Prediction of the human in vivo antiplatelet effect of S- and R-indobufen using population pharmacodynamic modeling and simulation based on in vitro platelet aggregation test

Indobufen (Ibustrin®), a reversible inhibitor of platelet aggregation, exists in two enantiomeric forms in 1:1 ratio. Here, we characterized the anti-platelet effect of S- and R-indobufen using response surface modeling using NONMEM® and predicted the therapeutic doses exerting the maximal efficacy of each enantioselective S- and R-indobufen formulation. S- and R-indobufen were added individually or together to 24 plasma samples from drug-naïve healthy subjects, generating 892 samples containing randomly selected concentrations of the drugs of 0–128 mg/L. Collagen-induced platelet aggregation in platelet-rich plasma was determined using a Chrono-log Lumi-Aggregometer. Inhibitory sigmoid I(max) model adequately described the anti-platelet effect. The S-form was more potent, whereas the R-form showed less inter-individual variation. No significant interaction was observed between the two enantiomers. The anti-platelet effect of multiple treatments with 200 mg indobufen twice daily doses was predicted in the simulation study, and the effect of S- or R-indobufen alone at various doses was predicted to define optimal dosing regimen for each enantiomer. Simulation study predicted that 200 mg twice daily administration of S-indobufen alone will produce more treatment effect than S-and R-mixture formulation. S-indobufen produced treatment effect at lower concentration than R-indobufen. However, inter-individual variation of the pharmacodynamic response was smaller in R-indobufen. The present study suggests the optimal doses of R-and S-enantioselective indobufen formulations in terms of treatment efficacy for patients with thromboembolic problems. The proposed methodology in this study can be applied to the develop novel enantio-selective drugs more efficiently.

Pharmacokinetic Characteristics of Ibandronate and Tolerability of DP-R206 (150 mg Ibandronate/24,000 IU Vitamin D3) Compared to the Ibandronate (150 mg) Monotherapy in Healthy Adults

Ibandronate (a bisphosphonate) is commonly used as an treatment of osteoporosis in combination with vitamin D. Monthly DP-R206-a novel, fixed-dose combination tablet (150 mg ibandronate/24,000 IU vitamin D3)-was recently developed to enhance patient compliance. This open, randomized, two-period crossover study was conducted to compare the pharmacokinetics of ibandronate when administered as DP-R206 or 150 mg ibandronate to healthy adult volunteers. Each volunteer was randomly allocated to receive single-dose DP-R206 or ibandronate with a 28-day washout period between treatments. Blood samples were assessed using pharmacokinetic analysis. Plasma ibandronate concentrations were determined using liquid chromatography-tandem mass spectrometry. Safety and tolerability assessments were performed throughout the study. In total, 103 participants received the study drugs and 72 participants completed the study. The geometric mean ratios (DP-R206/ibandronate) of the maximum concentration (C(max)) and the area under the plasma concentration time curve from time zero to the last concentration (AUC(last)) values were 0.959 (90% CI: 0.820-1.120) and 0.924 (90% CI: 0.805-1.060), respectively. The frequencies of adverse events (AEs) and drug reactions were similar between treatment groups, and all AEs were recovered without sequalae. Ibandronate pharmacokinetics, tolerability, and safety are comparable when administered to healthy individuals, regardless if administered as DP-R206 or ibandronate.

Bioequivalence of HCP1104, a New Fixed Dose Combination Drug and Co-administration of Eperisone 50 mg and Aceclofenac 100 mg: A Partial Replicated Crossover Study Design to Estimate the Pharmacokinetics of Highly Variable Drugs

BACKGROUND: This clinical study was conducted to compare pharmacokinetics of eperisone and aceclofenac of HCP1104, a new fixed dose combination drug with those in co-administration of eperisone 50 mg and aceclofenac 100 mg. The study used a partial replicated study design to characterize intra-subject variability of eperisone when co-administrated with aceclofenac. METHODS: A partial replicated crossover design was employed in 30 subjects. Each subject received a single dose of co-administration of eperisone 50 mg and aceclofenac 100 mg on two occasions and a single dose of 1 capsule of HCP1104. Blood samples were obtained for 24 hrs after dosing, and plasma was assayed for eperisone and aceclofenac by Liquid chromatography-electrospray ionization-mass spectrometry. RESULTS: Using an average bioequivalence criterion, the 90 % confidence limits for Ln-transformed Cmax and AUClast for aceclofenac fell wihin the acceptable range of 80 - 125 %. Point estimates of eperisone AUClast and Cmax were 1.0152 and 1.0490, respectively and the 90 % confidence interval for Cmax was 0.8499 - 1.3025. The within-subject coefficient of variation of Cmax for the reference was 50.198 %. Acceptance range for eperisone Cmax based on new bioequivalence guidance for highly variable drugs was extended to 0.6984 - 1.4319. CONCLUSION: The extent of exposure and rate of absorption of both eperisone and aceclofenac with a single dose of HCP1104 capsule were equivalent to those with co-administration of a marketed eperisone 50 mg tablet and a marketed aceclofenac 100 mg tablet under fasting conditions in healthy adult males.

Comparison of Pharmacokinetics and Safety of Two Formulations of Letrozole (2.5 mg) in Healthy Male Volunteers

BACKGROUND: Letrozole is an oral non-steroidal inhibitor of the aromatase enzyme, which has proven to be a useful drug against breast cancer. METHODS: This single-dose, randomized 2 x 2 crossover study was conducted in healthy male volunteers. Participants of each sequence group (each 13 volunteers for sequence group) received, in randomized sequence, a single oral 2.5-mg dose of generic letrozole (test) or branded letrozole (reference). Each treatment period was separated by a 5-week washout period. Blood samples were collected for up to 312 hours after drug administration, and drug concentrations were determined using validated LC/MS-MS. Pharmacokinetic properties were obtained using noncompartmental analysis. Drug tolerability was assessed throughout the study, using measurements of vital signs, physical examination, clinical chemistry testing, EKG, and interviews. RESULTS: A total of 26 subjects completed the study. The geometric mean ratios (90% CI) of Cmax and AUClast were 0.92 (0.85 - 0.99) and 1.01 (0.97 - 1.04), respectively. No serious AEs were reported, and there were no clinically significant differences between test and reference groups. CONCLUSION: The findings from this study suggest bioequivalence between two formulations of letrozole in healthy male volunteers. The safety profile of two formulations had similar characteristics.