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Pharmacokinetic interactions between chloroquine, sulfadoxine and pyrimethamine and their bioequivalence in a generic fixed-dose combination in healthy volunteers in Uganda


C Obua
M Ntale
MS Lundblad
M Mahindi
LL Gustafsson
JW Ogwal-Okeng
WW Anokbonggo
U Hellgren

Abstract

Background: A pre-packaged fixed-dose formulation of chloroquine (CQ) and sulfadoxine/pyrimethamine (S/P) combination (Homapak) is widely used for the treatment of falciparum malaria in Ugandan children. It is however a product whose pharmacokinetics and interactions have not been studied.

Objectives: To explore possible pharmacokinetic interactions between CQ and S/P during co-administration, and to determine their bioavailability in the locally made Homapak compared to the Good Manufacturing Practice (GMP) made formulations.

Methods: Thirty-two adult healthy volunteers were randomized into four groups and given single oral doses of fixed-dose CQ+S/P combination (Homapak), or GMP formulations of S/P (Fansidar), CQ (Pharco), or their combination. Plasma samples were followed for 21 days, analysed by HPLC-UV methods, with pharmacokinetic modeling using the WinNonlin software.

Results: Sulfadoxine in Homapak was more rapidly absorbed (ka = 0.55 h-1) than in Fansidar + CQ (ka = 0.27 h-1, p=0.004), but not more than S in Fansidar alone group (ka = 0.32 h-1, p=0.03). No significant differences were observed in the other pharmacokinetic parameters of S, P and CQ when given together or separately. The relative bioavailability of CQ and S in Homapak showed bioequivalence to reference formulations.

Conclusions: There were no pharmacokinetic interactions between CQ, S and P when the compounds were given together, however, more investigations would be needed to explore this further. Compared with GMP made drugs, both S and CQ are bioequivalent in Homapak, the Ugandan made fixed-dose formulation. Furthermore, the absorption of S was more rapid which could be advantageous in malaria treatment.

Keywords: sulfadoxine, pyrimethamine, chloroquine, bioequivalence, pharmacokinetic interactions

African Health Sciences Vol. 6(2) 2006: 86-92

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eISSN: 1729-0503
print ISSN: 1680-6905