Chulalongkorn Medical Journal


Background : Azithromycin is a broad spectrum azalide antibiotic which was suggested to be first-line treatment in children for some respiratory tract infections, urethritis and mycobacterium avium complex infection with AIDs complications. The drug is well absorbed and has long half-life which supports a short time administration at higher dose regimens. Pharmacokinetic and bioequivalence of azithromycin have been extensively studied in many oral dosage forms at the standard dose of 500 mg; however, there is no bioequivalence study at higher dose carried out in an oral suspension dosage form. Objective : To investigate bioequivalence of azithromycin powder for oral suspension with a single dose of 600 mg intended to be used as a high dose regimen for treatment of infectious diseases in children. Design : A two-way crossover design. Setting : Clinical study and drug assay were performed at Burachat Chaiyakorn Hospital, Bangkok and SGS Laboratory, Bangkok, respectively. Materials and Methods : Twenty-four healthy Thai volunteers participated in the study. The study design followed a two-way crossover design with two-treatment, two sequences and two periods with a 4-week washout period. The test product, Azith(Siam Bheasach, Thailand), was compared with a reference product, Zithromax (Pfizer, USA). Blood samples were collected for 168 h postdose and plasma drug concentrations were determined by LC-MS. An individual plasma concentration-time profile from each treatment was analyzed for relevant pharmacokinetic parameters and its bioequivalence was evaluated between both formulations. Results : The dose regimen was well tolerated in all volunteers. The drug was rapidly absorbed given tmax of 2-2.5 h for both products. The values of Cmax, AUC0-t and t1/2 were 560.81 ± 231.94 ng/mL, 4655.15 ± 2015.31 ng.h/mL and 35.82 ± 13.65 h for the test product and 556.80 ± 308.13 ng/mL, 4583.67 ± 2066.49 ng.h/mL and 34.14 ± 14.31 h for the reference product, respectively. The 90% confidence intervals for the ratios of the test product to the reference product were within the bioequivalence acceptation range of 80-125%. Conclusion : The result showed the bioequivalence between the test product and reference product in terms of both rate and extent of drug absorption after administration of a single oral dose of 600 mg azithromycin.



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