A randomized trial of chloroquine, amodiaquine and pyrimethamine-sulphadoxine in Gambian children with uncomplicated malaria

Reemergence of chloroquine (CQ) analogs as multi-targeting antimalarial agents: a review

Amongst several communicable diseases (CDs), malaria is one of the deadliest parasitic disease all over the world, particularly in African and Asian countries. To curb this menace, numbers of antimalarial agents are being sold as over the counter (OTC) drugs. Chloroquine (CQ) is one of them and is one of the oldest, cheapest, and easily available synthetic agents used to curb malaria. Unfortunately, after the reports of CQ-resistance against different strains of malarial parasite strains worldwide, scientist are continuously modifying the core structure of CQ to get an efficient drug. Interestingly, several new drugs have been emerged in due course having unique and enhanced properties (like dual stage inhibitors, resistance reversing ability etc.) and are ready to enter into the clinical trial. In this course, some new agents have also been discovered which are; though inactive against CQS strain, highly active against CQR strains. The present article describes the role of modification of the core structure of CQ and its effects on the biological activities. Moreover, the attempt has also been made to predict the future prospects of such drugs to reemerge as antimalarial agents.

Efficacy of chloroquine, amodiaquine and sulphadoxine-pyrimethamine for the treatment of uncomplicated falciparum malaria: revisiting molecular markers in an area of emerging AQ and SP resistance in Mali

Background

To update the National Malaria Control Programme of Mali on the efficacy of chloroquine, amodiaquine and sulphadoxine-pyrimethamine in the treatment of uncomplicated falciparum malaria.

Methods

During the malaria transmission seasons of 2002 and 2003, 455 children – between six and 59 months of age, with uncomplicated malaria in Kolle, Mali, were randomly assigned to one of three treatment arms. In vivo outcomes were assessed using WHO standard protocols. Genotyping of msp1, msp2 and CA1 polymorphisms were used to distinguish reinfection from recrudescent parasites (molecular correction).

Results

Day 28 adequate clinical and parasitological responses (ACPR) were 14.1%, 62.3% and 88.9% in 2002 and 18.2%, 60% and 85.2% in 2003 for chloroquine, amodiaquine and sulphadoxine-pyrimethamine, respectively. After molecular correction, ACPRs (cACPR) were 63.2%, 88.5% and 98.0% in 2002 and 75.5%, 85.2% and 96.6% in 2003 for CQ, AQ and SP, respectively. Amodiaquine was the most effective on fever. Amodiaquine therapy selected molecular markers for chloroquine resistance, while in the sulphadoxine-pyrimethamine arm the level of dhfr triple mutant and dhfr/dhps quadruple mutant increased from 31.5% and 3.8% in 2002 to 42.9% and 8.9% in 2003, respectively. No infection with dhps 540E was found.

Conclusion

In this study, treatment with sulphadoxine-pyrimethamine emerged as the most efficacious on uncomplicated falciparum malaria followed by amodiaquine. The study demonstrated that sulphadoxine-pyrimethamine and amodiaquine were appropriate partner drugs that could be associated with artemisinin derivatives in an artemisinin-based combination therapy.

Efficacy of amodiaquine in the treatment of uncomplicated falciparum malaria in young children of rural north-western Burkina Faso

Background

Combination therapy has become a new paradigm in malaria treatment. Amodiaquine is a common partner drug in different malaria combination therapies used or investigated in sub-Saharan Africa, but data on its efficacy as a single drug are scarce.

Methods

The objective of the study was to determine the efficacy of amodiaquine against falciparum malaria in neighbouring rural and urban areas of north-western Burkina Faso. The study was designed as an uncontrolled trial in children aged 6–59 months with uncomplicated falciparum malaria in the Nouna Health District.

Results

During the rainy season 2005, 117 children were enrolled, 62 from the rural and 55 from the urban study area. The crude adequate clinical and parasitological response (ACPR) rate was 103/117 (88%) by day 14 but decreased to 28/117 (24%) by day 28. After PCR correction for reinfections, ACPR rates were 108/117 (92%) and 71/117 (61%) by day 14 and day 28, respectively. There were no significant differences in efficacy between urban and rural areas. The Plasmodium falciparum crt K76T mutation not predict AQ failure, but was selected in parasites re-appearing following treatment. No serious adverse events occurred and only 16 other adverse events were recorded.

