Unexpected frequency, duration and spectrum of adverse events after therapeutic dose of mefloquine in healthy adults.

The frequency and spectrum of adverse events associated with the antimalarial therapeutic regimen of mefloquine (MQ) (750 and 500 mg at an interval of 6 h) was assessed in 22 healthy volunteers who were monitored for 21 days following drug administration. An unexpected high frequency of side effects of any grade were reported by all 22 subjects. The most commonly reported symptoms were vertigo (96%), followed by nausea (82%) and headache (73%). Participants suffering from severe (grade 3) vertigo (73%) required bed rest and specific medication for 1 to 4 days. More females than males reported severe adverse reactions. The majority (77.3%) of the participants (f: 8/12, m: 9/10) showed symptom resolution within 3 weeks (510 h) after drug administration. Biochemical and haematological findings stayed within the normal range of values, but showed nevertheless a significant rise of Na, Cl, Ca, bilirubin, GGT and LDH. The unexpectedly high frequency and severity of adverse reactions after normal therapeutic dosage of MQ in healthy subjects may influence future recommendations regarding the use of MQ for stand-by treatment of suspected malaria in travellers.