Multiple-dose Pharmacokinetic Profiles Research Articles

First-in-human safety, tolerability, and pharmacokinetic results of DFV890, an oral low-molecular-weight NLRP3 inhibitor.

This first-in-human study evaluated the safety, tolerability, single- and multiple-dose pharmacokinetic profiles with dietary influence, and pharmacodynamics (PD) of DFV890, an oral NLRP3 inhibitor, in healthy participants. In total, 122 participants were enrolled into a three-part trial including single and 2-week multiple ascending oral doses (SAD and MAD, respectively) of DFV890, and were randomized (3:1) to DFV890 or placebo (SAD [3-600 mg] and MAD [fasted: 10-200 mg, once-daily or fed: 25 and 50 mg, twice-daily]). DFV890 was generally well-tolerated. Neither deaths nor serious adverse events were reported. A less than dose-proportional increase in exposure was observed with the initially used crystalline suspension (3-300 mg); however, an adjusted suspension formulation using spray-dried dispersion (SDD; 100-600 mg) confirmed dose-proportional increase in exposure. Relative bioavailability between crystalline suspension and tablets, and food effect were evaluated at 100 mg. Under fasting conditions, Cmax of the tablet yielded 78% compared with the crystalline suspension, and both formulations showed comparable AUC. The fed condition led to a 2.05- and 1.49-fold increase in Cmax and AUC0-last compared with the fasting condition. The median IC50 and IC90 for ex-vivo lipopolysaccharide-stimulated interleukin IL-1β release inhibition (PD) were 61 (90% CI: 50, 70) and 1340 ng/mL (90% CI: 1190, 1490). Crystalline tablets of 100 mg once-daily or 25 mg twice-daily were sufficient to maintain ~90% of the IL-1β release inhibition over 24 h at steady state. Data support dose and formulation selection for further development in diseases, in which an overactivated NLRP3 represents the underlying pathophysiology.

Lorlatinib in previously treated anaplastic lymphoma kinase‐rearranged non–small cell lung cancer: Japanese subgroup analysis of a global study

Lorlatinib is a potent, brain‐penetrant, third‐generation anaplastic lymphoma kinase (ALK)/ROS proto‐oncogene 1 (ROS1) tyrosine kinase inhibitor (TKI) that is active against most known resistance mutations. This is an ongoing phase 1/2, multinational study (NCT01970865) investigating the efficacy, safety and pharmacokinetics of lorlatinib in ALK‐rearranged/ROS1‐rearranged advanced non–small cell lung cancer (NSCLC) with or without intracranial (IC) metastases. Because patterns of ALK TKI use in Japan differ from other regions, we present a subgroup analysis of Japanese patients. Patients were enrolled into six expansion (EXP) cohorts based on ALK/ROS1 mutation status and treatment history. The primary endpoint was the objective response rate (ORR) and the IC‐ORR based on independent central review. Secondary endpoints included pharmacokinetic evaluations. At data cutoff, 39 ALK‐rearranged/ROS1‐rearranged Japanese patients were enrolled across the six expansion cohorts; all received lorlatinib 100 mg once daily. Thirty‐one ALK‐rearranged patients previously treated with ≥1 ALK TKI (EXP2 to EXP5) were evaluable for ORR and 15 were evaluable for IC‐ORR. The ORR and the IC‐ORR for Japanese patients in EXP2‐5 were 54.8% (95% confidence interval [CI]: 36.0‐72.7) and 46.7% (95% CI: 21.3‐73.4), respectively. Among patients who had received prior alectinib only (EXP3B), the ORR was 42.9%; 95% CI: 9.9‐81.6). The most common treatment‐related adverse event (TRAE) was hypercholesterolemia (79.5%). Hypertriglyceridemia was the most common grade 3/4 TRAE (25.6%). Single‐dose and multiple‐dose pharmacokinetic profiles among Japanese patients were similar to those in non–Japanese patients. Lorlatinib showed clinically meaningful responses and IC responses among ALK‐rearranged Japanese patients with NSCLC who received ≥1 prior ALK TKI, including meaningful responses among those receiving prior alectinib only. Lorlatinib was generally well tolerated.

