RI quinine-Fansidar resistant falciparum malaria from Malawi

Novel 4-aminoquinoline analogs highly active against the blood and sexual stages of Plasmodium in vivo and in vitro

New drugs to treat malaria must act rapidly and be highly potent against asexual blood stages, well tolerated, and affordable to residents of regions of endemicity. This was the case with chloroquine (CQ), a 4-aminoquinoline drug used for the prevention and treatment of malaria. However, since the 1960s, Plasmodium falciparum resistance to this drug has spread globally, and more recently, emerging resistance to CQ by Plasmodium vivax threatens the health of 70 to 320 million people annually. Despite the emergence of CQ resistance, synthetic quinoline derivatives remain validated leads for new drug discovery, especially if they are effective against CQ-resistant strains of malaria. In this study, we investigated the activities of two novel 4-aminoquinoline derivatives, TDR 58845, N(1)-(7-chloro-quinolin-4-yl)-2-methyl-propane-1,2-diamine, and TDR 58846, N(1)-(7-chloro-quinolin-4-yl)-2,N(2),N(2)-trimethylpropane-1,2-diamine and found them to be active against P. falciparum in vitro and Plasmodium berghei in vivo. The P. falciparum clones and isolates tested were susceptible to TDR 58845 and TDR 58846 (50% inhibitory concentrations [IC(50)s] ranging from 5.52 to 89.8 nM), including the CQ-resistant reference clone W2 and two multidrug-resistant parasites recently isolated from Thailand and Cambodia. Moreover, these 4-aminoquinolines were active against early and late P. falciparum gametocyte stages and cured BALB/c mice infected with P. berghei. TDR 58845 and TDR 58846 at 40 mg/kg were sufficient to cure mice, and total doses of 480 mg/kg of body weight were well tolerated. Our findings suggest these novel 4-aminoquinolines should be considered for development as potent antimalarials that can be used in combination to treat multidrug-resistant P. falciparum and P. vivax.

The metabolic effects of quinine in children with severe and complicated Plasmodium falciparum malaria in Dar es Salaam

Quinine is widely used for the treatment of severe and complicated malaria, although resistant strains of Plasmodium falciparum may occur. The drug has been incriminated as a cause of hypoglycaemia in some malaria patients. To determine if quinine has untoward metabolic effects during treatment of severe and complicated malaria we have studied the effects of quinine on blood glucose and intermediary metabolites, serum insulin, C-peptide, plasma glucagon and non-esterified fatty acids in 97 children with severe malaria in Dar es Salaam. All patients responded clinically. No patient developed hypoglycaemia while on quinine therapy given as 10 mg/kg in 10 ml/kg of 5% dextrose infused over 4 h every 8 h. Endogenous insulin secretion, as reflected by C-peptide levels, increased after 4 h but insulin levels did not change significantly. Blood lactate, 3-hydroxybutyrate, plasma non-esterified fatty acids and plasma glucagon all fell appropriately during treatment. We conclude that quinine, when administered at the recommended dose and rate, does not disrupt blood glucose homeostasis, and is still the drug of choice for severe and complicated malaria in children.

Malaria prophylaxis amongst British residents of Lilongwe and Kasungu districts, Malawi

Questionnaires on various aspects of malaria prophylaxis were distributed to all British residents (adults and children) of Lilongwe and Kasungu districts, Malawi, and were completed and returned by 293 (response rate 89%). Almost all residents used some measures to reduce mosquito contact, and 96% used chemoprophylaxis. Eight different chemoprophylactic regimens were used. Proguanil, alone or with chloroquine, was the most popular agent despite being associated with mouth ulcers in 25% of residents. Residents on this regimen had in general obtained their advice from a British source, and 75% considered they were adequately informed on the subject. This regimen was the most effective in preventing malaria attacks in the previous 12 months, even though over half those on proguanil alone were taking an inadequate dose. Residents on other chemoprophylactic regimens in general obtained their advice elsewhere, considered they were inadequately informed, and had a higher incidence of malaria. Whatever the regimen, 27% of adult residents would discontinue prophylaxis prematurely on return to the United Kingdom. Results suggest that more needs to be done to provide regular, precise and up-to-date information on malaria prophylaxis to British residents in malaria endemic areas.

Evaluation of the sensitivity in vivo and in vitro of Plasmodium falciparum malaria to quinine in an area of full sensitivity to chloroquine

The sensitivity of Plasmodium falciparum to quinine in Nigeria was examined in vivo and in vitro prior to the re-introduction of the drug into malaria therapy in that country in the face of spreading chloroquine resistance in Africa. The parasites showed full sensitivity in vivo to quinine, with a mean parasite clearance time of 2.4 d and a mean fever clearance time of 1.4 d. Using the in vitro microculture technique, the Nigerian isolates were found to have a minimum inhibitory concentration (IC) of 1.28 mumol quinine/litre blood-medium mixture. The IC50 and IC99 were 0.25 mumol/litre and 0.8 mumol/litre respectively. The study afforded an opportunity to compare the sensitivity of P. falciparum to quinine and chloroquine in a population in which chloroquine resistance was not a problem and the results showed slower parasitological and clinical response to quinine than to chloroquine.

Comparative efficacy of alternative primary therapies for Plasmodium falciparum infections in Malawi

In Malawi, where high levels of chloroquine resistance were shown using a modified 7-day in vivo test, amodiaquine and pyrimethamine-sulfadoxine were evaluated as alternative initial therapies for Plasmodium falciparum infections in children under 5 years old. Therapy success rates, judged by parasite clearance by day 7 after initiation of therapy, were significantly greater among 39 children treated with amodiaquine at 10 mg/kg (90%), 37 receiving amodiaquine at 25 mg/kg (97%), and 34 receiving pyrimethamine-sulfadoxine (100%) at a dose of 25 mg sulfadoxine/kg, than among those treated with chloroquine at a dose of 25 mg/kg (59%) (P = 0.01). Extension of the follow-up period of those receiving amodiaquine (25 mg/kg) and pyrimethamine-sulfadoxine to 21 d revealed a progressively increasing rate of parasite recrudescence in the amodiaquine group (34%), but no recrudescence in the pyrimethamine-sulfadoxine group. These results suggest that, in Malawi, amodiaquine and pyrimethamine-sulfadoxine are superior to chloroquine in producing prompt clearance of P. falciparum parasites among young children, and that pyrimethamine-sulfadoxine alone is superior to the 4-aminoquinolines in sustaining P. falciparum clearance.