METHOD: The effects of organic modifiers in mobile phase, protein precipitation agent to plasma sample ratio, and light on montelukast stability in unprocessed and processed human plasma, were evaluated. Validation was conducted in accordance with European Medicines Agency Guideline on bioanalytical method validation.

RESULTS: No interference peak was observed when acetonitrile was used as an organic modifier. Acetonitrile to plasma ratio of 4:1 produced clean plasma sample. Approximately 3 % of cis isomer was detected in unprocessed plasma samples while 21 % of cis isomer was detected in processed plasma samples after exposing to fluorescent light for 24h. The standard calibration curve was linear over 3.00-1200.00 ng/mL. All method validation parameters were within the acceptance criteria.

SETTING: A sample of 1419 Malaysian community pharmacies with resident pharmacists.

METHOD: A cross-sectional nationwide survey using a self-completed mailing questionnaire.

MAIN OUTCOME MEASURE: Pharmacists' views on generic medicines including issues surrounding efficacy, safety, quality and bioequivalence.

RESULTS: Responses were received from 219 pharmacies (response rate 15.4%). Only 50.2% of the surveyed pharmacists agreed that all products that are approved as generic equivalents can be considered therapeutically equivalent with the innovator medicines. Around 76% of respondents indicated that generic substitution of narrow therapeutic index medicines is inappropriate. The majority of the pharmacists understood that a generic medicine must contain the same amount of active ingredient (84.5%) and must be in the same dosage form as the innovator brand (71.7%). About 21% of respondents though that generic medicines are of inferior quality compared to innovator medicines. Most of the pharmacists (61.6%) disagreed that generic medicines produce more side-effects than innovator brand. Pharmacists graduated from Malaysian universities, twinning program and overseas universities were not differed significantly in their views on generic medicines. Additionally, the respondents appeared to have difficulty in ascertaining the bioequivalent status of the marketed generic products in Malaysia.

METHOD: This is a single-center, single-dose, open-label, randomized, 2-treatment, 2-sequence and 2-period crossover study with a washout period of 7 days. Paracetamol/Orphenadrine tablets were administered after a 10-h fast. Blood samples for pharmacokinetic analysis were collected at scheduled time intervals prior to and up to 72 h after dosing. Blood samples were centrifuged, and separated plasma were kept frozen (- 15 °C to - 25 °C) until analysis. Plasma concentrations of orphenadrine and paracetamol were quantified using liquid-chromatography-tandem mass spectrometer using diphenhydramine as internal standard. The pharmacokinetic parameters AUC0-∞, AUC0-t and Cmax were determined using plasma concentration time profile for both preparations. Bioequivalence was assessed according to the ASEAN guideline acceptance criteria for bioequivalence which is the 90% confidence intervals of AUC0-∞, AUC0-t and Cmax ratio must be within the range of 80.00-125.00%.

RESULTS: There were 28 healthy subjects enrolled, and 27 subjects completed this trial. There were no significant differences observed between the AUC0-∞, AUC0-t and Cmax of both test and reference preparations in fasted condition. The 90% confidence intervals for the ratio of AUC0-t (100.92-111.27%), AUC0-∞ (96.94-108.08%) and Cmax (100.11-112.50%) for orphenadrine (n = 25); and AUC0-t (94.29-101.83%), AUC0-∞ (94.77-101.68%) and Cmax (87.12-101.20%) for paracetamol (n = 27) for test preparation over reference preparation were all within acceptable bioequivalence range of 80.00-125.00%.

CONCLUSION: The test preparation is bioequivalent to the reference preparation and can be used interchangeably.