Investigating Transporter-Mediated Drug-Drug Interactions Using a Physiologically Based Pharmacokinetic Model of Rosuvastatin.

Rosuvastatin is a frequently used probe in transporter‐mediated drug‐drug interaction (DDI) studies. This report describes the development of a physiologically based pharmacokinetic (PBPK) model of rosuvastatin for prediction of pharmacokinetic (PK) DDIs. The rosuvastatin model predicted the observed single (i.v. and oral) and multiple dose PK profiles, as well as the impact of coadministration with transporter inhibitors. The predicted effects of rifampin and cyclosporine (6.58‐fold and 5.07‐fold increase in rosuvastatin area under the curve (AUC), respectively) were mediated primarily via inhibition of hepatic organic anion‐transporting polypeptide (OATP)1B1 (Inhibition constant (Ki) ∼1.1 and 0.014 µM, respectively) and OATP1B3 (Ki ∼0.3 and 0.007 µM, respectively), with cyclosporine also inhibiting intestinal breast cancer resistance protein (BCRP; Ki ∼0.07 µM). The predicted effects of gemfibrozil and its metabolite were moderate (1.88‐fold increase in rosuvastatin AUC) and mediated primarily via inhibition of hepatic OATP1B1 and renal organic cation transporter 3. This model of rosuvastatin will be useful in prospectively predicting transporter‐mediated DDIs with novel pharmaceutical agents in development.

Pharmacokinetic Properties of Once-Daily Oral Low-Dose Mesylate Salt of Paroxetine (LDMP 7.5 mg) Following Single and Multiple Doses in Healthy Postmenopausal Women

BackgroundLow-dose mesylate salt of paroxetine (LDMP 7.5 mg) is being investigated for the treatment of vasomotor symptoms associated with menopause. ObjectiveThis Phase I, open-label, single- and multiple-dose study evaluated the pharmacokinetic properties, safety and tolerability of LDMP in postmenopausal, nonsmoking women aged ≥40 years. MethodsAfter a 3-week screening period, subjects received LDMP 7.5-mg capsules as a single dose on day 1 and then as multiple doses (once daily for 14 days) on Days 6–19. Blood samples were collected predose and up to 120 hours postdose on day 1 (single-dose pharmacokinetic profile), at predose (after 12 doses) on day 18, and at predose and up to 24 hours postdose on day 19 (multiple-dose pharmacokinetic profile). Capsules were taken with 240 mL of water while subjects were fasted. Safety was evaluated throughout the study. ResultsTwenty-four women (mean age, 56 years) completed the study. On day 1, median Tmax was ~6 hours, and mean t1/2 was 17.30 hours. Mean plasma concentrations attained predose on days 18 and 19 (days 13 and 14 of multiple dosing) and at 24 hours postdose (day 20) were similar, suggesting that steady state was achieved by day 13 of multiple dosing after 12 daily doses. Mean AUC0–24 h at steady state (day 14 of multiple dosing) was ~3-fold greater than AUC0–∞ on day 1, indicating nonlinear pharmacokinetics. Mean Cmax on day 14 of multiple dosing was ~5-fold greater than that attained on day 1, and the accumulation index (AUCday 19/AUCday 1) at steady state was 9.71. Fluctuation index (calculated as [(Cmax – Cmin)/Cavg ss] × 100) was 75.8%. Most subjects (23/24 [95.8%]) experienced at least 1 treatment-emergent adverse event (AE); however, most AEs (67 events in 22/24 subjects [91.7%]) were mild, and the remainder were moderate. Seventeen subjects experienced 33 AEs that were deemed possibly or probably related to LDMP. No serious AEs were reported, and no clinically meaningful changes in laboratory values, vital signs, or ECGs were observed. ConclusionsOn multiple dosing, LDMP exhibited nonlinear pharmacokinetics and was well tolerated in these healthy postmenopausal women; the extent of accumulation was consistent with data from the published literature. ClinicalTrials.gov identifier: NCT01829919.

