CNS adverse events associated with antimalarial agents. Fact or fiction?

Malaria

The preeminent infectious threat to unwary tropical travelers, malaria is a preventable, mosquito-borne protozoan infection of red blood cells, which causes fever, anemia, respiratory failure, coma, and death. Malaria is a true medical emergency that requires rapid diagnosis and treatment. Unfortunately, in two thirds of tropical travelers who die of malaria, either treatment is delayed or the diagnosis is simply missed. Every tropical traveler with fever or unexplained, flu-like illness must be assumed to have life-threatening malaria and must have thick and thin blood smears immediately examined to confirm the diagnosis.

Mefloquine in infants and young children

In an area where multi-drug resistance in Plasmodium falciparum is a particular problem, more than 500 children under 5 years of age weighing > 5 kg were treated with mefloquine, either alone or combined with an artemisinin derivative, and followed up for a minimum of 28 days. The principal adverse effect was vomiting and this was associated with reduced efficacy of treatment (even when treatment was repeated). Later adverse effects occurred less frequently than in adults. There was no serious toxicity and, in particular, there were no neuropsychiatric side-effects. The high dose of mefloquine (25 mg/kg) required in this area is well tolerated by young children. It should be given in a divided dose of 15 mg/kg initially, followed by 10 mg/kg > or = 12 hours later.

Post-malaria neurological syndrome

BACKGROUND

Neurological signs and symptoms are common in malaria, but observations in Vietnam and Thailand have pointed to a discrete transient neurological syndrome after recovery from severe infections.

METHODS

A prospective study of the post-malaria neurological syndrome (PMNS) was conducted at two centres in Vietnam over four years. Criteria for inclusion were recent symptomatic malaria infection with parasites cleared from blood (and in cases of cerebral malaria full recovery of consciousness), and development of neurological or psychiatric symptoms within two months after the acute illness. Half of the patients with severe falciparum malaria had been taking part in a randomised trial of antimalarials.

FINDINGS

Of 18,124 patients with falciparum malaria treated (1176 of whom had severe infections) 19 adults and three children had subsequent PMNS; in one patient it followed uncomplicated malaria and in 21 it followed severe malaria. The overall incidence (95% confidence interval) of PMNS after falciparum malaria at the main study centre was 1.2 per 1000 (0.7 to 1.8 per 1000) and relative risk (95% CI) for developing PMNS after severe versus uncomplicated falciparum malaria was 299 (40 to 2223). 13 patients had an acute confusional state or psychosis, six had one or more generalised convulsions, two had generalised convulsions followed by a long period of acute confusion, and one developed a fine tremor. At the time of PMNS diagnosis all patients were aparasitaemic. The syndrome was self-limiting, median duration 60 h (range 24-240). PMNS was associated with the use of oral mefloquine. In the randomised trial 4.4% (10/228) of patients with severe malaria who received mefloquine after parenteral treatment developed PMNS compared with 0.5% (1/210) of those who received quinine; relative risk 9.2 (95% CI 1.2 to 71.3, p = 0.012).

INTERPRETATION

Mefloquine is not the only risk factor for PMNS but it is a strong one. Where an effective alternative drug is available, mefloquine should not be used after treatment of severe malaria.