Saliva versus Plasma Relative Bioavailability of Tolterodine in Humans: Validation of Class III Drugs of the Salivary Excretion Classification System

Relative bioavailability study of tolterodine in healthy human volunteers was done using saliva and plasma matrices in order to investigate the robustness of using saliva instead of plasma as a surrogate for bioavailability and bioequivalence of class III drugs according to the salivary excretion classification system (SECS). Saliva and plasma samples were collected up to 16 h after 2 mg oral dose. Saliva and plasma pharmacokinetic parameters were calculated by non compartmental analysis using Kinetica program V5. Human effective intestinal permeability was optimized by SimCYP program V13. Tolterodine falls into class III (High permeability/Low fraction unbound to plasma proteins) and hence was subjected to salivary excretion. A high pearsons correlation coefficient of 0.97 between mean saliva and plasma concentrations, and saliva/plasma concentrations ratio of 0.33 were observed. In addition, correlation coefficients and saliva/plasma ratios of area under curve and maximum concentration were 0.98, 0.95 and 0.42, 0.34 respectively. On the other hand, time to reach maximum concentration was higher in saliva by 2.37 fold. In addition, inter subject variability values in saliva were slightly higher than plasma leading to need for slightly higher number of subjects to be used in saliva studies (55 vs. 48 subjects). Non-invasive saliva sampling instead of invasive plasma sampling method can be used as a surrogate for bioavailability and bioequivalence of SECS class I drugs when adequate sample size is used.

Saliva vs. plasma bioequivalence of metformin in humans: validation of class II drugs of the salivary excretion classification system

To study saliva and plasma bioequivalence of metformin in humans, and to investigate the robustness of using saliva instead of plasma as surrogate for bioequivalence of class II drugs according to the salivary excretion classification system (SECS).Plasma and saliva samples were collected for 12 h after 500 mg oral dosing of metformin to 16 healthy humans. Plasma and saliva pharmacokinetic parameters, 90% confidence intervals and intra-subject variability values were calculated using Kinetica V5. Descriptive statistics and dimensional analysis were calculated by Excel. SimCYP program V13 was used for estimation of effective intestinal permeability.Metformin was subjected to salivary excretion since it falls into class II (Low permeability/High fraction unbound to plasma proteins), with correlation coefficients of 0.95-0.99 between plasma and saliva concentrations. Saliva/plasma concentration ratios were 0.29-0.39. The 90% confidence limits of all parameters failed in both saliva and plasma. Intra-subject variability values in saliva were higher than plasma leading to need for higher number of subjects to be used in saliva.Saliva instead of plasma can be used as surrogate for bioequivalence of class II drugs according to SECS when adequate sample size is used. Future work is planned to demonstrate SECS robustness in drugs that fall into class III.

Bioequivalence of two pregabalin 300 mg capsules (Neurexal and Lyrica®) in healthy human volunteers

The pharmacokinetics of 2 brands of pregabalin 300 mg capsules were compared in 23 healthy human volunteers after a single oral dose in a randomized cross-over study. The study protocol was prepared with relevance to the requirements set in the US FDA and the EMA guidances for conduction of bioequivalence studies. Reference (Lyrica(®), Pfizer, France) and test (Neurexal, Pharmaline, Lebanon) products were administered to fasted volunteers. Blood samples were collected up to 48 h and assayed for pregabalin using a validated LC-MS/MS method. The pharmacokinetic parameters AUC0-t, AUC0-∞, Cmax, Tmax, T1/2 and elimination rate constant were determined from plasma concentration-time profile by non-compartmental analysis method using WinNonlin V5.2. The analysis of variance did not show any significant difference between the 2 formulations and 90% confidence intervals fell within the acceptable range for bioequivalence: 80-125%. It was concluded that the 2 brands exhibited comparable pharmacokinetic profiles and that Pharmaline's Neurexal is bioequivalent to Lyrica(®) of Pfizer, France.

Bioequivalence assessment of Azomycin (Julphar, UAE) as compared to Zithromax (Pfizer, USA)--two brands of azithromycin--in healthy human volunteers

Two studies have been performed to assess the relative bioavailability of Azomycin (Julphar, UAE) as compared with Zithromax (Pfizer, USA) at the International Pharmaceutical Research Center (IPRC), Amman, Jordan. One study involved Azomycin capsules and the other Azomycin suspension. Each study enrolled 24 volunteers and in both studies, after an overnight fasting, the two brands of azithromycin were administered as single dose on two treatment days separated by a 2 weeks washout period. After dosing, serial blood samples were collected for a period of 192 h. Plasma harvested from blood, was analysed for azithromycin by HPLC coupled with electrochemical detection. Various pharmacokinetic parameters including AUC(0-t,) AUC(0-infinity,) C(max), T(max), T(1/2) and K(elm) were determined from plasma concentrations for both formulations and found to be in good agreement with the reported values. AUC(0-t), AUC(0-infinity) and C(max) were tested for bioequivalence after log-transformation of data. No significant difference was found based on ANOVA; 90% confidence intervals for the test/reference ratios of these parameters were found within the bioequivalence acceptance range of 80-125%. Based on these statistical inferences it was concluded that Azomycin capsule is bioequivalent to Zithromax capsule and Azomycin suspension is bioequivalent to Zithromax suspension.