Objective: Routine malaria prophylaxis with chloroquine (CQ) is recommended to pregnant semi-immune women in several countries in Africa. The dosage is empirically based. We investigated whether blood CQ concentrations and apparent oral blood clearance (CL/F) change during the course of pregnancy. We also studied whether malaria parasites could be detected together with low CQ blood levels.
Methods: Forty nine semi-immune Tanzanian women were recruited in the 16th week of pregnancy. They were given 310 mg oral CQ base once per week as prophylaxis during the whole pregnancy. Capillary blood samples were taken for analysis of CQ before treatment and at weeks 26 and 36. Blood samples were dried on filter paper and analysed by HPLC. Blood was also drawn to detect occurrence of malaria parasites.
Results: A total of 25 women fulfilled the sampling schedule. CL/F increased significantly from 160 ml.min-1 at week 26 to 180 ml.min-1 at week 36. In 7 of 25 women, CL/F increased > 20%. Trough blood CQ concentrations, determined on four occasions at week 26 and at week 36 varied between 200 and 900 nmol.l-1. No statistically significant differences between occasions were seen. Malaria parasites were seen in two individuals early in pregnancy.
Conclusion: Blood CQ CL/F showed a small increase during the course of pregnancy. The estimated mean blood CL/F values of 160 and 180 ml.min-1 (week 26 and 36, respectively) were higher than the mean CL/F of 125 ml.min-1 in non-pregnant individuals, published previously. Efficacy of higher dosages of CQ in malaria prophylaxis in pregnant women could, therefore, be evaluated in controlled trials in high-risk malaria areas.