Effects of cigarette smoking on quinine pharmacokinetics in malaria

Effects of Plasmodium falciparum infection on the pharmacokinetics of quinine and its metabolites in pregnant and non-pregnant Sudanese women

PURPOSE

The study aimed to investigate the effects of Plasmodium falciparum infection on the pharmacokinetics of quinine and its metabolites in pregnant and non-pregnant Sudanese women.

METHODS

In a case-control study, nine pregnant and eight non-pregnant Sudanese women infected with P. falciparum were treated with intramuscular artemether. Before being given artemether, they received a single dose of quinine hydrochloride as intravenous infusion. Blood samples were collected frequently and analysed for quinine and its metabolites (phase I). One week later (after clearance of parasitaemia) the quinine part of the protocol was repeated (phase II).

RESULTS

During phase I, the AUCs (mean ± SD) of quinine and its major metaboplite, 3-hydroxyquinine, in pregnant women were 428.2 ± 132.4 and 27.8 ± 14.1 μmol l(-1) h(-1) respectively. In non-pregnant women the AUCs of quinine and 3-hydroxyquinine were 517.8 ± 100.0 and 32.3 ± 15.3 μmol l(-1) h(-1). In pregnant women the mean (90% confidence interval) AUC ratios of phase I to phase II of quinine and 3-hydroxyquinine were 1.6 (0.61, 4.22) and 1.01 (0.18, 5.60). In non-pregnant women, the AUC ratios of phase I to phase II of quinine and 3-hydroxyquinine were 1.93 (1.74, 2.15) and 1.19 (0.95, 1.47).

CONCLUSIONS

Plasmodium falciparum infection significantly increased plasma concentration of quinine in non-pregnant women and showed the same trend in pregnant women.

Quinine pharmacokinetic-pharmacodynamic relationships in uncomplicated falciparum malaria

The relationships between the pharmacokinetic properties of quinine during a 7-day treatment course and the therapeutic response were studied in 30 adult patients with uncomplicated falciparum malaria monitored for > or = 28 days. All patients received a 7-day oral quinine regimen either alone (n = 22) or in combination with rifampin (n = 8). The median fever clearance time was 58.5 h, and the mean +/- standard deviation parasite clearance time was 73 +/- 24 h. After recovery, six patients had recrudescences of Plasmodium falciparum malaria and seven had delayed appearances of P. vivax infection between days 16 and 23. Between the patients with and without recrudescences, there were no significant differences either in fever clearance time or parasite clearance time or in the overall pharmacokinetics of quinine and 3-hydroxyquinine. Patients for whom the area under the concentration-time curve from 3 to 7 days for quinine in plasma was <20 microg.day/ml had a relative risk of 5.3 (95% confidence interval = 1.6 to 17.7) of having a subsequent recrudescence of infection (P = 0.016). Modeling of these data suggested an average minimum parasiticidal concentration of quinine in plasma of 3.4 microg/ml and an MIC of 0.7 microg/ml for uncomplicated falciparum malaria in Thailand. To ensure a cure, the minimum parasiticidal concentration must be exceeded during four asexual cycles (>6 days).