Single- and Multiple-Dose Pharmacokinetics of a Novel Tetramethylpyrazine Reservoir-Type Transdermal Patch <i>versus</i> Tetramethylpyrazine Phosphate Oral Tablets in Healthy Normal Volunteers, and <i>in Vitro</i>/<i>in Vivo</i> Correlation

A novel reservoir-type transdermal system of 2,3,5,6-tetramethylpyrazine (TMP) was developed containing eucalyptus oil as a penetration enhancer. The single and multiple-dose pharmacokinetic profiles of TMP administrated by TMP transdermal patch were characterized in healthy volunteers using an in vivo, randomized, open-label, two-way crossover design. 2,3,5,6-Tetramethylpyrazine phosphate (TMPP) oral tablets were chosen as reference. Following single/multiple oral administration of 200/100 mg TMPP tablets, a TMP C(max) of 1284/613.5 ng/mL was observed within 0.75 h. Single/multiple applications of the TMP patch yielded mean C(max) of 309/325 ng/mL at a median T(max) of 5/4 h, with steady state achieved at second application. The mean C(min) of the patch was 131±30.38 ng/mL, contrasting to nearly zero for the tablet. Multiple applications of patch produced an accumulative effect over single application. At steady state 250 mg/20 cm(2) TMP patch given daily provided comparable exposure to 100 mg TMPP tablets three times daily (3753.91 versus 3563.67 ng·h/mL). TMP tablets and patch yielded similar steady-state plasma concentrations: C(av) (148.48±51.27, 156.41±40.31 ng/mL). The results demonstrated that TMP patch can achieve a therapeutic effect that is comparable to oral administration, exhibited prolonged and sustained plasma levels, fewer drug fluctuations, lower adverse effects, more convenience, and improved patient compliance. In-vitro permeation through human skin demonstrated zero-order kinetics with the flux of 364 µg/cm(2)/h. The predicted C(av) (163.9 ng/mL) was in agreement with the observed C(av) (156.4 ng/mL).

Pharmacokinetic study of single and multiple oral administrations of 2 mg dienogest in healthy Korean women

BackgroundThe progestin dienogest was developed for oral contraception, endometriosis treatment and menopause management. Dienogest's pharmacokinetics have been primarily studied in Caucasian women. This study evaluated the single- and multiple-dose pharmacokinetics of dienogest in Korean women. Study DesignSixteen healthy Korean adult women received a single administration of 2 mg dienogest, followed by multiple once-daily administrations for 14 days. The single-dose administration and the final dose of the multiple administrations were each followed by blood sampling over 60 h. ResultsThe mean (SD) maximum serum concentration after multiple doses of dienogest was slightly increased compared with that after a single dose [from 51.6 (9.6) to 56.6 (11.9) ng/mL], as was the area under the concentration–time curves (AUC)0–24h [from 503 (56.3) to 613 (90.7) ng∙h/mL]. The linearity factor calculated by AUCs of single and multiple doses is 1.00±0.14, and the terminal half-life remained unchanged when single dosing and multiple dosing were compared. ConclusionsThe present study described the single- and multiple-dose pharmacokinetic profiles of dienogest in Korean women and showed linear pharmacokinetics of dienogest at steady state.

