levels following coadministration with diltiazem was not associated with an increase in adverse events; the incidence of adverse events was similar in both groups. Headache was the most frequently reported adverse event (19 reports) and occurred in subjects taking placebo as well as in those taking diltiazem and/or ranolazine.

Study E. The combination of diltiazem MR and ranolazine SR was well tolerated; all adverse events were mild in severity. The most frequently reported event during combination treatment was rash (n = 18), which was attributed to the ECG electrode adhesive in all but 1 subject. Adverse events reported in more than 1 subject during combination treatment included dizziness (ranolazine SR/diltiazem MR, n = 3; ranolazine SR/placebo, n = 2), 1-degree atrioventricular (AV) block, palpitation, rhinitis, asthenia, chest pain, nausea, and euphoria (each n = 2). There were no significant changes in laboratory values, overall ECG parameters, or vital signs.

	DISCUSSION

TOP ABSTRACT METHODS RESULTS DISCUSSION CONCLUSIONS ACKNOWLEDGEMENTS REFERENCES

 
Competition for or inhibition of CYP3A isoenzymes is the underlying mechanism in many significant drug interactions. Documenting these interactions with ranolazine has important implications for dosing with other CYP3A substrates. The results of the study evaluating the coadministration of ketoconazole with ranolazine confirm that CYP3A4 is the primary cytochrome P450 isoenzyme responsible for ranolazine metabolism.^3,4 A contribution of other members of the CYP3A family cannot be excluded. Use of ketoconazole with ranolazine SR 375 or 1000 mg increased parameter estimates for C_ss,min, C_ss,max, C₁₂, C_avg, and AUC. Metabolic ratios for the majority of metabolites decreased in the presence of ketoconazole, consistent with formation primarily through CYP3A. Ranolazine concentrations increased slightly more than proportional to dose from 375 to 1000 mg twice daily, both in the absence and presence of ketoconazole. This has been attributed to a partial saturation of metabolic pathways other than CYP3A and has been observed also in other studies with ranolazine dose escalation.

Diltiazem is a comparatively weaker CYP3A inhibitor compared with ketoconazole.¹⁹ Ranolazine had no effect on diltiazem pharmacokinetic parameters, consistent with in vitro data demonstrating that ranolazine and metabolites are weak inhibitors of CYP3A enzymes. However, concomitant administration with diltiazem resulted in increases in ranolazine exposure in a dose-dependent manner. Ranolazine apparent elimination half-lives did not increase with the diltiazem dose, which is likely explained by the flip-flop kinetics of the SR formulation in which the absorption half-life is longer than the true elimination half-life.

Simvastatin is primarily metabolized by CYP3A isoenzymes. Coadministration with another compound metabolized by CYP3A would potentially increase simvastatin and simvastatin acid concentrations, thereby increasing HMG-CoA reductase inhibitor activity. This would increase the likelihood of adverse events in which the risk of myotoxicity particularly is of high clinical importance.^20,21 Grapefruit juice¹⁵ and itraconazole¹² increase simvastatin AUC by 16-fold and 19-fold, respectively. The effect of ranolazine on simvastatin and simvastatin AUC would not likely be of clinical significance because ranolazine (1000 mg bid) produced increases in simvastatin acid concentrations of less than 2-fold and increases of only 59% (AUC) and 73% (C_max) in HMG-CoA reductase inhibitor activity (Table IV).

At the lower dose, ranolazine SR 375 mg twice daily was generally well tolerated alone or administered concomitantly with ketoconazole. Ranolazine SR 1000 mg twice daily was less well tolerated when coadministered with ketoconazole. Mild to moderate headache and dizziness were the most frequently reported adverse events in the ranolazine SR 1000-mg plus ketoconazole group. The combination of ranolazine and simvastatin was well tolerated, with few transient adverse events reported.

	CONCLUSIONS

TOP ABSTRACT METHODS RESULTS DISCUSSION CONCLUSIONS ACKNOWLEDGEMENTS REFERENCES

 
Ketoconazole increases ranolazine plasma concentrations and reduces the CYP3A-mediated metabolic transformation of ranolazine, confirming the in vitro findings that CYP3A isoenzymes catalyze the primary metabolic pathway for ranolazine. Diltiazem reduces oral clearance of ranolazine in a dose-dependent manner. Ranolazine has minor inhibitory effects on simvastatin metabolism and does not effect diltiazem pharmacokinetic parameters. Administration of ranolazine in combination with diltiazem or simvastatin is safe and well tolerated during the time interval studied.

	ACKNOWLEDGEMENTS

TOP ABSTRACT METHODS RESULTS DISCUSSION CONCLUSIONS ACKNOWLEDGEMENTS REFERENCES

 
Simon Constable and Denise Erkkila are acknowledged for exceptional help with this article. We also thank Hailing Sun and Irving Fong for their contribution in bioanalysis. These studies were supported by CV Therapeutics, Inc (Palo Alto, Calif).

DOI: 10.1177/0091270004273992

^* Inveresk Research Elphinstone Research Centre, Tranent EH33 2NE, Scotland; Covance Clinical Research Unit, Institutional Review Board, Madison, Wisconsin; University of Edinburgh's Special Ethics Committee, University of Edinburgh, Scotland; Western General Hospital, Edinburgh Tayside Committee on Medical Research Ethics, PO Box 75, Vernonholme, Riverside Drive, Dundee DD1 9NL, Scotland.

