Effect of Mild and Moderate Hepatic Impairment (defined by Child Pugh classification and National Cancer Institute-Organ Dysfunction Working Group criteria) on Pexidartinib Pharmacokinetics

Pexidartinib is a novel oral small‐molecule tyrosine kinase inhibitor targeting the colony‐stimulating factor 1 receptor. Pexidartinib undergoes extensive hepatic metabolism via multiple cytochrome P450 and uridine 5'‐diphospho‐glucuronosyl transferase enzymes, with ZAAD‐1006a as the only major metabolite in human plasma. As pexidartinib is extensively metabolized, hepatic impairment (HI) could lead to increased exposure to pexidartinib. The objective of the two phase 1, open‐label studies was to determine the pharmacokinetics of pexidartinib after a single 200‐mg dose in subjects with mild and moderate HI, based on Child–Pugh classification (PL3397‐A‐U123: 8 mild HI and 8 moderate HI vs 16 matched healthy controls) and National Cancer Institute Organ Dysfunction Working Group (NCI‐ODWG) criteria (PL3397‐A‐U129: 8 moderate HI versus 8 matched healthy controls [NCT04223635]). Based on Child–Pugh classification, exposure to pexidartinib (maximum observed concentration [C_max], area under the plasma concentration–time curve up to the last measurable concentration [AUC_last], and extrapolated to infinity [AUC_inf]) was similar in subjects with mild and moderate HI and in respective matched healthy controls, whereas ZAAD‐1006a exposure (AUC) was approximately 27% to 28% and 41% to 48% higher in mild and moderate HI, respectively. According to NCI‐ODWG criteria, total pexidartinib exposure was 42% to 46% higher in subjects with moderate HI, compared with healthy controls, and total ZAAD‐1006a exposure was 70% to 79% higher for subjects with moderate HI, compared with matched healthy controls with normal hepatic function. These findings were used to develop appropriate dose recommendations in patients with hepatic impairment.

Pharmacokinetics and Safety of the Novel Selective Progesterone Receptor Modulator Vilaprisan in Participants With Renal Impairment

This open label, parallel-group study investigated the pharmacokinetics and safety of a single oral 2-mg dose of the novel selective progesterone receptor modulator vilaprisan in participants with impaired renal function compared with age, weight, sex, and race matched controls with normal renal function. Systemic exposure (area under the plasma concentration-time curve [AUC]) and maximum observed concentrations (Cmax ) were compared among 9 participants with moderate renal impairment and matched controls by ANOVA. An additional 4 participants, each with severe renal impairment or normal renal function, contributed to a linear regression analysis exploring any monotone relationship between individual variables and the estimated glomerular filtration rate. The geometric mean AUC was increased by a factor of 1.35 in renally impaired participants compared to normal controls (not statistically significant: least squares mean, 1.346; 90% confidence interval, 0.918-1.973). Cmax was similar in participants with moderate renal impairment and normal renal function (least squares mean, 1.026; 90% confidence interval, 0.779-1.351). Considering the overall variability, there was no correlation between renal function (estimated glomerular filtration rate) and Cmax or AUC of vilaprisan. Single oral administration of vilaprisan 2 mg was well tolerated by all participants, both men and women and irrespective of renal function. The incidence of treatment-emergent adverse events was similar across all groups. Results from this study do not indicate that a dose adjustment will be necessary for vilaprisan when treating patients up to moderate renal impairment.

A Microdose Cocktail to Evaluate Drug Interactions in Patients with Renal Impairment

Renal impairment (RI) is known to influence the pharmacokinetics of nonrenally eliminated drugs, although the mechanism and clinical impact is poorly understood. We assessed the impact of RI and single dose oral rifampin (RIF) on the pharmacokinetics of CYP3A, OATP1B, P-gp, and BCRP substrates using a microdose cocktail and OATP1B endogenous biomarkers. RI alone had no impact on midazolam (MDZ), maximum plasma concentration (C_max ), and area under the curve (AUC), but a progressive increase in AUC with RI severity for dabigatran (DABI), and up to ~2-fold higher AUC for pitavastatin (PTV), rosuvastatin (RSV), and atorvastatin (ATV) for all degrees of RI was observed. RIF did not impact MDZ, had a progressively smaller DABI drug-drug interaction (DDI) with increasing RI severity, a similar 3.1-fold to 4.4-fold increase in PTV and RSV AUC in healthy volunteers and patients with RI, and a diminishing DDI with RI severity from 6.1-fold to 4.7-fold for ATV. Endogenous biomarkers of OATP1B (bilirubin, coproporphyrin I/III, and sulfated bile salts) were generally not impacted by RI, and RIF effects on these biomarkers in RI were comparable or larger than those in healthy volunteers. The lack of a trend with RI severity of PTV and several OATP1B biomarkers, suggests that mechanisms beyond RI directly impacting OATP1B activity could also be considered. The DABI, RSV, and ATV data suggest an impact of RI on intestinal P-gp, and potentially BCRP activity. Therefore, DDI data from healthy volunteers may represent a worst-case scenario for clinically derisking P-gp and BCRP substrates in the setting of RI.

Pharmacokinetics, Safety, and Tolerability of Single-Dose Elbasvir in Participants with Hepatic Impairment

BACKGROUND

The combination of elbasvir and grazoprevir is approved for the treatment of hepatitis C virus genotype 1 or 4 infection.

OBJECTIVE

To evaluate the pharmacokinetics and safety of single-dose elbasvir 50 mg in participants with hepatic impairment.

METHODS

Participants with mild, moderate, or severe hepatic impairment and age-, sex-, and weight-matched healthy controls were enrolled in a 3-part, open-label, sequential-panel, single-dose pharmacokinetic study. Blood samples were collected to assess pharmacokinetics. Safety and tolerability were assessed throughout the study.

RESULTS

Thirty-four participants were enrolled: eight with mild hepatic impairment, 11 with moderate hepatic impairment, seven with severe hepatic impairment, and eight healthy matched controls. Participants with mild, moderate, and severe hepatic impairment demonstrated a numeric, but not statistically significant, decrease in elbasvir exposure compared with controls, with a mean 39, 28, and 12% decrease in area under the concentration-time curve from time 0 extrapolated to infinity, as well as a 42, 31, and 42% decrease in maximum plasma concentration (C _max), respectively. The observed median time to C _max was similar in participants with hepatic impairment and controls. Single-dose administration of elbasvir was well tolerated.

CONCLUSIONS

The pharmacokinetics of elbasvir after a single, oral 50-mg dose were not clinically meaningfully altered in non-HCV-infected participants with mild, moderate, or severe hepatic dysfunction. However, since elbasvir is currently available only as part of a fixed-dose combination with grazoprevir, the fixed-dose combination should not be administered to patients with moderate or severe hepatic impairment, due to the significantly increased plasma grazoprevir exposures in those populations.

The Influence of Hepatic and Renal Impairment on the Pharmacokinetics of a Treatment for Herpes Zoster, Amenamevir (ASP2151): Phase 1, Open-Label, Single-Dose, Parallel-Group Studies

INTRODUCTION

Amenamevir (ASP2151) is a nonnucleoside human herpesvirus helicase-primase inhibitor that was approved in Japan for the treatment of herpes zoster (shingles) in 2017. This article reports the results of two clinical trials that investigated the effects of renal and hepatic impairment on the pharmacokinetics of amenamevir.

METHODS

These studies were phase 1, open-label, single-dose (oral 400 mg), parallel-group studies evaluating the pharmacokinetics, safety, and tolerability of amenamevir in healthy participants and participants with moderate hepatic impairment and mild, moderate, and severe renal impairment.

RESULTS

In the hepatic impairment study, the pharmacokinetic profile of amenamevir in participants with moderate hepatic impairment was generally similar to that of participants with normal hepatic function. In the renal impairment study, the area under the amenamevir concentration versus time curve from the time of dosing up to the time of the last sample with extrapolation to infinity of the terminal phase was increased by 78.1% in participants with severe renal impairment. There was a positive relationship between creatinine clearance and oral and renal clearance for amenamevir in the renal impairment study. In both studies, amenamevir was safe and well tolerated.

CONCLUSION

The findings of the hepatic impairment study indicate that no dosing adjustment is required in patients with moderate hepatic impairment. In the renal impairment study, systemic amenamevir exposure was increased by renal impairment. However, it is unlikely that renal impairment will have a significant effect on the safety of amenamevir given that in previous pharmacokinetic and safety studies in healthy individuals amenamevir was safe and well tolerated after a single dose (5-2400 mg, fasted condition) and repeated doses for 7 days (300 or 600 mg, fed condition), and the amount of amenamevir exposure in the renal impairment study was covered by those studies. These findings suggest that amenamevir does not require dosage reduction in accordance with the creatinine clearance FUNDING: Astellas Pharma.

