Chulalongkorn Medical Journal


Background : Azithromycin is a broad spectrum azalide antibiotic which wassuggested to be first-line treatment in children for somerespiratory tract infections, urethritis and mycobacterium aviumcomplex infection with AIDs complications. The drug is wellabsorbed and has long half-life which supports a short timeadministration at higher dose regimens. Pharmacokinetic andbioequivalence of azithromycin have been extensively studiedin many oral dosage forms at the standard dose of 500 mg;however, there is no bioequivalence study at higher dose carriedout in an oral suspension dosage form.Objective : To investigate bioequivalence of azithromycin powder for oralsuspension with a single dose of 600 mg intended to be usedas a high dose regimen for treatment of infectious diseases inchildren.Design : A two-way crossover design.Setting : Clinical study and drug assay were performed at BurachatChaiyakorn 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 withtwo-treatment, two sequences and two periods with a 4-weekwashout period. The test product, Azith(Siam Bheasach,Thailand), was compared with a reference product, Zithromax(Pfizer, USA). Blood samples were collected for 168 h postdoseand plasma drug concentrations were determined byLC-MS. An individual plasma concentration-time profile fromeach treatment was analyzed for relevant pharmacokineticparameters and its bioequivalence was evaluated between bothformulations.Results : The dose regimen was well tolerated in all volunteers. The drugwas 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 testproduct and 556.80 ± 308.13 ng/mL, 4583.67 ± 2066.49ng.h/mL and 34.14 ± 14.31 h for the reference product,respectively. The 90% confidence intervals for the ratios ofthe test product to the reference product were within thebioequivalence acceptation range of 80-125%.Conclusion : The result showed the bioequivalence between the test productand reference product in terms of both rate and extent of drugabsorption after administration of a single oral dose of 600 mgazithromycin.


Faculty of Medicine, Chulalongkorn University

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