Conclusion

Compared to chloroquine, amodiaquine is more effective against uncomplicated falciparum malaria in Burkina Faso. However, a considerable degree of amodiaquine resistance already exists and it is currently unclear how this resistance will develop when amodiaquine in combination with other drugs is used on a large scale.

Trial registration

Current Controlled Trials ISRCTN73824458.

Safety and efficacy of methylene blue combined with artesunate or amodiaquine for uncomplicated falciparum malaria: a randomized controlled trial from Burkina Faso

BACKGROUND

Besides existing artemisinin-based combination therapies, alternative safe, effective and affordable drug combinations against falciparum malaria are needed. Methylene blue (MB) was the first synthetic antimalarial drug ever used, and recent studies have been promising with regard to its revival in malaria therapy. The objective of this study was to assess the safety and efficacy of two MB-based malaria combination therapies, MB-artesunate (AS) and MB-amodiaquine (AQ), compared to the local standard of care, AS-AQ, in Burkina Faso.

METHODS AND FINDINGS

Open-label randomised controlled phase II study in 180 children aged 6-10 years with uncomplicated falciparum malaria in Nouna, north-western Burkina Faso. Follow-up was for 28 days and analysis by intention-to-treat. The treatment groups were similar in baseline characteristics and there was only one loss to follow-up. No drug-related serious adverse events and no deaths occurred. MB-containing regimens were associated with mild vomiting and dysuria. No early treatment failures were observed. Parasite clearance time differed significantly among groups and was the shortest with MB-AS. By day 14, the rates of adequate clinical and parasitological response after PCR-based correction for recrudescence were 87% for MB-AS, 100% for MB-AQ (p = 0.004), and 100% for AS-AQ (p = 0.003). By day 28, the respective figure was lowest for MB-AS (62%), intermediate for the standard treatment AS-AQ (82%; p = 0.015), and highest for MB-AQ (95%; p<0.001; p = 0.03).

CONCLUSIONS

MB-AQ is a promising alternative drug combination against malaria in Africa. Moreover, MB has the potential to further accelerate the rapid parasite clearance of artemisinin-based combination therapies. More than a century after the antimalarial properties of MB had been described, its role in malaria control deserves closer attention.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00354380.

Synthesis and antimalarial activity of new analogues of amodiaquine

In order to determine the real significance of the 4'-phenolic group in the antimalarial activity and/or cytotoxicity of amodiaquine (AQ), analogues for which this functionality was shifted or modified were synthesized. Good in vitro antimalarial activity was obtained for compounds unable to form intramolecular hydrogen bond. Among the compounds synthesized, new amino derivative 5 displayed the greatest selectivity index towards the most CQ-resistant strain tested and was active in mice infected by Plasmodium berghei.

Seasonal carriage of pfcrt and pfmdr1 alleles in Gambian Plasmodium falciparum imply reduced fitness of chloroquine-resistant parasites

BACKGROUND

Observations in natural Plasmodium falciparum populations after removal of failing drugs suggest that there is a fitness cost of drug resistance.

METHODS

To examine the effect of transient removal of drug pressure, we analyzed seasonal changes in the prevalence of chloroquine (CQ)-resistant parasite genotypes in The Gambia. Parasite isolates from 441 children presenting with uncomplicated falciparum malaria over 5 seasons (1998-2002) were linked to weekly rainfall data.

RESULTS

The prevalence of CQ-resistant parasites increased slightly over 5 years, with the 76T allele of pfcrt (odds ratio [OR] per year, 1.16; P=.03) and the 86Y allele of pfmdr1 (OR per year, 1.18; P=.02) becoming significantly more common. However, intraseasonal analysis showed that these alleles decreased in prevalence each dry season. Wild-type parasites with respect to both loci predominated as transmission began each year, with resistant parasites becoming more common as drug use increased. This pattern was seen for both pfcrt-76T (OR per week, 1.09; P=.001) and pfmdr1-86Y (OR per week, 1.07; P=.001) and could not be explained by seasonal changes in the clonal complexity of infections.