Moderate Hepatic Impairment Does Not Affect Doravirine Pharmacokinetics

Doravirine is a novel, potent, nonnucleoside reverse-transcriptase inhibitor currently in development for HIV-1 infection treatment. As a substrate for CYP3A-mediated metabolism, doravirine could potentially be affected by liver-function changes. As a portion of the HIV-1-infected population has varying degrees of liver impairment, we investigated the effect of moderate hepatic impairment on the pharmacokinetic profile and tolerability of single-dose doravirine 100 mg in otherwise healthy subjects. A total of 16 subjects aged 44-64 years took part in the open-label, single-dose trial: 8 with moderate hepatic impairment (Child-Pugh score, 7-9; 6 men, 2 women) and 8 healthy individuals (mean age and height matched with the impairment group; 6 men, 2 women). Subjects with hepatic impairment were required to have chronic, stable hepatic impairment with features of cirrhosis of any etiology. Blood sampling revealed that doravirine exposure was similar in both groups. The observed geometric least-squares mean ratio (90% confidence interval; moderately impaired/healthy subjects) was 0.99 (0.72-1.35) for AUC_0-∞ , 0.93 (0.74-1.18) for AUC_0-24 h , 0.90 (0.66-1.24) for C_max , and 0.99 (0.74-1.33) for C_24 h . Geometric mean apparent terminal t½ was ∼18 hours for both groups, whereas median T_max was 2 hours (range, 1-6 hours) and 2.5 hours (range, 1-3 hours) for impaired and healthy individuals, respectively. In addition, doravirine was generally well tolerated. The results demonstrate that moderate hepatic impairment does not have a clinically meaningful effect on doravirine pharmacokinetics. Therefore, dose adjustment should not be necessary in patients with both HIV-1 and moderate hepatic impairment.

Pharmacokinetic Interactions Between Isavuconazole and the Drug Transporter Substrates Atorvastatin, Digoxin, Metformin, and Methotrexate in Healthy Subjects

This article summarizes 4 phase 1 trials that explored interactions between the novel, triazole antifungal isavuconazole and substrates of the drug transporters breast cancer resistance protein (BCRP), multidrug and toxin extrusion protein‐1 (MATE1), organic anion transporters 1/3 (OAT1/OAT3), organic anion‐transporting polypeptide 1B1 (OATP1B1), organic cation transporters 1/2 (OCT1/OCT2), and P‐glycoprotein (P‐gp). Healthy subjects received single doses of atorvastatin (20 mg; OATP1B1 and P‐gp substrate), digoxin (0.5 mg; P‐gp substrate), metformin (850 mg; OCT1, OCT2, and MATE1 substrate), or methotrexate (7.5 mg; BCRP, OAT1, and OAT3 substrate) in the presence and absence of clinical doses of isavuconazole (200 mg 3 times a day for 2 days; 200 mg once daily thereafter). Coadministration with isavuconazole increased mean area under the plasma concentration‐time curves (90% confidence interval) of atorvastatin, digoxin, and metformin to 137% (129, 145), 125% (117, 134),  and 152% (138, 168) and increased mean maximum plasma concentrations to 103% (88, 121), 133% (119, 149), and 123% (109, 140), respectively. Methotrexate parameters were unaffected by isavuconazole. There were no serious adverse events. These findings indicate that isavuconazole is a weak inhibitor of P‐gp, as well as OCT1, OCT2, MATE1, or a combination thereof but not of BCRP, OATP1B1, OAT1, or OAT3.

Evaluation of the single-dose pharmacokinetics of bilastine in subjects with various degrees of renal insufficiency

BACKGROUND

Bilastine is a novel second-generation H1 antihistamine, which has not shown sedative or cardiotoxic effects in clinical trials and in post-marketing experience so far, developed for the symptomatic treatment of allergic rhinoconjunctivitis and urticaria. It has recently been granted marketing authorization for these therapeutic indications in adults and adolescents at a once-daily oral dose of 20 mg in several European countries.

OBJECTIVE

This study was conducted to determine the pharmacokinetics of bilastine at a single oral dose of 20 mg in renally impaired subjects. The need for a dose adjustment in patients with renal insufficiency was assessed by comparing the exposure to bilastine in these subjects with the estimated exposure of a dose corresponding to the safety margin.

METHODS

The study was an open-label, single-dose, parallel-group study of the pharmacokinetics and safety of a single dose of bilastine. The study was conducted as an in-patient setting at a clinical pharmacology facility. A total of 24 male or female subjects aged 18-80 years were to be enrolled in four groups of six subjects each. The groups were as follows: (1) healthy [glomerular filtration rate (GFR) >80 mL/min/1.73 m(2)]; (2) mild renal insufficiency (GFR 50-80 mL/min/1.73 m(2)); (3) moderate renal insufficiency (GFR 30-50 mL/min/1.73 m(2)); and (4) severe renal insufficiency (GFR ≤30 mL/min/1.73 m(2)). A single 20 mg bilastine tablet was administered in a fasted state. Blood and urine samples were collected from pre-dose up to 72 h post-dose for bilastine pharmacokinetic analysis. Pharmacokinetic results were summarized using appropriate descriptive statistics.

RESULTS

There was a clear trend of increasing area under the plasma concentration-time curve (AUC) and maximum plasma concentration (C(max)) through the groups 1-4. The mean AUC from time zero to infinity (AUC(∞)) ranged from 737.4 to 1708.5 ng·h/mL in healthy subjects and severely impaired subjects, respectively. No significant differences among groups in median time to reach Cmax (tmax) or in the mean terminal disposition rate constants for bilastine were found. Renal and plasma clearance paralleled GFR. In all groups of renally impaired subjects the corresponding 90 % confidence interval of both AUC(∞) and AUC from time zero to time of last measurable plasma concentration (AUC(last)) were not within the 0.8-1.25 interval, indicating that bioequivalence between groups could not be demonstrated. The majority of bilastine was excreted within the first 12 h, and elimination was essentially complete by 72 h.

CONCLUSION

An oral dose of bilastine (20 mg) was well-tolerated in renal insufficiency, despite the increase in exposure. The oral plasma clearance to renal clearance ratio [(CL(P)/F)/CL(R)] was approximately equal in the different groups, suggesting that renal excretion was the main elimination route for bilastine, and no alternative elimination routes were used even in severe renal insufficiency. Although exposure to bilastine was higher in renally impaired subjects, it remained well within the safety margins, thus allowing the conclusion that a 20-mg daily dose can be safely administered to subjects with different degrees of renal insufficiency without the need for dose adjustments.

The effect of moderate hepatic impairment on the pharmacokinetics of ipragliflozin, a novel sodium glucose co-transporter 2 (SGLT2) inhibitor

BACKGROUND

Ipragliflozin (ASP1941), a potent selective sodium glucose co-transporter 2 inhibitor, is in development for the treatment of type 2 diabetes mellitus. Ipragliflozin is primarily eliminated via conjugation by the liver as five pharmacologically inactive metabolites (M1, M2, M3, M4 and M6). This study evaluated the effect of moderate hepatic impairment on the pharmacokinetics of ipragliflozin and its metabolites.

METHODS

In an open-label, single-dose, parallel-group study, 16 subjects (eight with moderate hepatic impairment [Child-Pugh score 7-9] and eight healthy, matched controls) received a single oral dose of 100-mg ipragliflozin. Plasma concentrations of ipragliflozin and its metabolites were determined. Adverse events (AEs) and other clinical laboratory parameters were monitored.

RESULTS

All subjects completed the study. Least-squares geometric mean ratios (GMRs) (90 % confidence interval [CI]) for maximum plasma concentration (C max) and area under the plasma concentration-time curve from time zero to infinity (AUC∞) of ipragliflozin were 127 % (93-173 %) and 125 % (94-166 %), respectively, in moderate hepatic impairment versus controls. No changes in elimination half-life and protein binding of ipragliflozin were observed in moderate hepatic impairment subjects. Least-squares GMRs for C max and AUC∞ of M2, the major metabolite, were respectively 95 % (68-133 %) and 100 % (77-130 %) in moderate hepatic impairment versus controls. No deaths, other serious AEs or AEs leading to discontinuation occurred.

CONCLUSIONS

Moderate hepatic impairment had no clinically relevant effects on the single-dose pharmacokinetics of ipragliflozin and its major metabolite, M2. A single oral dose of ipragliflozin, 100 mg, was well tolerated in both healthy subjects and those with moderate hepatic impairment.

Odanacatib, a selective cathepsin K inhibitor to treat osteoporosis: safety, tolerability, pharmacokinetics and pharmacodynamics--results from single oral dose studies in healthy volunteers

AIMS

To evaluate the safety, tolerability, pharmacokinetics and pharmacodynamics of odanacatib (ODN), a cathepsin K inhibitor, in humans.

METHODS

Two double-blind, randomized, placebo-controlled, single oral dose studies were performed with ODN (2-600 mg) in 44 healthy volunteers (36 men and eight postmenopausal women).