Effect of Telavancin on the Pharmacokinetics of the Cytochrome P450 3A Probe Substrate Midazolam: A Randomized, Double‐Blind, Crossover Study in Healthy Subjects

To examine the effect of telavancin, a lipoglycopeptide antibiotic with potent gram-positive activity, on the pharmacokinetics of midazolam, a cytochrome P450 (CYP) 3A probe substrate. Design. Phase I, randomized, double-blind, placebo-controlled, crossover study. Setting. Clinical research center. Sixteen healthy adult volunteers. Intervention. Subjects were randomly assigned to receive an intravenous infusion of telavancin 10 mg/kg or placebo once/day for 7 days. On day 7, a single dose of intravenous midazolam 1 mg was given immediately after completion of the last infusion of telavancin or placebo. Patients crossed over to the alternate treatment regimen after a washout period of at least 7 days. Pharmacokinetic sampling was performed on study days 7 and 21. Blood was collected before telavancin or placebo dosing and at 0.25, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, and 24 hours after midazolam administration. Formal equivalence analysis using the two one-sided t test method showed that the geometric mean ratios for maximum plasma concentration (C(max)) and areas under the plasma concentration-time curve (AUC) for midazolam coadministered with telavancin versus midazolam coadministered with placebo were close to unity. The 90% confidence intervals (CIs) around the ratios fell within the 0.8-1.25 bioequivalence bounds (geometric mean ratio for AUC from time zero to the last measured plasma concentration 0.95, 90% CI 0.910-0.984; C(max) geometric mean ratio 1.03, 90% CI 0.956-1.11). The multiple-dose pharmacokinetic profile of telavancin with concomitant administration of midazolam (C(max) 97 microg/ml, concentration 24 hrs after completion of telavancin infusion 9 microg/ml, terminal-phase elimination half-life 8.9 hrs, clearance 13.3 ml/hr/kg) was consistent with data from earlier studies. These pharmacokinetic data show that intravenous telavancin administered at the intended therapeutic dose does not affect the pharmacokinetics of intravenous midazolam. The results indicate that telavancin is unlikely to inhibit hepatic CYP3A activity to a clinically meaningful extent.

Single- and multiple-dose pharmacokinetics of genistein capsules in healthy chinese subjects: A phase I, randomized, open-label study

Background: Genistein capsules are currently being developed to treat osteoporosis in China. Genistein is extracted from the fruit of Sophora japonica Leguminosae. Objective: The objective of this study was to assess the pharmacokinetics of genistein capsules after single and multiple oral doses in healthy Chinese subjects. Methods: This was a Phase I, randomized, open-label, single- and multiple- dose study in healthy Chinese adults (aged 19–40 years). In the single-dose study, subjects were randomly assigned in a 1:1:1 ratio to receive genistein 50, 100, or 300 mg (in 50-mg capsules). To assess the effect of food on the pharmacokinetics, subjects in the 50-mg group were equally randomized again into fasting and postprandial (genistein was administered after a high-fat breakfast) groups according to a 2-way cross-over design. A separate equal-sized group of subjects were administered genistein 50 mg on day 1 (single dose), received no treatment on days 2 and 3, and were administered genistein 50 mg QD for 6 days (days 4–9) to obtain a multiple-dose pharmacokinetic profile. Because genistein is converted so rapidly and completely to glucuronidated genistein after administration, plasma concentrations of glucuronidated genistein were determined using a validated high-performance liquid chromatography/ tandem mass spectrometry method. Drug tolerability was assessed by monitoring adverse events (AEs) and laboratory parameters. Results: The study enrolled 40 healthy subjects (24 men, 16 women; 10 each in the 50-, 100-, and 300-mg single-dose groups and 10 in the multiple-dose group). Three subjects voluntarily withdrew (2 in the 100-mg group and 1 in the 300-mg group) before study drug administration. Thirty-seven subjects (24 men, 13 women) completed the study and were included in the analysis. The mean (SD) values of the single-dose genistein 50-, 100-, and 300-mg groups were as follows: T max, 6.0 (2.4), 7.4 (2.4), and 5.6 (1.2) hours, respectively; t l/2, 13.0 (4.0), 12.6 (5.8), and 9.4 (1.1) hours; AUC 0−t, 3344 (1635), 8389 (5164), and 9361 (2428) ng/mL · h −1; and C max , 218.7 (68.6), 435.7 (202.1), and 553.4 (152.8) ng/mL. The plasma glucuronidated genistein concentrations were directly proportional to the administered dose over the range of 50 to 100 mg and increased nonproportionately with the 300-mg dose. No statistically significant differences in pharmacokinetic parameters were found in the fasting group compared with the postprandial group. In the multiple-dose group, the mean (SD) steady-state pharmacokinetic parameters on day 9 were similar to those following a single dose of genistein on day 1 (T max, 6.0 [1.0] vs 5.9 [1.5] hours, respectively; t l/2, 9.5 [1.5] vs 9.1 [1.5] hours; AUC 0−t, 2830 [1541] vs 2078 [1308] ng/mL · h −1; C max, 203.1 [130.9] vs 168.4 [105.7] ng/mL). All AEs were assessed as mild or moderate and resolved without treatment, with the exception of elevated alanine aminotransferase and aspartate aminotransferase activities in one subject that resolved with treatment. Conclusions: The pharmacokinetics of glucuronidated genistein appeared to fit the linear-dose range of genistein 50 to 100 mg, but not the 300-mg dose in these healthy Chinese volunteers. Food consumption did not significantly affect the pharmacokinetic properties. No significant differences were observed in the pharmacokinetic parameters after multiple doses of genistein compared with a single dose, suggesting that the drug did not accumulate after multiple doses.