CONCLUSIONS

The fitness cost of CQ resistance works against the persistence of resistant parasites through the dry season.

Resistência à sulfadoxina-pirimetamina em Maputo, Moçambique: presença de mutações nos genes dhfr e dhps do Plasmodium falciparum

Foram analisadas a freqüência e distribuição de mutações nos genes dihidrofolato redutase e dihidropteroato sintetase do Plasmodium falciparum, usando a metodologia de reação em cadeia da polimerase e polimorfismos de hidrólise por enzimas de restrição, em amostras de sangue infectado proveniente de crianças moçambicanas, residentes em Maputo. A análise foi feita antes e 7 dias após o tratamento com sulfadoxina-pirimetamina (S/P). Os resultados mostraram a ocorrência de mutações pontuais nos genes estudados e a presença de combinações de três alelos em dhfr (51Ile, 59Arg e 108Asn) e do quintúplo mutante (dhfr 51Ile, 59Arg, 108Asn e dhps 437Gly, 540Glu), ambas situações associadas à falha terapêutica no sétimo dia após tratamento com S/P. Esses achados mostram a importância de se estudar a resistência à S/P em Moçambique, e como os marcadores moleculares de resistência aos antimaláricos podem fornecer dados importantes para a política nacional de controlo da malária.

Continued efficacy of sulfadoxine-pyrimethamine as second line treatment for malaria in children in Guinea-Bissau

BACKGROUND

Sulfadoxine-pyrimethamine (S/P) is widely used for treatment of failures following the first line treatment for malaria in Africa. In Guinea-Bissau, it has been recommended as second line therapy by the National Malaria Programme since 1996. In order to monitor any change of the in vivo sensitivity, the efficacy of S/P was studied immediately before the introduction of the drug and 6-9 years later.

METHODS

Children participating in clinical in vivo studies were given S/P if having late clinical treatment failure following the treatment with quinine, chloroquine, or amodiaquine. Parasitological and clinical failures were evaluated during a 35-day follow-up. During the first study period whole blood sulfadoxine concentrations were measured on day 7.

RESULTS

Altogether, 56 children failed the initial treatment and were included in 1995/1996 as well as 55 children in 2002/2004. The PCR-uncorrected adequate clinical and parasitological response rates on day 28 were 94% and 91%, and on day 35 they were 89% and 91%, respectively, in the two periods. No difference between median blood drug concentration in children with and without treatment failure was observed.

INTERPRETATION

The efficacy of S/P as second line treatment for uncomplicated malaria has remained unchanged in spite of a relatively high level of genetic markers associated with Plasmodium falciparum resistance to S/P previously found in the area.

Efficacy, safety, and tolerability of amodiaquine plus sulphadoxine-pyrimethamine used alone or in combination for malaria treatment in pregnancy: a randomised trial

BACKGROUND

The widespread increase in resistance of Plasmodium falciparum to chloroquine and sulphadoxine-pyrimethamine threatens the use of these drugs for malaria treatment in pregnancy. We aimed to assess the safety and efficacy of amodiaquine alone or in combination with sulphadoxine-pyrimethamine as alternative regimens.

METHODS

Pregnant women with a gestational age of 16 weeks or more who attended antenatal clinics at a district hospital in Ghana were screened for malaria with OptiMAL dipsticks. 900 pregnant women who had a positive test result and P falciparum asexual stage parasitaemia were enrolled and randomly assigned chloroquine, sulphadoxine-pyrimethamine, amodiaquine, or amodiaquine plus sulphadoxine-pyrimethamine. The primary outcome was parasitological failure by day 28 of treatment. Women were seen on days 3, 7, 14, and 28 after the start of treatment to assess the effect of treatment on peripheral parasitaemia, haemoglobin concentration, white-blood-cell count, and liver function. Additionally, reports of adverse effects were solicited and monitored during follow-up visits. Analysis was by intention to treat. This trial is registered with the US National Institute of Health clinical trials database number NCT00131703.