RESULTS

Adverse experiences (AEs) with single doses of ODN were transient and mild to moderate, with the exception of one severe AE of gastroenteritis. Headache was the most frequent AE. After absorption of ODN (initial peak concentrations 4-6 h postdose), plasma concentrations exhibited a monophasic decline, with an apparent terminal half-life of ∼40-80 h. The area under the curve0-24 hours (AUC(0-24 h)), concentration at 24 hours (C(24 h)) and maximum concentration (C(max,overal)) increased in a less than dose-proportional manner from 2 to 600 mg. Administration of ODN with a high-fat meal led to ∼100% increases in AUC(0-24 h), C(max,day1), C(max,overall) and C(24 h) relative to the fasted state, while administration with a low-fat meal led to a ∼30% increase in those parameters. Reduction of biomarkers of bone resorption, the C- and N-telopeptides of cross-links of type I collagen, (CTx and NTx, respectively), was noted at 24 h for doses ≥5 mg and at 168 h postdose for ≥10 mg. In postmenopausal women administered 50 mg ODN, reductions in serum CTx of -66% and urine NTx/creatinine (uNTx/Cr) of -51% relative to placebo were observed at 24 h. At 168 h, reductions in serum CTx (-70%) and uNTx/Cr (-78%) were observed relative to baseline. Pharmacokinetic/pharmacodynamic modeling characterized the ODN concentration/uNTx/Cr relation, with a modeled EC50 value of 43.8 nM and ∼80% maximal reduction.

CONCLUSIONS

Odanacatib was well tolerated and has a pharmacokinetic and pharmacodynamic profile suitable for once weekly dosing.

The effect of rifampin on the pharmacokinetics of sirolimus in healthy volunteers

Sirolimus, metabolized primarily by intestinal and hepatic CYP3A4, is a substrate for P-glycoprotein. CYP3A4 inducers would be expected to decrease sirolimus exposure. This open-label, nonrandomized study investigated effects of CYP3A4 induction, by rifampin, on sirolimus pharmacokinetics. Healthy volunteers received sirolimus 20 mg on day 1. After washout period, multiple 600-mg rifampin doses were administered daily for 14 days. On day 9, one 20-mg sirolimus dose was administered after an overnight fast (≥10 hours). Whole blood samples for sirolimus collected for 144 hours after each dose were analyzed by liquid chromatography/tandem mass spectrometry. Pharmacokinetic parameters, assessed using noncompartmental methods, were compared using analysis of variance. Geometric mean ratios of Cmax and AUCinf were 29% (90% CI: 26, 32%) and 18% (90% CI: 16, 21%), respectively, with rifampin co-administration versus sirolimus alone. Corresponding decreases in Cmax and AUC were 71% and 82%, respectively, which would likely cause trough concentrations to fall below the recommended therapeutic range. Mean CL/F increased approximately fivefold with rifampin versus sirolimus alone. Co-administering sirolimus and potent CYP3A inducers is not recommended. If co-administration is necessary, dose adjustment and concentration monitoring should be conducted.

The influence of smoking status on the pharmacokinetics and pharmacodynamics of clopidogrel and prasugrel: the PARADOX study

OBJECTIVES

The goal of this study was to evaluate the effect of smoking on the pharmacokinetics and pharmacodynamics (PD) of clopidogrel and prasugrel therapy.

BACKGROUND

Major randomized trial data demonstrated that nonsmokers experience less or no benefit from clopidogrel treatment compared with smokers (i.e., the "smokers' paradox").

METHODS

PARADOX was a prospective, randomized, double-blind, double-dummy, placebo-controlled, crossover study of objectively assessed nonsmokers (n = 56) and smokers (n = 54) with stable coronary artery disease receiving aspirin therapy. Patients were randomized to receive clopidogrel (75 mg daily) or prasugrel (10 mg daily) for 10 days and crossed over after a 14-day washout. PD was assessed by using VerifyNow P2Y12 and vasodilator-stimulated phosphoprotein phosphorylation assays. Clopidogrel and prasugrel metabolite levels, cytochrome P450 1A2 activity, CYP2C19 genotype, and safety parameters were determined.

RESULTS

During clopidogrel therapy, device-reported inhibition of platelet aggregation (IPA) trended lower in nonsmokers than smokers (least squares mean treatment difference ± SE: 7.7 ± 4.1%; p = 0.062). Device-reported IPA was significantly lower in clopidogrel-treated smokers than prasugrel-treated smokers (least squares mean treatment difference: 31.8 ± 3.4%; p < 0.0001). During clopidogrel therapy, calculated IPA was lower and P2Y12 reaction units and vasodilator-stimulated phosphoprotein phosphorylation and platelet reactivity index were higher in nonsmokers than in smokers (p = 0.043, p = 0.005, and p = 0.042, respectively). Greater antiplatelet effects were present after prasugrel treatment regardless of smoking status (p < 0.001 for all comparisons).

CONCLUSIONS

PARADOX demonstrated lower clopidogrel active metabolite exposure and PD effects of clopidogrel in nonsmokers relative to smokers. Prasugrel was associated with greater active metabolite exposure and PD effects than clopidogrel regardless of smoking status. The poorer antiplatelet response in clopidogrel-treated nonsmokers may provide an explanation for the smokers' paradox. (The Influence of Smoking Status on Prasugrel and Clopidogrel Treated Subjects Taking Aspirin and Having Stable Coronary Artery Disease; NCT01260584).

Antihypertensive and Metabolic Effects of Concomitant Administration of Terazosin and Methyclothiazide for the Treatment of Essential Hypertension

The efficacy and safety of once-daily 2.5- or 5.0-mg methyclothiazide (MCTZ) added to once-daily 5.0-mg terazosin (TRZ) versus 5.0-mg TRZ alone was evaluated in this double-blind, multicenter study. All patients received TRZ during a 6-week titration period. Hypertensive patients (222) (mean blood pressure of 159/104 mm Hg) were randomized to one of three treatment groups: TRZ alone (N = 76); TRZ+MCTZ-2.5 mg (N = 74); and TRZ+MCTZ-5.0 mg (N = 72) for the 8-week double-blind period. Changes in the supine and standing SBP/DBP from preTRZ period were: TRZ alone (-4.8/-8.1 and -2.6/-6.1 mm Hg); TRZ+MCTZ-2.5 mg (-17.3/-12.4 and -16.0/-11.2 mm Hg); and TRZ+MCTZ-5.0 mg (-20.6/-14.4 and -23.3/-14.6 mm Hg). Blood pressure changes in the combination groups were significantly greater than those in the TRZ alone group. However, there were no statistically significant differences between the TRZ+MCTZ-2.5-mg and TRZ+MCTZ-5.0-mg groups. The combination of TRZ and MCTZ tends to mitigate the adverse effects on serum glucose, uric, potassium and lipids usually associated with thiazide diuretics. Thus, combination treatment that begins with TRZ and adds MCTZ is effective in lowering blood pressure without any significant adverse metabolic effects.

Pharmacokinetics of Long-Acting Naltrexone in Subjects With Mild to Moderate Hepatic Impairment

Long-acting naltrexone is an extended-release formulation developed with the goal of continuous naltrexone exposure for 1 month for the treatment of alcohol dependence. The influence of mild and moderate hepatic impairment on naltrexone pharmacokinetics following long-acting naltrexone 190-mg administration was assessed. Subjects with mild (Child-Pugh grade A) and moderate (Child-Pugh grade B) hepatic impairment (n = 6 per group) and matched control subjects (n = 13) were enrolled. Naltrexone and 6beta-naltrexol concentrations were determined over a period of 63 days following a single intramuscular dose. Naltrexone and 6beta-naltrexol concentrations were detected in all subjects through 28 days. Total exposure (AUC(0-infinity)) of naltrexone and 6beta-naltrexol was similar across all groups. The long apparent half-lives of naltrexone and 6beta-naltrexol (5-8 days) were attributed to the slow release of naltrexone (long-acting naltrexone exhibits absorption rate-limited elimination or "flip-flop" kinetics); elimination was not altered in subjects with hepatic impairment. Based on pharmacokinetic considerations, the dose of long-acting naltrexone does not need to be adjusted in patients with mild or moderate hepatic impairment.

Tolerability of Fosaprepitant and Bioequivalency to Aprepitant in Healthy Subjects

Fosaprepitant is an intravenous formulation of aprepitant, an oral NK1 antagonist used to prevent chemotherapy-induced nausea and vomiting. This randomized study was designed to evaluate fosaprepitant in polysorbate 80 vehicle for tolerability and bioequivalency to aprepitant. Tolerability was assessed by physical and laboratory examinations and adverse events. Plasma collected for 72 hours was assayed for aprepitant and fosaprepitant. Analysis of variance models were applied to natural log-transformed aprepitant area under the curve (AUC) data. Fosaprepitant up to 150 mg (1 mg/mL) was generally well tolerated. Fosaprepitant 115 mg was AUC bioequivalent to aprepitant 125 mg; the 90% confidence interval for the geometric mean ratio of aprepitant AUC for fosaprepitant 115 mg/aprepitant 125 mg fell within prespecified equivalence bounds of 0.80 to 1.25.