	REFERENCES

TOP ABSTRACT METHODS RESULTS DISCUSSION CONCLUSIONS ACKNOWLEDGEMENTS REFERENCES

 

1. Pepine CJ, Wolff AA. A controlled trial with a novel anti-ischemic agent, ranolazine, in chronic stable angina pectoris that is responsive to conventional antianginal agents. Ranolazine Study Group. Am J Cardiol. 1999;84: 46-50.[Web of Science][Medline] [Order article via Infotrieve]

2. Zacharowski K, Blackburn B, Thiemermann C. Ranolazine, a partial fatty acid oxidation inhibitor, reduces myocardial infarct size and cardiac troponin T release in the rat. Eur J Pharmacol. 2001;418: 105-110.[CrossRef][Web of Science][Medline] [Order article via Infotrieve]

3. Chu N, Lustig D, Wong S, et al. Disposition of [¹⁴C]-ranolazine in humans [abstract 98]. Drug Metab Rev. 2003;35: 49.

4. Chu N, Soohoo D, Sun H-L, et al. In vitro metabolism of ranolazine [abstract 363]. Drug Metab Rev. 2003;35: 182.

5. Dresser GK, Spence JD, Bailey DG. Pharmacokinetic-pharmacodynamic consequences and clinical relevance of cytochrome P450 3A4 inhibition. Clin Pharmacokinet. 2000;38: 41-57.[CrossRef][Web of Science][Medline] [Order article via Infotrieve]

6. Gomez DY, Wacher VJ, Tomlanovich SJ, Hebert MF, Benet LZ. The effects of ketoconazole on the intestinal metabolism and bioavailability of cyclosporine. Clin Pharmacol Ther. 1995;58: 15-19.[CrossRef][Web of Science][Medline] [Order article via Infotrieve]

7. Honig PK, Wortham DC, Zamani K, Conner DP, Mullin JC, Cantilena LR. Terfenadine-ketoconazole interaction: pharmacokinetic and electrocardiographic consequences. JAMA. 1993;269: 1513-1518.[Abstract/Free Full Text]

8. Olkkola KT, Backman JT, Neuvonen PJ. Midazolam should be avoided in patients receiving the systemic antimycotics ketoconazole or itraconazole. Clin Pharmacol Ther. 1994;55: 481-485.[Web of Science][Medline] [Order article via Infotrieve]

9. von Moltke LL, Greenblatt DJ, Harmatz JS, et al. Triazolam biotransformation by human liver microsomes in vitro: effects of metabolic inhibitors and clinical confirmation of a predicted interaction with ketoconazole. J Pharmacol Exp Ther. 1996;276: 370-379.[Abstract/Free Full Text]

10. Sutton D, Butler AM, Nadin L, Murray M. Role of CYP3A4 in human hepatic diltiazem N-demethylation: inhibition of CYP3A4 activity by oxidized diltiazem metabolites. J Pharmacol Exp Ther. 1997;282: 294-300.[Abstract/Free Full Text]

11. Jones DR, Gorski JC, Hamman MA, Mayhew BS, Rider S, Hall SD. Diltiazem inhibition of cytochrome P-450 3A activity is due to metabolite intermediate complex formation. J Pharmacol Exp Ther. 1999;290: 1116-1125.[Abstract/Free Full Text]

12. Neuvonen PJ, Kantola T, Kivisto KT. Simvastatin but not pravastatin is very susceptible to interaction with the CYP3A4 inhibitor itraconazole. Clin Pharmacol Ther. 1998;63: 332-341.[CrossRef][Web of Science][Medline] [Order article via Infotrieve]

13. Mousa O, Brater DC, Sunblad KJ, Hall SD. The interaction of diltiazem with simvastatin. Clin Pharmacol Ther. 2000;67: 267-274.[CrossRef][Web of Science][Medline] [Order article via Infotrieve]

14. Yeo KR, Yeo WW, Wallis EJ, Ramsay LE. Enhanced cholesterol reduction by simvastatin in diltiazem-treated patients. Br J Clin Pharmacol. 1999;48: 610-615.[CrossRef][Web of Science][Medline] [Order article via Infotrieve]

15. Kantola T, Kivisto KT, Neuvonen PJ. Erythromycin and verapamil considerably increase serum simvastatin and simvastatin acid concentrations. Clin Pharmacol Ther. 1998;64: 177-182.[CrossRef][Web of Science][Medline] [Order article via Infotrieve]

16. Lilja JJ, Kivisto KT, Neuvonen PJ. Grapefruit juice-simvastatin interaction: effect on serum concentrations of simvastatin, simvastatin acid, and HMG-CoA reductase inhibitors. Clin Pharmacol Ther. 1998;64: 477-483.[CrossRef][Web of Science][Medline] [Order article via Infotrieve]

17. Mauro VF. Clinical pharmacokinetics and practical applications of simvastatin. Clin Pharmacokinet. 1993;24: 195-202.[Web of Science][Medline] [Order article via Infotrieve]

18. Zhao H, Chow MS. Analysis of diltiazem and desacetyldiltiazem in plasma using modified high-performance liquid chromatography: improved sensitivity and reproducibility. Pharm Res. 1989;6: 428-430.[CrossRef][Web of Science][Medline] [Order article via Infotrieve]

19. Thummel KE, Wilkinson GR. In vitro and in vivo drug interactions involving human CYP3A. Annu Rev Pharmacol Toxicol. 1998;38: 389-430.[CrossRef][Web of Science][Medline] [Order article via Infotrieve]

20. Ucar M, Mjorndal T, Dahlqvist R. HMG-CoA reductase inhibitors and myotoxicity. Drug Saf. 2000;22: 441-457.[CrossRef][Web of Science][Medline] [Order article via Infotrieve]

21. Gruer PJ, Vega JM, Mercuri MF, Dobrinska MR, Tobert JA. Concomitant use of cytochrome P450 3A4 inhibitors and simvastatin. Am J Cardiol. 1999;84: 811-815.[CrossRef][Web of Science][Medline] [Order article via Infotrieve]
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