FINDINGS

PCR-corrected parasitological failure by day 28 was 14%, 11%, 3%, and 0% in the women assigned chloroquine, sulphadoxine-pyrimethamine, amodiaquine, and amodiaquine plus sulphadoxine-pyrimethamine, respectively (p<0.0001). No serious liver toxic effects or white-blood-cell dyscrasias were noted. Minor side-effects were reported more often on day 3 by women receiving amodiaquine (86%) or amodiaquine plus sulphadoxine-pyrimethamine (90%) than those receiving sulphadoxine-pyrimethamine (48%) or no antimalarial drugs (34%; p<0.0001 for every comparison).

INTERPRETATION

Amodiaquine alone or in combination with sulphadoxine-pyrimethamine, although associated with minor side-effects, is effective when used to treat malaria in pregnancy.

Randomised trial of chloroquine/sulphadoxine-pyrimethamine in Gambian children with malaria: impact against multidrug-resistant P. falciparum

OBJECTIVES

In the Gambia, the combination of chloroquine (CQ) and sulphadoxine-pyrimethamine (SP) has replaced CQ monotherapy for treatment of malaria caused by Plasmodium falciparum. We measured the efficacy of the combination CQ/SP, and the prevalence of parasites carrying alleles associated with resistance to CQ or SP.

DESIGN

We conducted a single-blind, randomised, controlled trial to compare the efficacy of CQ/SP to that of SP or CQ alone.

SETTING

The study took place in the town of Farafenni and surrounding villages in the Gambia.

PARTICIPANTS

Participants were children aged 12 mo to 10 y presenting as outpatients with uncomplicated P. falciparum malaria.

INTERVENTIONS

500 children were randomised to receive CQ, SP, or CQ/SP as supervised treatment and actively followed over 28 d.

OUTCOME MEASURES

Primary outcome was parasitaemia at any time during follow-up. Secondary outcomes were PCR-confirmed recrudescent infections among treatment failures, and clinical failure requiring rescue medication by day 28. Pretreatment parasite isolates from 161 patients were tested for the presence of resistance-associated genetic markers.

RESULTS

The prevalence of parasitological failure by day 28 for the CQ group was 60.3%, compared to 17.6% for SP (odds ratio [OR], 0.106; 95% confidence interval [CI], 0.057-0.194; p < 0.001) and 13.9% for CQ/SP (OR versus CQ, 0.140; 95% CI, 0.078-0.250; p < 0.001). There was no difference between the SP and CQ/SP groups (OR, 1.324; 95% CI, 0.705-2.50). The projected prevalence of PCR-corrected treatment failure was 30.2, 6.06, and 3.94% in the CQ, SP, and CQ/SP groups, respectively. The pfdhfr-triple mutant and pfdhps-437G mutation were common, with prevalences of 67.4 and 51.2%, respectively. Pretreatment carriage of pfdhps-437G and of multidrug-resistant parasite genotypes was associated with treatment failure in the SP group, but not in the CQ or CQ/SP groups.

CONCLUSIONS

The combination of CQ/SP was an efficacious treatment for uncomplicated malaria in Gambian children in this study, but the frequent occurrence of multidrug-resistant parasites suggests that this observed efficacy is not sustainable.

Pattern of cause-specific childhood mortality in a malaria endemic area of Burkina Faso

BACKGROUND

Reliable mortality data are a prerequisite for planning health interventions, yet such data are often not available in developing countries, particularly in sub-Saharan Africa (SSA). Demographic surveillance systems (DSS) implementing the verbal autopsy (VA) method are the only possibility to observe cause-specific mortality of a population on a longitudinal basis in many countries.

METHODS

This paper reports all-cause and cause-specific mortality rates in children under the age of five years from 1999 until 2003 in a malaria holoendemic area of north-western Burkina Faso. The DSS of the Nouna Health Research Centre, in which VA data were analysed, covers a rural population of about 30,000 (41 villages) and an urban population of about 25,000 (Nouna town).

RESULTS

A total of 1,544 deaths were analysed, 87 (6%), 225 (14%), 317 (21%) and 915 (59%) of which occurred in the periods < 1 month, 1-5 months, 6-11 months and 1-4 years respectively. All cause mortality rates of children under five years were higher in the rural than the urban area (34 vs 24 per 1,000 person-years) and in the rainy than the dry season (35 vs 29 per 1,000 person-years). Malaria was the most frequent diagnosis (42%) with peak mortality rates in infants aged 6-11 months.