FTY720 Pharmacokinetics in Mild to Moderate Hepatic Impairment

The influence of mild and moderate hepatic impairment on FTY720 pharmacokinetics was assessed. The authors enrolled 32 subjects consisting of 8 with mild and 8 with moderate hepatic impairment based on Child-Pugh criteria and 16 demographically matched control subjects. A single 1-mg oral dose of FTY720 was administered under fasting conditions. Blood, plasma, and urine samples were obtained over a 14-day period for measurement of FTY720 and metabolite concentrations and protein binding. Total blood lymphocyte counts and heart rate were serially monitored to assess pharmacologic responses to FTY720. Peak FTY720 blood concentrations were similar across groups. Oral clearance (CL/F) was reduced 10% in mild hepatic impairment (P = .493) and 31% in moderate hepatic impairment (P = .034). There were no significant differences in blood exposure to the hexanoic or butanoic acid metabolites among groups. The effect of FTY720 on blood lymphocytes was similar across groups, with a mean decrease of 44% from the predose value. Like-wise, the effect of FTY720 on supine heart rate was similar across groups, with a mean 13% decrease from the predose rate occurring 2 to 4 hours postdose and recovering within 1 to 2 days. Although hepatic impairment elicited changes in the disposition of FTY720, the magnitude of these changes suggests that the FTY720 dose does not need to be adjusted in mild or moderate hepatic-impaired patients.

Single-dose pharmacokinetics and pharmacodynamics of anacetrapib, a potent cholesteryl ester transfer protein (CETP) inhibitor, in healthy subjects

AIMS

Anacetrapib is an orally active and potent inhibitor of CETP in development for the treatment of dyslipidaemia. These studies endeavoured to establish the safety, tolerability, pharmacokinetics and pharmacodynamics of rising single doses of anacetrapib, administered in fasted or fed conditions, and to preliminarily assess the effect of food, age, gender and obesity on the single-dose pharmacokinetics and pharmacodynamics of anacetrapib.

METHODS

Safety, tolerability, anacetrapib concentrations and CETP activity were evaluated.

RESULTS

Anacetrapib was rapidly absorbed, with peak concentrations occurring at approximately 4 h post-dose and an apparent terminal half-life ranging from approximately 9 to 62 h in the fasted state and from approximately 42 to approximately 83 h in the fed state. Plasma AUC and C(max) appeared to increase in a less than approximately dose-dependent manner in the fasted state, with an apparent plateau in absorption at higher doses. Single doses of anacetrapib markedly and dose-dependently inhibited serum CETP activity with peak effects of approximately 90% inhibition at t(max) and approximately 58% inhibition at 24 h post-dose. An E(max) model best described the plasma anacetrapib concentration vs CETP activity relationship with an EC(50) of approximately 22 nm. Food increased exposure to anacetrapib; up to approximately two-three-fold with a low-fat meal and by up to approximately six-eight fold with a high-fat meal. Anacetrapib pharmacokinetics and pharmacodynamics were similar in elderly vs young adults, women vs men, and obese vs non-obese young adults. Anacetrapib was well tolerated and was not associated with any meaningful increase in blood pressure.

CONCLUSIONS

Whereas food increased exposure to anacetrapib significantly, age, gender and obese status did not meaningfully influence anacetrapib pharmacokinetics and pharmacodynamics.

Effect of moderate hepatic insufficiency on the pharmacokinetics of sitagliptin

BACKGROUND

Sitagliptin is a highly selective dipeptidyl peptidase-4 inhibitor for the treatment of patients with type 2 diabetes. Sitagliptin is primarily excreted by renal elimination as unchanged drug, with only a small percentage (approximately 16%) undergoing hepatic metabolism.

OBJECTIVES

The primary purpose of this study was to evaluate the influence of moderate hepatic insufficiency on the pharmacokinetics of sitagliptin.

METHODS

In an open-label study, a single 100-mg oral dose of sitagliptin was administered to 10 male or female patients with moderate hepatic insufficiency (Child-Pugh's scores ranged from 7 to 9) and 10 healthy control subjects matched to each patient for race, gender, age (+/- 5 yrs) and body mass index (BMI kg/m2 +/- 5%). After administration of each dose, blood and urine samples were collected to assess sitagliptin pharmacokinetics.

RESULTS

The mean AUC(0-infinity) and Cmax for sitagliptin were numerically, but not significantly (p>0.050), higher in patients with moderate hepatic insufficiency compared with healthy matched control subjects by 21% and 13%, respectively. These slight differences were also not considered to be clinically meaningful. Moderate hepatic insufficiency had no statistically significant effect on the Tmax, apparent terminal t(1/2), fraction of the oral dose excreted into urine (f(e,0-infinity)) and renal clearance (ClR) (p>0.100) of sitagliptin. Sitagliptin was generally well tolerated by both patients and subjects; all adverse experiences were transient and rated as mild in intensity.

CONCLUSIONS

Moderate hepatic insufficiency has no clinically meaningful effect on the pharmacokinetics of sitagliptin.

Ketoconazole increases fingolimod blood levels in a drug interaction via CYP4F2 inhibition

The sphingosine-1-phosphate receptor modulator fingolimod is predominantly hydroxylated by cytochrome CYP4F2. In vitro experiments showed that ketoconazole significantly inhibited the oxidative metabolism of fingolimod by human liver microsomes and by recombinant CYP4F2. The authors used ketoconazole as a putative CYP4F2 inhibitor to quantify its influence on fingolimod pharmacokinetics in healthy subjects. In a 2-period, single-sequence, crossover study, 22 healthy subjects received a single 5-mg dose of fingolimod in period 1. In period 2, subjects received ketoconazole 200 mg twice daily for 9 days and a single 5-mg dose of fingolimod coadministered on the 4th day of ketoconazole treatment. Ketoconazole did not affect fingolimod t(max) or half-life, but there was a weak average increase in C(max) of 1.22-fold (90% confidence interval, 1.15-1.30). The AUC over the 5 days of ketoconazole coadministration increased 1.40-fold (1.31-1.50), and the full AUC to infinity increased 1.71-fold (1.53-1.91). The AUC of the active metabolite fingolimod-phosphate was increased to a similar extent by 1.67-fold (1.50-1.85). Ketoconazole predose plasma levels were not altered by fingolimod. The magnitude of this interaction suggests that a proactive dose reduction of fingolimod is not necessary when adding ketoconazole to a fingolimod regimen. The clinician, however, should be aware of this interaction and bear in mind the possibility of a fingolimod dose reduction based on clinical monitoring.

Influence of taranabant, a cannabinoid-1 receptor inverse agonist, on pharmacokinetics and pharmacodynamics of warfarin

INTRODUCTION

The pharmacokinetic/pharmacodynamic effects of warfarin were assessed in the presence and absence of taranabant, an orally active, highly selective, potent, cannabinoid-1 receptor inverse agonist, which was being developed for the treatment of obesity.

METHODS

Twelve subjects were assigned to two open-label treatments in fixed sequence separated by a 14-day washout. Treatment A was single-dose warfarin 30 mg on day 1. Treatment B was multiple-dose taranabant 6 mg each day for 21 days (days -14 to day 7) with coadministration of singledose warfarin 30 mg on day 1. Blood samples were collected predose and up to 168 hours postdose for assay of R(+)-and S(-)-warfarin and prothrombin time/international normalized ratio (PT/INR).

RESULTS

The geometric mean ratios (GMR; warfarin+taranabant/warfarin 90% confidence interval [CI] primary endpoints) for area under the curve (AUC)(0-infinity) for R(+)-and S(-)-warfarin were 1.10 (90% CI: 1.03, 1.18) and 1.06 (90% CI: 1.00, 1.13), respectively. The GMRs (warfarin+taranabant/warfarin) for the maximum plasma concentration (C(max)) of S(-)-and R(+)-warfarin were 1.16 (90% CI: 1.05, 1.28) and 1.17 (90% CI: 1.07, 1.29), respectively. For R(+)-and S(-)-warfarin, the 90% CIs for AUC(0-infinity) GMRs fell within the prespecified bounds. Taranabant did not produce a clinically meaningful effect on PT/INR.

CONCLUSION

No clinically significant alterations of the pharmacokinetics of R(+)-and S(-)-warfarin were seen following coadministration of multipledose taranabant 6 mg and single-dose warfarin 30 mg.

Lack of a significant drug interaction between raltegravir and tenofovir

Raltegravir is a novel human immunodeficiency virus type 1 (HIV-1) integrase inhibitor with potent in vitro activity (95% inhibitory concentration of 31 nM in 50% human serum). This article reports the results of an open-label, sequential, three-period study of healthy subjects. Period 1 involved raltegravir at 400 mg twice daily for 4 days, period 2 involved tenofovir disoproxil fumarate (TDF) at 300 mg once daily for 7 days, and period 3 involved raltegravir at 400 mg twice daily plus TDF at 300 mg once daily for 4 days. Pharmacokinetic profiles were also determined in HIV-1-infected patients dosed with raltegravir monotherapy versus raltegravir in combination with TDF and lamivudine. There was no clinically significant effect of TDF on raltegravir. The raltegravir area under the concentration time curve from 0 to 12 h (AUC(0-12)) and peak plasma drug concentration (C(max)) were modestly increased in healthy subjects (geometric mean ratios [GMRs], 1.49 and 1.64, respectively). There was no substantial effect of TDF on raltegravir concentration at 12 h postdose (C(12)) in healthy subjects (GMR [TDF plus raltegravir-raltegravir alone], 1.03; 90% confidence interval [CI], 0.73 to 1.45), while a modest increase (GMR, 1.42; 90% CI, 0.89 to 2.28) was seen in HIV-1-infected patients. Raltegravir had no substantial effect on tenofovir pharmacokinetics: C(24), AUC, and C(max) GMRs were 0.87, 0.90, and 0.77, respectively. Coadministration of raltegravir and TDF does not change the pharmacokinetics of either drug to a clinically meaningful degree. Raltegravir and TDF may be coadministered without dose adjustments.

