Quinine pharmacokinetics: ototoxic and cardiotoxic effects in healthy Caucasian subjects and in patients with falciparum malaria

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Abstract
To study the pharmacokinetic behaviour of quinine in Caucasians with and without malaria. Quinine-dihydrochloride was administered intravenously as a single dose of 300 mg to 12 healthy subjects and as multiple doses of 600 mg in 4 h every 8 h in 10 patients with falciparum malaria. Plasma quinine concentrations were measured by high-performance liquid chromatography Quinine pharmacokinetics are time-dependent: the apparent elimination halftime is shorter in the accumulation phase than in the elimination phase; in malaria patients the maximal quinine concentration was reached in half the time calculated on the basis of the elimination phase after the last quinine infusion. Nevertheless a loading dose seemed advisable to reach adequate therapeutic levels quickly. In malaria patients the highest plasma concentrations during or at the end of the infusions were positively correlated with body weight. There was no correlation between body weight and the volume of distribution of quinine as calculated during the elimination phase. Hearing loss was audiometrically documented in 9 healthy subjects at a mean maximal plasma quinine concentration of only 2 mg/l. All malaria patients suffered serious cochlear hearing impairment. The ototoxic effects in both healthy subjects and patients appeared to be reversible. No electrographic changes were noted in the healthy subjects, whereas a clinically insignificant mean lengthening of the corrected QT interval was seen in the malaria patients. Intravenous quinine pharmacokinetics in healthy Caucasians were similar to those reported for Nigerian or Thai subjects. At effective doses quinine causes considerable but reversible cochlear hearing losses in both healthy persons and in patients. Our findings do support the need for a loading dose. The fact that in malaria patients there was no correlation between body weight and quinine VD as calculated during the elimination phase renders questionable the usefulness of dosing quinine according to body weight.