CONCLUSION

Malaria is the most important cause of death in this remote area of SSA, even considering the low specificity of malaria diagnosis in young children. Strengthening the existing malaria control tools is of prime importance to reduce the high childhood mortality in the endemic areas of SSA.

Bibliometric analysis of research published in Tropical Medicine and International Health 1996-2003

We examine the bibliometric profile of Tropical Medicine and International Health using the subjects of the articles published and the geographical distribution of the authors. The most common subject areas of papers published during 1996-2003 are highlighted, and the most cited papers indicated.

Efficacy of pyrimethamine-sulfadoxine in young children with uncomplicated falciparum malaria in rural Burkina Faso

The efficacy of pyrimethamine-sulfadoxine in the treatment of uncomplicated falciparum malaria in young children of a malaria holoendemic area in rural Burkina Faso is reported. Of 28 children treated with a standard single dose of pyrimethamine-sulfadoxine and followed-up over 14 days, only one Late Treatment Failure and four Late Parasitological Failures were observed, all with low-grade parasitaemia. In this area of very restricted use of pyrimethamine-sulfadoxine, the drug appears to be still sufficiently effective in the treatment of malaria. These findings provide further evidence for the justification of continued use of pyrimethamine-sulfadoxine as a second-line treatment for malaria in Burkina Faso.

History, dynamics, and public health importance of malaria parasite resistance

Despite considerable efforts, malaria is still one of the most devastating infectious diseases in the tropics. The rapid spread of antimalarial drug resistance currently compounds this grim picture. In this paper, we review the history of antimalarial drug resistance and the methods for monitoring it and assess the current magnitude and burden of parasite resistance to two commonly used drugs: chloroquine and sulfadoxine-pyrimethamine. Furthermore, we review the factors involved in the emergence and spread of drug resistance and highlight its public health importance. Finally, we discuss ways of dealing with such a problem by using combination therapy and suggest some of the research themes needing urgent answers.

Addition of artesunate to chloroquine for treatment of Plasmodium falciparum malaria in Gambian children causes a significant but short-lived reduction in infectiousness for mosquitoes

OBJECTIVES

Combination therapy using existing anti-malarials together with artesunate (AS) has been advocated as a method to slow the spread of drug resistance. We assessed the effect on Plasmodium falciparum transmissibility of the addition of AS to chloroquine (CQ) in an area of The Gambia where resistance to CQ is increasing.

METHODS

Gambian children with acute uncomplicated P. falciparum malaria were treated with either CQ monotherapy (n=120) or the combination of CQ plus three doses of AS (CQ/AS; n=352). Post-treatment sexual-stage parasitaemia was assessed during a 4-week follow-up period. Experimental infections of Anopheles gambiae s.s. mosquitoes were performed with blood from patients who were carrying gametocytes 7 days after starting treatment (n=69).

RESULTS

The addition of AS significantly reduced post-treatment prevalence and mean density of gametocytes in the first 14 days (day 7: 43.7% vs. 12.4%, 62.4/microl vs. 6.2/microl; day 14: 32.9% vs. 3.7%; 21.9/microl vs. 5.2/microl; CQ vs. CQ/AS), although by day 28 the benefits of the combination were substantially less marked (40.5% vs. 21.8%; 23.0/microl vs. 63.1/microl; CQ vs. CQ/AS). The duration of gametocyte carriage over the study period was significantly lower in the CQ/AS group (5.2 days vs. 1.5 days; CQ vs. CQ/AS). The estimated infectious proportion of children at day 7 was also lower in the combination group (19.2% vs. 3.4%; CQ vs. CQ/AS), as were the proportion of mosquitoes infected and mean oocyst density (11.5% vs. 0.9%; 0.3 vs. 0.01; CQ vs. CQ/AS). Treatment failure was associated with threefold and twofold higher gametocyte carriage rates during follow-up in CQ and CQ/AS groups, respectively (P<0.001 in both cases), and 26-fold and 2.3-fold higher intensity of infection at day 7 among CQ- and CQ/AS-treated children, respectively (P=0.002 and 0.30, respectively).