Effect of sitagliptin, a dipeptidyl peptidase-4 inhibitor, on blood pressure in nondiabetic patients with mild to moderate hypertension

The effect of sitagliptin, a dipeptidyl peptidase-4 inhibitor, on ambulatory blood pressure was assessed in nondiabetic patients with mild to moderate hypertension in a randomized, double-blind, placebo-controlled, 3-period crossover study. Nineteen patients on stable treatment with antihypertensive agent(s) received sitagliptin 100 mg b.i.d., 50 mg b.i.d., or placebo for 5 days, with at least a 7-day washout interval between periods. Twenty-four-hour ambulatory blood pressure, including systolic blood pressure, diastolic blood pressure, and mean arterial pressure, were monitored on days 1 and 5. Relative to placebo on day 1, the mean difference in 24-hour systolic blood pressure was -0.9 mm Hg (90% confidence interval: -2.9 to 1.1; P = .46) with sitagliptin 50 mg b.i.d. and -2.8 mm Hg (90% confidence interval: -4.9 to -0.8; P < .05) with 100 mg b.i.d. On day 5, the mean difference in 24-hour systolic blood pressure was -2.0 mm Hg (90% confidence interval: -3.5 to -0.4; P < .05) with 50 mg b.i.d. and -2.2 mm Hg (90% confidence interval: -3.7 to -0.6; P < .05) with 100 mg b.i.d. relative to placebo. For 24-hour diastolic blood pressure, there were no between-group differences in mean 24-hour diastolic blood pressure on day 1. On day 5, sitagliptin 50 mg and 100 mg b.i.d significantly (P < .05) lowered mean 24-hour diastolic blood pressure by -1.8 mm Hg (90% confidence interval: -2.8 to -0.8) and -1.6 mm Hg (90% confidence interval: -2.6 to -0.7), respectively, relative to placebo. Sitagliptin produced small but statistically significant reductions of 2 mm Hg to 3 mm Hg in 24-hour ambulatory blood pressure measurements acutely (day 1) and at steady state (day 5), and was generally well tolerated in nondiabetic patients with mild to moderate hypertension.

Single- and multiple-dose administration of caspofungin in patients with hepatic insufficiency: implications for safety and dosing recommendations

This report investigated safety and dosing recommendations of intravenous caspofungin in hepatic insufficiency. In the single-dose study, 8 patients each with mild and moderate hepatic insufficiency received 70 mg of caspofungin. In the multiple-dose study, 8 patients with mild hepatic insufficiency and 13 healthy matched controls received 70 mg on day 1 and 50 mg daily on days 2 through 14. Eight patients with moderate hepatic insufficiency received 70 mg on day 1 and 35 mg daily on days 2 through 14. Caspofungin was generally well tolerated with no discontinuations due to serious or nonserious adverse experiences. The area under the concentration-time profile over the interval of last quantifiable point to infinity (AUC(0-infinity)) geometric mean ratio (GMR) (90% confidence interval [CI]) for mild hepatic insufficiency/historical controls was 1.55 (1.32-1.86) in the single-dose study and for mild hepatic insufficiency/concurrent controls was 1.21 (1.04-1.39) for day 14 area under the concentration-time profile calculated over the interval 0 to 24 hours (AUC(0-24h)) following multidose. The AUC(0-infinity) GMR (90% CI) for moderate hepatic insufficiency/historical controls was 1.76 (1.51-2.06) following 70 mg; AUC(0-24h) GMR (90% CI) for moderate hepatic insufficiency/concurrent controls was 1.07 (0.90-1.28) on day 14 after 35 mg daily. No dosage adjustment is recommended for patients with mild hepatic insufficiency. A dosage reduction to 35 mg daily following the 70-mg loading dose is recommended for patients with moderate hepatic insufficiency.

Safety, Tolerability, and Pharmacokinetics of Raltegravir After Single and Multiple Doses in Healthy Subjects

Raltegravir is a novel human immunodeficiency virus-1 integrase inhibitor with potent in vitro activity (95% inhibitory concentration (IC95)=33 nM in 50% human serum). Three double-blind, randomized, placebo-controlled, pharmacokinetic, safety, and tolerability studies were conducted: (1) single-dose escalation study (10-1,600 mg), (2) multiple-dose escalation study (100-800 mg q12 h x 10 days), and (3) single-dose female study (400 mg). Raltegravir was rapidly absorbed with a terminal half-life (t1/2) approximately 7-12 h. Approximately 7-14% of raltegravir was excreted unchanged in urine. Area under the curve (AUC)(0-infinity) was similar between male and female subjects. After multiple-dose administration, steady state was achieved within 2 days; there was little to modest accumulation of raltegravir. Trough levels were >33 nM for dose levels of 100 mg and greater. Raltegravir is generally well tolerated at doses of up to 1,600 mg/day given for up to 10 days and exhibits a pharmacokinetic profile supportive of twice-daily dosing with multiple doses of 100 mg and greater achieving trough levels >33 nM.

Pharmacokinetic evaluation of rofecoxib : comparison of tablet and suspension formulations

OBJECTIVE

Rofecoxib suspension is a formulation developed to increase the convenience of rofecoxib therapy for patients who have difficulty swallowing tablets. This open-label, two-part study compared the single-dose pharmacokinetics of rofecoxib tablets and rofecoxib suspension in healthy subjects.

DESIGN AND STUDY PARTICIPANTS

Part I was a two-period crossover study that assessed the bioequivalence of the 12.5mg/5mL rofecoxib suspension and the 12.5mg rofecoxib tablet in 24 healthy subjects (12 men and 12 women). Part II was a crossover study in 24 additional healthy subjects (12 men and 12 women) that determined the bioequivalence of the rofecoxib 25mg/5mL suspension and the 25mg rofecoxib tablet.

RESULTS

No clinically meaningful differences between rofecoxib tablet and suspension were apparent with respect to the rofecoxib area under the concentration-time curve from time zero to infinity (AUC(0-infinity)) and maximum plasma concentration (C(max)), the primary measures of bioequivalence. At the 12.5mg and 25mg doses, the 90% CI for the geometric mean ratio (suspension/tablet) of both AUC(0-infinity) and C(max) fell within the prespecified interval for bioequivalence (0.80-1.25).

CONCLUSIONS

The rofecoxib suspension is bioequivalent to the rofecoxib tablet at single oral doses of 12.5mg and 25mg in healthy volunteers. The convenience and ease of administration of rofecoxib suspension may translate into increased compliance with therapy compared with a conventional solid tablet formulation, particularly for elderly patients.

The influence of hepatic impairment on the pharmacokinetics of the dipeptidyl peptidase IV (DPP-4) inhibitor vildagliptin

OBJECTIVE

Vildagliptin is a potent and selective dipeptidyl peptidase-IV (DPP-4) inhibitor that improves glycemic control in patients with type 2 diabetes mellitus by increasing alpha- and beta-cell responsiveness to glucose. This study investigated the pharmacokinetics of vildagliptin in patients with hepatic impairment compared with healthy subjects.

METHODS

This was an open-label, parallel-group study in patients with mild (n = 6), moderate (n = 6) or severe (n = 4) hepatic impairment and healthy subjects (n = 6). All subjects received a single 100-mg oral dose of vildagliptin, and plasma concentrations of vildagliptin and its main pharmacologically inactive metabolite LAY151 were measured up to 36 h post-dose.

RESULTS

Exposure to vildagliptin (AUC(0-infinity) and C(max)) decreased non-significantly by 20 and 30%, respectively, in patients with mild hepatic impairment [geometric mean ratio (90% CI): AUC(0-infinity), 0.80 (0.60, 1.06), p = 0.192; C(max), 0.70 (0.46, 1.05), p = 0.149]. Exposure to vildagliptin was also decreased non-significantly in patients with moderate hepatic impairment [-8% for AUC(0-infinity), geometric mean ratio (90% CI): 0.92 (0.69, 1.23), p = 0.630; -23% for C(max), geometric mean ratio (90% CI): 0.77 (0.51, 1.17), p = 0.293]. In patients with severe hepatic impairment, C(max) was 6% lower than that in healthy subjects [geometric mean ratio (90% CI): 0.94 (0.59, 1.49), p = 0.285], whereas AUC(0-infinity) was increased by 22% [geometric mean ratio (90% CI): 1.22 (0.89, 1.68), p = 0.816). Across the hepatic impairment groups, LAY151 AUC(0-infinity) and C(max) were increased by 29-84% and 24-63%, respectively, compared with healthy subjects. The single 100-mg oral dose of vildagliptin was well tolerated by patients with hepatic impairment.

CONCLUSIONS

There was no significant difference in exposure to vildagliptin in patients with mild, moderate or severe hepatic impairment; therefore, no dose adjustment of vildagliptin is necessary in patients with hepatic impairment.

