ABSTRACT
Primaquine is rapidly and completely absorbed with an absolute oral bioavailability of around 96% (5). Peak plasma levels of 150-200 ng/ml are reached within 2-3 hours after a 45 mg dose. It is extensively distributed into body tissue with a volume of distribution of around 3-4 l/kg (5-8). Primaquine is a low clearance drug (24.2±7.4 l/h) and is mainly eliminated by metabolism. According to one study using 14C-primaquine, the total radioactivity in the plasma declined slowly and was still significant after 4 days. Primaquine itself was almost completely eliminated during the first 24 hours, with a plasma half-life of around 7 hours (5). Only 1% of an oral dose was excreted unchanged through the kidneys over 24 hours (6-8). One major metabolite, carboxyprimaquine, has been identified in human blood (7) and another, 6-methoxyprimaquine, in the urine in small amounts (2). Carboxyprimaquine accumulates in the plasma to much higher concentrations than that of the parent compound because of its slow elimination from the body (5, 9).