Pharmacokinetics of single-dose and multiple-dose memantine in healthy chinese volunteers using an analytic method of liquid chromatography-tandem mass spectrometry

Objective: This study consisted of 2 phases: development of a liquid chromatography-tandem mass spectrometry (LC/MS) method for determination of memantine in human plasma and characterization of single-dose and multiple-dose pharmacokinetic profiles of memantine in healthy Chinese volunteers using the LC/MS method. Methods: An analytic method of LC/MS for determination of memantine in human plasma was developed and validated and was applied to this singlecenter, open-label, single-dose and multiple-dose pharmacokinetic study conducted in healthy native Chinese volunteers. Subjects were randomized to receive a single dose of 5, 10, or 20 mg of memantine to study the linear characteristics of pharmacokinetics, or a multiple dose of 5 mg once daily for 14 days to study the drug accumulation. The pharmacokinetic parameters calculated included C max, T max, AUC, t 1/2,mean residence time (MRT), maximum steady-state plasma concentration (C ssmax), minimum steady-state plasma concentration ( ssmin), average steady-state plasma concentration (C ssav), and fluctuation percentage (DF). All values were expressed as mean (SD). Sequential blood samples were collected from 0 to 360 hours for single-dose pharmacokinetic determinations after the dose on day 1; in the multiple-dose pharmacokinetic arm, the sequential blood samples were also obtained from 0 to 360 hours on day 14 after collecting the predose samples at 0 hour on days 11, 12, and 13. Memantine concentrations in plasma were determined by LC/MS method. A calibration curve was constructed by 7 memantine concentrations and processed by least-squares linear regression analysis (w = 1/x 2). Safety assessments, including adverse events (AEs), were performed at all study visits. Results: The LC/MS method for determination of memantine in human plasma was developed and validated. The standard calibration curve for spiked human plasma containing memantine was linear in the concentration range of 0.2 to 200.0 ng/mL. The correlation coefficient was greater than 0.9960 (n = 6). The lower limit of quantification for memantine in human plasma was 0.2 ng/mL, and the intraday and interday coefficients of variation were all lower than 15%. The mean recoveries of the 0.4, 20.0, and 180.0 ng/mL levels were 78.87%, 81.55%, and 81.98%, respectively. The coefficients of variation were all lower than 15% after being treated at room temperature for 24 hours, for 45 days at -40°, and within 3 freeze-and-thaw cycles in plasma samples. Forty native Chinese subjects (10 [5 men, 5 women] subjects per group; mean [SD] age, 21.6 [1.6] [range, 19-27] years; weight, 63.0 [7.7] [range, 52-82] kg; height, 170.0 [7.0] [range, 155-185] cm) were enrolled in the study. After singledose oral administration, the main pharmacokinetic parameters found for memantine at doses of 5, 10, and 20 mg were as follows: C max, 6.20 (0.75), 11.60 (1.95), and 25.34 (8.34) ng/mL, respectively; T max, 5.70 (1.64), 6.00 (1.33), and 6.89 (1.41) h; AUC 0-t, 486.19 (80.00), 889.32 (239.49), and 1772.91 (784.07) ng · h/mL; AUC 0-∞, 540.05 (89.68), 932.07 (230.82), and 1853.29 (776.85) ng · h/mL; t 1/2, 66.86 (11.75), 63.57 (12.58), and 62.06 (9.26) h; and MRT, 99.37 (16.96), 91.73 (18.16), and 89.56 (13.77) h. The main pharmacokinetic parameters found for memantine at doses of 5 mg once daily for 14 days were as follows: T max, 6.80 (2.46) h; C ssmax, 19.69 (2.00) ng/mL; C ssmin, 12.76 (2.80) ng/mL; C ssav, 16.10 (2.46) ng/mL; t 1/2, 64.57 (15.78) h; MRT, 93.17 (23.38) h; AUC ss,386.37 (59.00) ng · h/mL; and DF, 44.47% (15.27%). One female subject withdrew from the study after a single 20-mg dose due to an AE (dizziness and vomiting); no other subjects experienced an AE. Conclusions: In these healthy Chinese subjects, the t 1/2 and MRT values were fixed and did not increase following the increased dose, and the AUC ∞ and C max values increased following the increasing dosage of memantine. Linear pharmacokinetics was found at doses from 5 to 20 mg. The multiple-dose pharmacokinetic parameters (other than C max) were nearly similar compared with the single-dose administration. The maximum plasma concentration of memantine after multiple-dose administration was greater than that after a single-dose administration, suggesting memantine accumulation with multiple-dose administration of 5 mg and requiring further confirmation in larger studies.

Single- and Multiple-Dose Pharmacokinetics and Tolerability of Gepirone Extended-Release

To determine the single- and multiple-dose pharmacokinetic profile of gepirone extended-release (ER) in healthy individuals. The single- and multiple-dose pharmacokinetics of gepirone-ER were investigated in three randomised, placebo-controlled studies of 115 healthy subjects. Dosages ranged from 10 to 75 mg/day for 6 days (study 1), 20 mg/day for 7 days (study 2), and 120 mg/day for 7 days (study 3). Blood samples were obtained to measure plasma levels of gepirone and the l-pyrimidinyl-(2-pipera-zine) [1-PP] metabolite prior to the first dose and other intervals on the first and last treatment days. Pharmacokinetic parameters included peak plasma level (Cmax), time to peak plasma level (tmax), and area under the concentration-time curve (AUC). In single-dose studies, peak gepirone-ER plasma concentrations were reached in approximately 4 to 5 hours and slowly declined over the next 20 hours. Steady-state plasma gepirone concentrations were reached by day 2 during multiple-dose studies; Cmax, minimum trough plasma concentration (Cmin) and AUC were dose proportional. Greater fluctuations in plasma concentrations were observed with gepirone solution than with gepirone-ER. The AUC for gepirone-ER was approximately 80% of that for gepirone solution. A similar pharmaco-kinetic profile was observed for the 1-PP metabolite. Gepirone-ER was generally well tolerated at all doses in all age groups except for 120 mg/day. The incidence of adverse events, including headache, dizziness and nausea, tended to be higher in gepirone-ER than in placebo recipients. Gepirone and 1-PP exhibited linear pharmacokinetic profiles. Peak/trough fluctuations in plasma gepirone concentrations were reduced by gepirone-ER, while total exposure to drug (AUC) was maintained. Overall, gepirone-ER was well tolerated. As a result of lower peak plasma levels, gepirone-ER may be expected to reduce the incidence of adverse events compared with gepirone immediate-release and thus has the potential to improve response.