Intravenous conivaptan: effects on the QTc interval and other electrocardiographic parameters in healthy volunteers

Prolongation of the QT interval is clinically important because it may be associated with torsade de pointes, a potentially fatal arrhythmia. The objective of this study was to define the effects on electrocardiogram (ECG) of intravenous conivaptan, the first arginine vasopressin V1A/V2-receptor antagonist indicated for the treatment of euvolemic hyponatremia, on hospitalized patients without congestive heart failure. After a placebo run-in period, participants in this randomized, single-blind, placebo- and positive-controlled, parallel-group study received an intravenous 20-mg loading dose of conivaptan (day 1), followed by a 40-mg/d continuous infusion (days 1-4); a 20-mg loading dose of conivaptan (day 1), followed by an 80-mg/d continuous infusion (days 1-4); or moxifloxacin 400 mg (positive control) or placebo from day 1 to day 4. The primary ECG endpoint was QTc interval duration, which was determined by the individually corrected QT interval for each subset; secondary endpoints included QT intervals corrected with Bazett's formula and Fridericia's formula. No clinically notable changes in ECG parameters were associated with conivaptan, suggesting that conivaptan did not affect cardiac repolarization or cardiac conduction.

Effect of single oral doses of sitagliptin, a dipeptidyl peptidase-4 inhibitor, on incretin and plasma glucose levels after an oral glucose tolerance test in patients with type 2 diabetes

CONTEXT

In response to a meal, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP) are released and modulate glycemic control. Normally these incretins are rapidly degraded by dipeptidyl peptidase-4 (DPP-4). DPP-4 inhibitors are a novel class of oral antihyperglycemic agents in development for the treatment of type 2 diabetes. The degree of DPP-4 inhibition and the level of active incretin augmentation required for glucose lowering efficacy after an oral glucose tolerance test (OGTT) were evaluated.

OBJECTIVE

The objective of the study was to examine the pharmacodynamics, pharmacokinetics, and tolerability of sitagliptin.

DESIGN

This was a randomized, double-blind, placebo-controlled, three-period, single-dose crossover study.

SETTING

The study was conducted at six investigational sites.

PATIENTS

The study population consisted of 58 patients with type 2 diabetes who were not on antihyperglycemic agents.

INTERVENTIONS

Interventions included sitagliptin 25 mg, sitagliptin 200 mg, or placebo.

MAIN OUTCOME MEASURES

Measurements included plasma DPP-4 activity; post-OGTT glucose excursion; active and total incretin GIP levels; insulin, C-peptide, and glucagon concentrations; and sitagliptin pharmacokinetics.

RESULTS

Sitagliptin dose-dependently inhibited plasma DPP-4 activity over 24 h, enhanced active GLP-1 and GIP levels, increased insulin/C-peptide, decreased glucagon, and reduced glycemic excursion after OGTTs administered at 2 and 24 h after single oral 25- or 200-mg doses of sitagliptin. Sitagliptin was generally well tolerated, with no hypoglycemic events.

CONCLUSIONS

In this study in patients with type 2 diabetes, near maximal glucose-lowering efficacy of sitagliptin after single oral doses was associated with inhibition of plasma DPP-4 activity of 80% or greater, corresponding to a plasma sitagliptin concentration of 100 nm or greater, and an augmentation of active GLP-1 and GIP levels of 2-fold or higher after an OGTT.

Pharmacokinetics of sirolimus (rapamycin) in subjects with mild to moderate hepatic impairment

Eighteen adult subjects with mild to moderate hepatic impairment and 18 healthy control subjects were given a single 15-mg dose of sirolimus by oral solution. Mean whole-blood sirolimus weight-normalized oral-dose clearances (CL/F) were significantly decreased (P = .02) in subjects with mild to moderate hepatic impairment by -31.8% and -36.0%, respectively, compared with controls. There were no significant differences in mean sirolimus C(max) and t(max) values among groups. The observed decreases in CL/F may be relevant in renal transplant patients with mild to moderate hepatic impairment, based on the close similarity of sirolimus CL/F in controls and previously studied stable renal transplant patients receiving multiple-dose administration of sirolimus and cyclosporine. There was considerable overlap in the CL/F values of hepatic-impaired subjects and controls, suggesting that whole-blood sirolimus trough concentrations in renal transplant patients exhibiting mild to moderate hepatic impairment be initially monitored to assess the need for dose adjustments.

METABOLISM AND DISPOSITION OF A POTENT AND SELECTIVE GABA-Aα2/3 RECEPTOR AGONIST IN HEALTHY MALE VOLUNTEERS

[14C]7-(1,1-Dimethylethyl)-6-(2-ethyl-2H-1,2,4-triazol-3-ylmethoxy)-3-(2-fluorophenyl)-1,2,4-triazolo[4,3-b]pyridazine ([14C]-TPA023; 99 microCi/dose) was administered to five young, healthy, fasted male subjects as a single oral dose (3.0 mg) in solution (propylene glycol/water, 10:90 v/v). The parent compound was rapidly absorbed (plasma Tmax approximately 2 h), exhibited an apparent terminal half-life of 6.7 h, and accounted for approximately 53% of the total radioactivity in plasma. After 7 days of collection, the mean total recovery of radioactivity in the excreta was 82.6%, with 53.2% and 29.4% in urine and feces, respectively. Radiochromatographic analysis of the excreta revealed that TPA023 was metabolized extensively, and only trace amounts of unchanged parent were recovered. Radiochromatograms of urine and feces showed that TPA023 underwent metabolism via three pathways (t-butyl hydroxylation, N-deethylation, and direct N-glucuronidation). The products of t-butyl hydroxylation and N-deethylation, together with their corresponding secondary metabolites, accounted for the majority of the radioactivity in the excreta. In addition, approximately 10.3% of the dose was recovered in urine as the triazolo-pyridazine N1-glucuronide of TPA023. The t-butyl hydroxy and N-desethyl metabolites of TPA023, the TPA023 N1-glucuronide, and the triazolo-pyridazine N1-glucuronide of N-desethyl TPA023 were present in plasma. In healthy male subjects, therefore, TPA023 is well absorbed and is metabolized extensively (t-butyl hydroxylation and N-deethylation > glucuronidation), and the metabolites are excreted in urine and feces.

Single- and Multiple-Dose Pharmacokinetics of Long-acting Injectable Naltrexone

BACKGROUND

Oral naltrexone is effective in the treatment of alcohol dependence; however, a major limitation of its clinical utility is poor patient adherence to the daily dosing schedule. A biodegradable, long-acting naltrexone microsphere formulation was developed to achieve continuous naltrexone exposure for 1 month in the treatment of alcohol dependence.

METHODS

The single- and multiple-dose safety and pharmacokinetics of a long-acting naltrexone microsphere preparation were evaluated in healthy subjects. One group of subjects (n = 28) received a single dose of oral naltrexone 50 mg followed by a single gluteal intramuscular (IM) injection of long-acting naltrexone 190 or 380 mg or placebo. A different group of subjects (n = 14) received oral naltrexone 50 mg daily for 5 days, followed by IM long-acting naltrexone 380 mg or placebo every 28 days for a total of 4 doses. A 7-day washout period separated oral and IM administrations. Blood samples were collected to determine plasma concentrations of naltrexone and the primary metabolite, 6beta-naltrexol.

RESULTS

After a single IM injection of long-acting naltrexone 380 mg, naltrexone plasma concentrations were measurable in all subjects for at least 31 days postdose. The pharmacokinetics were proportional to the dose and multiple dose observations were consistent with single dose observations. Mean apparent elimination half-lives for naltrexone and 6beta-naltrexol ranged from 5 to 7 days. Exposure to 6beta-naltrexol was reduced with IM injection compared with that oral administration. No serious adverse events occurred.

CONCLUSIONS

This study demonstrated that the long-acting naltrexone formulation was well tolerated, displayed predictable pharmacokinetics, and resulted in no meaningful drug accumulation upon multiple dosing. Intramuscular administration avoids first-pass metabolism and changes the exposure ratio of 6beta-naltrexol to naltrexone compared with oral administration. By providing continuous exposure to naltrexone for several weeks following IM injection, this long-acting naltrexone formulation may offer therapeutic benefit to those patients who experience difficulty adhering to the daily administration schedule necessitated by oral naltrexone therapy.

Bioequivalence of an ezetimibe/simvastatin combination tablet and coadministration of ezetimibe and simvastatin as separate tablets in healthy subjects

OBJECTIVE

To assess the bioequivalence of an ezetimibe/simvastatin (EZE/SIMVA) combination tablet compared to the coadministration of ezetimibe and simvastatin as separate tablets (EZE + SIMVA).

METHODS

In this open-label, randomized, 2-part, 2-period crossover study, 96 healthy subjects were randomly assigned to participate in each part of the study (Part I or II), with each part consisting of 2 single-dose treatment periods separated by a 14-day washout. Part I consisted of Treatments A (EZE 10 mg + SIMVA 10 mg) and B (EZE/SIMVA 10/10 mg/mg) and Part II consisted of Treatments C (EZE 10 mg + SIMVA 80 mg) and D (EZE/SIMVA 10/80 mg/mg). Blood samples were collected up to 96 hours post-dose for determination of ezetimibe, total ezetimibe (ezetimibe + ezetimibe glucuronide), simvastatin and simvastatin acid (the most prevalent active metabolite of simvastatin) concentrations. Ezetimibe and simvastatin acid AUC(0-last) were predefined as primary endpoints and ezetimibe and simvastatin acid Cmax were secondary endpoints. Bioequivalence was achieved if 90% confidence intervals (CI) for the geometric mean ratios (GMR) (single tablet/coadministration) of AUC(0-last) and Cmax fell within prespecified bounds of (0.80, 1.25).

