The treatment and prophylaxis of malaria

A comparative study of the efficacies of chloroquine and a pyrimethamine-dapsone combination in clearing Plasmodium falciparum parasitaemia in school children in Tanzania

A randomized study on the in vivo efficacies of chloroquine and a pyrimethamine-dapsone combination (Maloprim) in clearing P. falciparum parasitaemia was carried out in 77 asymptomatic semi-immune schoolchildren in the Kilombero District of Tanzania. Children were randomized to receive either chloroquine at a dose of 25 mg/kg over three days, or Maloprim (6.25 mg pyrimethamine + 50 mg dapsone for children under 10 years, and 12.5 mg pyrimethamine + 100 mg dapsone for children 10 or more years old) as a single dose. Children were followed-up for malaria parasitaemia at days 2, 7 and 14 after screening, randomization and treatment. The slide positivity rate was lower in the Maloprim group at all cross-sectional surveys (23 vs 37% at day 2; 9 vs 20% at day 7; 21 vs 32% at day 14) but none of these differences reached statistical significance. No cases in the Maloprim group showed RII resistance, whereas in the chloroquine group, 2 cases showed RII resistance and a further 2 cases RIII resistance (6%). No major side-effects were reported. The combination of pyrimethamine-dapsone appears to be a better choice than chloroquine as a chemoprophylactic regimen for malaria in this area. Although they need to be confirmed in a larger study, these results may be of interest to the policy-makers as well as researchers.

[Mefloquine chemoprophylaxis of malaria in the Brazilian Amazonia]

In a randomised double-blind study 122 volunteers living in an endemic malarious area in Amazonian Rondônia state were divided into 4 groups to study malaria suppression. . The first group received 500 mg of mefloquine every month, group II 250 mg every two weeks, group III a tablet of Fansidar (500 mg sulphadoxine + 25mg pyrimethamine) a week and group IV placebo. Acute attacks of malaria occurred in one individual in group I, 2 subject in group II, and 6 individuals in groups III and IV. Protection with mefloquine was significant compared with the placebo group. Both treatment regimens with mefloquine were effective suppressants in an area of high prevalence of drug multiresistant Plasmodium falciparum transmission.

Imported malaria in Australia

OBJECTIVE

To obtain information on imported malaria in Australia.

DESIGN AND SETTING

Patients with malaria diagnosed by microscopy by laboratories in southeast Queensland and northern New South Wales between October 1987 and December 1988 were included in this study. The chi 2 test was used to analyse data.

PATIENTS

Blood films, details of prophylactic regimens and clinical history were received from 146 patients.

MAIN OUTCOME MEASURES

This study was to determine the percentage of patients infected with each malaria species, where they contracted their infections, whether they had taken appropriate prophylactic agents and to determine the relationship between parasitaemia and previous exposure, symptoms and prophylaxis.

RESULTS

One hundred patients (68.5%) had Plasmodium vivax malaria and 33 patients (22.6%) had Plasmodium falciparum malaria, with 3 (2.1%) infected with both of these malaria species. Ten cases (6.8%) were presumptively diagnosed as infections but diagnosis by microscopy was uncertain. Seventy-four per cent of the P. vivax infections and 85% of the P. falciparum infections were contracted in Papua New Guinea. Patients presented with a range of blood parasite concentrations that did not correlate with their symptoms, previous infection with malaria (P greater than 0.25) or the regular taking of prophylactic drugs (P greater than 0.1). Only 41% of the patients took any prophylactic drugs; the figure for temporary visitors to malarious areas was 54%. Only 11.6% of patients were taking the recommended drugs for the malarious areas they visited or were resident in.

CONCLUSIONS

Constant monitoring of malarial infections is needed to ensure that appropriate advice is given to the traveller. Our study supports the dogma that malaria should be suspected in all patients who have been to malarious areas, regardless of previous malarious attacks, prophylaxis, treatment or the time which has elapsed since leaving the area.

Pharmacokinetics of halofantrine in man: effects of food and dose size

1. Plasma concentrations of halofantrine (Hf) and its putative principal plasma metabolite desbutyl halofantrine (Hfm) have been measured in two separate studies after oral administration of the hydrochloride salt. 2. Six healthy male volunteers each received single oral doses of 250, 500 and 1000 mg administered after an overnight fast. A washout period of at least 6 weeks was allowed between each dose. A further 250 mg single oral dose was administered to the same six subjects in a fasting state and after a standardised fatty meal in a randomised study, again with a washout period of at least 6 weeks. 3. AUC and maximum plasma concentration (Cmax) for Hf increased in proportion to the dose from 250-500 mg. This increase was non-proportional when the dose was increased from 500 to 1000 mg. For Hfm, in the dose range 250-500 mg, AUC but not Cmax increased in proportion in the increase in dose size. The increase in these parameters was non-proportional when the dose was increased from 500 to 1000 mg. Time to reach peak concentrations for Hf and Hfm and the elimination half-life of Hf remained unchanged across the dosage range. 4. Following a fatty meal, Cmax for Hf was increased from 184 +/- 115 micrograms l-1 (fasting) to 1218 +/- 464 micrograms l-1 (fed). AUC for Hf was increased from 3.9 +/- 2.6 mg l-1 h (fasting) to 11.3 +/- 3.5 mg l-1 h following a fatty meal.(ABSTRACT TRUNCATED AT 250 WORDS)

Malaria--an overview

The epidemiology, clinical features, diagnosis, prognosis, management, chemotherapy and chemoprophylaxis of malaria are reviewed.

Efficacy of multiple-dose halofantrine in treatment of chloroquine-resistant falciparum malaria in children in Kenya

Halofantrine hydrochloride given to 46 Kenyan children with falciparum malaria at 10 mg/kg for two doses, and to 60 other children at 8 mg/kg for three doses, resulted in rapid parasite clearance, mean parasite clearance times being 45.4 h and 54.8 h, respectively. In-vitro chemosensitivity tests showed that most infections were due to chloroquine-resistant parasites, and that parasite maturation was inhibited by considerably lower concentrations of halofantrine than of chloroquine.

Clinical trials with halofantrine hydrochloride in Malawi

Two clinical trials of the phenanthrene methanol compound halofantrine in the treatment of Plasmodium falciparum were conducted in Malawi, in areas where the parasite was known to be chloroquine resistant. In the first trial all 46 patients had symptoms of malaria and parasite densities ranging from 2500/microliter to 212,000/microliter. They were given a single dose of halofantrine hydrochloride, 16 mg/kg body weight. The recrudescence rate on day 14 of follow up was unacceptably high (38%). In the second trial the dose given was 8 mg/kg 6 hourly for three doses. Of the 49 children followed up for 14 days, 47 became aparasitaemic--ie, the cure rate was 96%. In both trials the drug was very well tolerated. Halofantrine hydrochloride seems to be effective against P falciparum chloroquine sensitive and resistant strains in Africa.