Single-dose and multiple-dose pharmacokinetics of etintidine in healthy volunteers.

The present study was designed to determine the single- and multiple-dose pharmacokinetic profiles of the H2 receptor antagonist etintidine in healthy volunteers. Etintidine was rapidly absorbed and eliminated after the oral administration of 300 mg base equivalent of etintidine HCl in a capsule formulation to 11 healthy subjects. Comparison of the pharmacokinetics after a single dose and during steady state showed no significant differences (p greater than 0.05) in the mean values of Cmax, tmax, oral clearance, elimination rate constant, and renal clearance, indicating no significant accumulation of etintidine and no apparent time-dependent changes in the pharmacokinetics of etintidine during multiple dose administration.

Pharmacokinetics of isotretinoin during repetitive dosing to patients.

The multiple dose pharmacokinetics of isotretinoin and its major blood metabolite, 4-oxo-isotretinoin, were studied in 10 patients with cystic acne and 11 patients with various keratinization disorders. Blood samples were obtained at predetermined times following the first dose, interim doses and the final dose. Blood concentrations of isotretinoin and 4-oxo-isotretinoin were measured by a specific and sensitive HPLC method. A lag time was usually observed prior to the onset of absorption following oral administration of the drug in a soft elastic gelatin capsule. Absorption then proceeded rapidly and maximum blood concentrations usually occurred within 4 h of drug administration. The harmonic mean half-life for the elimination of isotretinoin by the cystic acne patients was approximately 10 h after the initial dose and did not change significantly following 25 days of 40 mg b.i.d. dosing. Steady-state blood concentrations remained relatively constant after the fifth day of dosing. The harmonic mean elimination half-life in the patients with various disorders of keratinization was about 16 h. The results of the 2 studies suggest that no significant changes in the pharmacokinetics of isotretinoin occur during multiple dosing and that the multiple dose pharmacokinetic profile is predictable and can be described using a linear pharmacokinetic model. This suggests that the steady-state concentrations of isotretinoin can be predicted from single dose data.

Reduced Single-dose Clearance of Clobazam in Elderly Men Predicts Increased Multiple-dose Accumulation1

The rate and extent of accumulation of clobazam and its major metabolite, desmethylclobazam, during multiple dosage with clobazam were evaluated in 4 similarly sized groups of young male, young female, elderly male, and elderly female volunteers. Subjects received single 10mg doses of clobazam daily for 22 consecutive days. Plasma levels were measured during and after the period of dosage. Compared with the young male subjects, elderly males had slower rates of clobazam accumulation and washout, higher steady-state plasma levels, and lower steady-state clearance. Accumulation of desmethylclobazam also was slower and more extensive in the elderly male group. Among females, however, age-related kinetic differences did not approach significance. Among all subjects, pharmacokinetic variables for clobazam determined in a previous single-dose study were highly consistent with the multiple-dose pharmacokinetic profile. Single-dose vs post-multiple dosage half-life, single-dose vs steady-state clearance, observed vs predicted accumulation ratios, and observed vs predicted steady-state plasma concentrations were all highly correlated, with regression line slopes close to unity. Thus, reduced single-dose clearance of clobazam in elderly men leads to slower and more extensive accumulation during multiple dosage. The single-dose pharmacokinetic profile of clobazam is highly predictive of drug behaviour during repeated dosage, suggesting that clobazam kinetics are dose- and concentration-independent within the range studied, and that self-induction or inhibition of clearance is not evident during 3 weeks of dosage.