RESULTS

The GMRs of the AUC(0-last) and Cmax for ezetimibe and simvastatin acid fell within the bioequivalence limits (0.80, 1.25). EZE/ SIMVA and EZE + SIMVA were generally well tolerated.

CONCLUSIONS

The lowest and highest dosage strengths of EZE/SIMVA tablet were bioequivalent to the individual drug components administered together. Given the exact weight multiples of the EZE/SIMVA tablet and linear pharmacokinetics of simvastatin across the marketed dose range, bioequivalence of the intermediate tablet strengths (EZE/SIMVA 10/20 mg/mg and EZE/SIMVA 10/40 mg/mg) was inferred, although these dosages were not tested directly. These results indicate that the safety and efficacy profile of EZE + SIMVA coadministration therapy can be applied to treatment with the EZE/SIMVA tablet across the clinical dose range.

Pharmacokinetic Considerations in Determining the Terminal Elimination Half-Lives of Bisphosphonates

BACKGROUND AND OBJECTIVE

Bisphosphonates are commonly used to treat and prevent osteoporosis. These compounds have unusual pharmacokinetic characteristics because they bind strongly to bone, and a portion becomes buried under newly formed bone. Once incorporated into bone tissue, the subsequent release during bone remodeling is probably the rate-limiting step in the terminal elimination of bisphosphonates. Because of this unique property of bisphosphonates, pharmacokinetic studies with insufficient lengths of follow-up might entirely miss the true terminal elimination phase. A terminal half-life (t((1/2)gamma)) of approximately 11 years, similar to that of calcium and other minerals in bone, was reported from an 18-month study of alendronic acid in postmenopausal women with osteoporosis. We are not aware of any other published reports in which the elimination of a bisphosphonate has been followed for more than a few weeks post-dose. The purpose of the present study was to reanalyse the alendronic acid data to examine the effect of truncating the length of follow-up on the calculated t((1/2)gamma).

PATIENTS AND METHODS

Twenty-one postmenopausal women with osteoporosis (mean age 66 years) received intravenous alendronic acid 30mg over 4 consecutive days (7.5 mg/day), and urinary excretion of alendronic acid was monitored over the following 18-24 months. Terminal elimination half-life was originally calculated by log-linear regression of the percentage retained versus time curve between days 240 and 540 and substituting the slope of the regression line into the equation, t((1/2)gamma) = -log 2/slope. These data were reanalysed based on the period up to 30 days.

RESULTS

Data were sufficient for analysis of pharmacokinetics in 11 patients. A mean t((1/2)gamma) of approximately 11 years was reported previously, based on analysis of data between days 240 and 540. Recalculating the 'terminal' half-life of alendronic acid using only data from the first 30 days resulted in an 'observed' half-life of only 11 days.

CONCLUSION

This analysis illustrates the importance of sufficient length of follow-up to accurately characterise the true terminal elimination half-life of bisphosphonates. The relatively short (expressed in units of days rather than years) terminal elimination half-lives reported for some bisphosphonates based on only 30 days of follow-up or less are likely to substantially underestimate the true terminal elimination half-lives.

Potential for interactions between caspofungin and nelfinavir or rifampin

The potential for interactions between caspofungin and nelfinavir or rifampin was evaluated in two parallel-panel studies. In study A, healthy subjects received a 14-day course of caspofungin alone (50 mg administered intravenously [IV] once daily) (n = 10) or with nelfinavir (1,250 mg administered orally twice daily) (n = 9) or rifampin (600 mg administered orally once daily) (n = 10). In study B, 14 subjects received a 28-day course of rifampin (600 mg administered orally once daily), with caspofungin (50 mg administered IV once daily) coadministered on the last 14 days, and 12 subjects received a 14-day course of caspofungin alone (50 mg administered IV once daily). The coadministration/administration alone geometric mean ratio for the caspofungin area under the time-concentration profile calculated for the 24-h period following dosing [AUC(0-24)] was as follows (values in parentheses are 90% confidence intervals [CIs]): 1.08 (0.93-1.26) for nelfinavir, 1.12 (0.97-1.30) for rifampin (study A), and 1.01 (0.91-1.11) for rifampin (study B). The shape of the caspofungin plasma profile was altered by rifampin, resulting in a 14 to 31% reduction in the trough concentration at 24 h after dosing (C(24h)), consistent with a net induction effect at steady state. Both the AUC and the C(24h) were elevated in the initial days of rifampin coadministration in study A (61 and 170% elevations, respectively, on day 1) but not in study B, consistent with transient net inhibition prior to full induction. The coadministration/administration alone geometric mean ratio for the rifampin AUC(0-24) on day 14 was 1.07 (90% CI, 0.83-1.38). Nelfinavir does not meaningfully alter caspofungin pharmacokinetics. Rifampin both inhibits and induces caspofungin disposition, resulting in a reduced C(24h) at steady state. An increase in the caspofungin dose to 70 mg, administered daily, should be considered when the drug is coadministered with rifampin.

Simvastatin does not have a clinically significant pharmacokinetic interaction with fenofibrate in humans

Simvastatin and fenofibrate are both commonly used lipid-regulating agents with distinct mechanisms of action, and their coadministration may be an attractive treatment for some patients with dyslipidemia. A 2-period, randomized, open-label, crossover study was conducted in 12 subjects to determine if fenofibrate and simvastatin are subject to a clinically relevant pharmacokinetic interaction at steady state. In treatment A, subjects received an 80-mg simvastatin tablet in the morning for 7 days. In treatment B, subjects received a 160-mg micronized fenofibrate capsule in the morning for 7 days, followed by a 160-mg micronized fenofibrate capsule dosed together with an 80-mg simvastatin tablet on days 8 to 14. Because food increases the bioavailability of fenofibrate, each dose was administered with food to maximize the exposure of fenofibric acid. The steady-state pharmacokinetics (AUC(0-24h), C(max), and t(max)) of active and total HMG-CoA reductase inhibitors, simvastatin acid, and simvastatin were determined following simvastatin administration with and without fenofibrate. Also, fenofibric acid steady-state pharmacokinetics were evaluated with and without simvastatin. The geometric mean ratios (GMRs) for AUC(0-24h) (80 mg simvastatin [SV] + 160 mg fenofibrate)/(80 mg simvastatin alone) and 90% confidence intervals (CIs) were 0.88 (0.80, 0.95) and 0.92 (0.82, 1.03) for active and total HMG-CoA reductase inhibitors. The GMRs and 90% CIs for fenofibric acid (80 mg SV + 160 mg fenofibrate/160 mg fenofibrate alone) AUC(0-24h) and C(max) were 0.95 (0.88, 1.04) and 0.89 (0.77, 1.02), respectively. Because both the active inhibitor and fenofibric acid AUC GMR 90% confidence intervals fell within the prespecified bounds of (0.70, 1.43), no clinically significant pharmacokinetic drug interaction between fenofibrate and simvastatin was concluded in humans. The coadministration of simvastatin and fenofibrate in this study was well tolerated.

The effect of gemfibrozil on the pharmacokinetics of rosuvastatin

BACKGROUND

Coadministration of statins and gemfibrozil is associated with an increased risk for myopathy, which may be due in part to a pharmacokinetic interaction. Therefore the effect of gemfibrozil on rosuvastatin pharmacokinetics was assessed in healthy volunteers. Rosuvastatin has been shown to be a substrate for the human hepatic uptake transporter organic anion transporter 2 (OATP2). Inhibition of this transporter could increase plasma concentrations of rosuvastatin. The effect of gemfibrozil on rosuvastatin uptake by cells expressing OATP2 was also examined.

METHODS

In a randomized, double-blind, 2-period crossover trial, 20 healthy volunteers were given oral doses of gemfibrozil, 600 mg, or placebo twice daily for 7 days. On the fourth morning of each dosing period, a single oral dose of rosuvastatin, 80 mg, was coadministered. Plasma concentrations of rosuvastatin, N-desmethyl rosuvastatin, and rosuvastatin-lactone were measured. In addition, the effect of gemfibrozil on the uptake of radiolabeled rosuvastatin by OATP2-transfected Xenopus oocytes was studied.

RESULTS

Gemfibrozil increased the rosuvastatin area under the plasma concentration-time curve from time 0 to the time of the last quantifiable concentration [AUC(0-t)] 1.88-fold (90% confidence interval, 1.60-2.21) and the maximum observed rosuvastatin plasma concentration (C(max)) 2.21-fold (90% confidence interval, 1.81-2.69) compared with placebo. N-desmethyl rosuvastatin AUC(0-t) and C(max) decreased by 48% and 39%, respectively. Pharmacokinetics of rosuvastatin-lactone was unchanged. The in vitro results indicate that the maximum gemfibrozil inhibition of rosuvastatin OATP2-mediated uptake was 50%; the inhibition constant for the inhibitory process was 4.0 +/- 1.3 micromol/L.

CONCLUSIONS

Gemfibrozil increased rosuvastatin plasma concentrations approximately 2-fold, which is similar to the effect of gemfibrozil on pravastatin, simvastatin acid, and lovastatin acid plasma concentrations and substantially less than the effect observed for cerivastatin. Gemfibrozil inhibition of OATP2-mediated rosuvastatin hepatic uptake may contribute to the mechanism of the drug-drug interaction. Care is warranted when gemfibrozil is coadministered with rosuvastatin and other statins.

Disposition of caspofungin: role of distribution in determining pharmacokinetics in plasma

The disposition of caspofungin, a parenteral antifungal drug, was investigated. Following a single, 1-h, intravenous infusion of 70 mg (200 microCi) of [(3)H]caspofungin to healthy men, plasma, urine, and feces were collected over 27 days in study A (n = 6) and plasma was collected over 26 weeks in study B (n = 7). Supportive data were obtained from a single-dose [(3)H]caspofungin tissue distribution study in rats (n = 3 animals/time point). Over 27 days in humans, 75.4% of radioactivity was recovered in urine (40.7%) and feces (34.4%). A long terminal phase (t(1/2) = 14.6 days) characterized much of the plasma drug profile of radioactivity, which remained quantifiable to 22.3 weeks. Mass balance calculations indicated that radioactivity in tissues peaked at 1.5 to 2 days at approximately 92% of the dose, and the rate of radioactivity excretion peaked at 6 to 7 days. Metabolism and excretion of caspofungin were very slow processes, and very little excretion or biotransformation occurred in the first 24 to 30 h postdose. Most of the area under the concentration-time curve of caspofungin was accounted for during this period, consistent with distribution-controlled clearance. The apparent distribution volume during this period indicated that this distribution process is uptake into tissue cells. Radioactivity was widely distributed in rats, with the highest concentrations in liver, kidney, lung, and spleen. Liver exhibited an extended uptake phase, peaking at 24 h with 35% of total dose in liver. The plasma profile of caspofungin is determined primarily by the rate of distribution of caspofungin from plasma into tissues.

Pharmacokinetics of etoricoxib in patients with hepatic impairment

The effect of hepatic insufficiency on the pharmacokinetics of etoricoxib, a selective inhibitor of cyclooxygenase-2, was investigated following administration of single and multiple oral doses to mild hepatic insufficiency patients (Child-Pugh score of 5 to 6), multiple oral doses to moderate hepatic insufficiency patients (Child-Pugh score of 7 to 9), and single intravenous doses to both mild and moderate hepatic insufficiency patients. A trend of decreasing systemic clearance with increasing hepatic impairment was observed. Absorption of etoricoxib was unaffected by hepatic impairment. Binding of etoricoxib to plasma proteins was also found to be unaffected by hepatic disease. Etoricoxib was generally well tolerated by patients with mild and moderate hepatic insufficiency. Together, these results support a 60-mg once-daily dosing regimen for mild hepatic insufficiency patients and a 60-mg every-other-day dosing regimen for moderate hepatic insufficiency patients. There are no clinical or pharmacokinetic data in patients with severe hepatic insufficiency (Child-Pugh score > 9).

Pharmacokinetics and Safety of Ebastine in Patients with Impaired Hepatic Function Compared with Healthy Volunteers

OBJECTIVE

To assess the differences between patients with hepatic insufficiency and healthy subjects with regard to the pharmacokinetics, cardiac safety and overall safety of ebastine and its active metabolite carebastine.

DESIGN

Open-label parallel-group study.

PARTICIPANTS

24 patients with varying degrees of hepatic insufficiency, as categorised by the Child-Pugh classification, and 12 healthy volunteers.

METHODS

Healthy subjects and patients with Child-Pugh class A (n = 8) or B (n = 8) received ebastine 20 mg once daily for 7 days. Patients with Child-Pugh class C (n = 8) [single or repeated dose] received ebastine 10 mg. Plasma concentrations of ebastine and carebastine were determined for 23.5 hours following the initial dose on day 1 and for 96 hours following the dose on day 7 by using a sensitive liquid chromatography-tandem mass spectrometry assay with a minimum quantifiable limit of 0.05 microg/L for ebastine and 1.00 microg/L for carebastine. Hepatic function was assessed by blood clearance of indocyanine green 0.5 mg/kg administered intravenously on day 2. Cardiac and overall safety parameters were monitored.

RESULTS

Overall, the pharmacokinetics of ebastine were not modified by hepatic impairment. No correlation between ebastine pharmacokinetics and hepatic function, as expressed by indocyanine green clearance, was observed. Comparison of the effective half-life of ebastine and carebastine between groups did not show relevant differences. Therefore, no apparent accumulation of ebastine occurred, and steady-state concentrations of ebastine and carebastine were predictable from single-dose pharmacokinetics both in healthy subjects and in hepatically impaired patients. Finally, no apparent difference was noted in the safety of ebastine between patients with hepatic insufficiency and healthy subjects as assessed by evaluation of adverse events, vital signs and laboratory parameters.

CONCLUSION

Ebastine can be safely administered to patients with impaired hepatic function, as no clinically important differences can be anticipated from the pharmacokinetics and safety profile of ebastine/carebastine as compared with healthy subjects. Nevertheless, the dosage used in severely impaired patients (10mg daily) was half that used in patients with mild to moderate impairment, and any comedication did not include drugs affecting liver function; in clinical practice, both these factors should be taken into account.

Pharmacokinetic comparison of fast-disintegrating and conventional tablet formulations of risperidone in healthy volunteers

BACKGROUND

Difficulties with and resistance to tablet-taking are common in all patient groups and can exacerbate compliance problems and undermine treatment efficacy. In recent years, rapidly dissolving oral drug formulations have been developed to overcome problems related to swallowing difficulties.

OBJECTIVE

The goal of this study was to evaluate the bioequivalence of a fast-disintegrating oral tablet of risperidone and the conventional oral tablet.

METHODS

This was a randomized, open-label, 2-way crossover trial in which healthy volunteers received two 0.5-mg tablets of a fast-disintegrating oral risperidone formulation and two 0.5-mg tablets of conventional oral risperidone, each in a single administration. Blood samples for pharmacokinetic analysis of the active moiety (risperidone + 9-hydroxy-risperidone), risperidone, and its active metabolite 9-hydroxy-risperidone were obtained during a 96-hour period after dosing. Safety assessments included monitoring of adverse events, hematology and biochemistry tests of the sampled blood, urinalysis, blood pressure measurements, and electrocardiography.

RESULTS

The bioequivalence assessment was based on pharmacokinetic and statistical analysis of data from 37 subjects who completed both treatment periods. The plasma concentration-time profiles of the active moiety, risperidone, and 9-hydroxy-risperidone were similar after intake of the 2 formulations. The fast-disintegrating tablet and the conventional tablet showed bioequivalence with respect to the active moiety, risperidone, and 9-hydroxy-risperidone. The 90% CIs for the mean treatment ratios of the log-transformed peak plasma concentration, area under the plasma concentration-time curve (AUC) to the last quantifiable time point, and AUC extrapolated to infinity were all within the predefined equivalence range from 80% to 125%. Twenty-eight of 50 (56%) subjects originally randomized reported adverse events, with a similar incidence for both treatments. All adverse events were mild, with somnolence and headache being the most frequently reported. No clinically relevant changes were observed in physical, biochemical, hematologic, or urinalysis variables during the study.

CONCLUSION

In this study in healthy subjects, a single administration of two 0.5-mg fast-disintegrating risperidone tablets was bioequivalent to a single administration of two 0.5-mg conventional risperidone tablets.

Single- and multiple-dose pharmacokinetics of etoricoxib, a selective inhibitor of cyclooxygenase-2, in man

The single- and multiple-dose pharmacokinetics of etoricoxib, a selective inhibitor of cyclooxygenase-2, were examined in two clinical studies. Single-dose pharmacokinetics--including dose proportionality, absolute bioavailability of the highest dose-strength (120-mg) tablet, and the effect of a high-fat meal on the bioavailability of that tablet--were investigated in a two-part, open, balanced crossover study in two panels of healthy subjects (12 per panel). Steady-state pharmacokinetics were investigated in an open-label study in which 24 healthy subjects were administered 120-mg single and multiple (once daily for 10 days) oral doses of etoricoxib tablets. The pharmacokinetics of etoricoxib were found to be consistent with linearity through doses at least twofold greater than the highest anticipated clinical dose of 120 mg. Etoricoxib administered as a tablet was rapidly and completely absorbed and available; the absolute bioavailability was estimated to be 100%. A high-fat meal decreased the rate of absorption without affecting the extent of absorption of etoricoxib; therefore, etoricoxib can be dosed irrespective of food. Steady-state pharmacokinetics of etoricoxib, achieved following 7 days of once-daily dosing, were found to be reasonably predicted from single doses. The accumulation ratio averaged 2.1, and the corresponding accumulation t1/2 averaged 22 hours, supporting once-daily dosing. Etoricoxib was generally well tolerated.