CONCLUSION

The benefits of adding AS to CQ monotherapy in lowering gametocyte prevalence and density were transient, suggesting that the addition of AS delayed, but did not prevent, the emergence of gametocytes. This is consistent with our finding that treatment failure, and thus the presence of CQ-resistant parasites, was significantly associated with a higher gametocyte carriage rate in both treatment groups. At day 7, CQ monotherapy significantly favoured transmission of resistant infections, which showed an 11-fold greater intensity of transmission compared with infections that were successfully treated. In contrast, the combination of CQ/AS did not significantly favour resistant infections at day 7. We conclude that significant transmission-reduction is achieved by the combination but is not maintained because of the recrudescence of CQ-resistant parasites.

Asymptomatic, recrudescent, chloroquine-resistant Plasmodium falciparum infections in Nigerian children: clinical and parasitological characteristics and implications for the transmission of drug-resistant parasites

The clinical features of their primary Plasmodium falciparum infections and of the recrudescent infections that emerged after chloroquine (CQ) treatment were evaluated in 48 children. Compared with the primary infections, the recrudescent infections were accompanied by significantly fewer symptoms and lower densities of parasitaemia but a much higher gametocytaemia:parasitaemia ratio (0.051 v. 0.00097; P = 0.0000000). There was a negative correlation between the recrudescent parasitaemia and the time elapsing between its detection and the subsequent onset of symptoms (r = -0.44; P = 0.006). The recrudescent parasitaemia was significantly lower [with geometric means and (ranges) of 117 (40-9756) v. 1112 (30-25,592) asexual forms/microl; P = 0.009] and the recrudescent gametocytaemia:parasitaemia ratio significantly higher (0.59 v. 0.024; P = 0.0000002) in those who were asymptomatic for at least 5 days after detection of the recrudescent parasitaemia than in those who were symptomatic at recrudescence. The disposition kinetics of the gametocytaemias in 18 primary infections--from nine children who failed CQ treatment and nine other children, matched for age and gender with the failures, who were CQ-treatment successes--were analysed. The results showed that the maximum gametocytaemia, time taken to reach the maximum gametocytaemia, the half-life of the gametocytaemia and the area inscribed by the plot of gametocytaemia against time were significantly higher, and the clearance of gametocytaemia significantly slower, in the children with primary infections that recrudesced. It therefore appears that continuing the use of CQ in areas where some parasites are resistant to the drug may confer survival and propagation advantages on the resistant parasites.

Malaria morbidity, treatment-seeking behaviour, and mortality in a cohort of young children in rural Burkina Faso

OBJECTIVE

To describe the pattern of fever-associated morbidity, treatment-seeking behaviour for fever episodes, and cause-specific mortality in young children of a malaria-holoendemic area in rural Burkina Faso.

METHODS

In a longitudinal community-based intervention study, 709 representative children aged 6-31 months were followed daily over 6 months (including the main malaria transmission period) through village-based field staff.

RESULTS

Of 1848 disease episodes, 1640 (89%) were fever episodes, and of those, 894 (55%) were attributed to malaria (fever + > or =5000 parasites/microl). Eighty-five percent of fever episodes were treated, mainly with chloroquine and paracetamol, 69% of treatments took place in households, 16% in local health centres, 13% in villages, and 1% in hospitals. Treatment-seeking in a health centre or hospital was associated with accessibility and disease severity. Cerebral malaria and malnutrition-associated diarrhoea were the most frequently diagnosed causes of death. While most children with a post-mortem diagnosis of diarrhoea had not received any treatment, children who died of malaria had often received insufficient treatment. In particular, there was a lack of an appropriate second-line treatment at formal health services after chloroquine treatment had failed to resolve symptoms.

CONCLUSIONS

These findings call for more effective prevention and treatment of malaria, malnutrition and diarrhoea in rural African communities, as well as for better supervision of existing malaria treatment guidelines in formal health services.

Hospital costs of high-burden diseases: malaria and pulmonary tuberculosis in a high HIV prevalence context in Zimbabwe

This paper explores the measurement of hospital costs and efficiency in a context where data is scarce, incomplete or of poor quality. It argues that there is scope for using tracers to examine and compare hospital cost structures and relative efficiency in such contexts. Two high-burden diseases, malaria and pulmonary tuberculosis, are used as tracers to calculate the average costs of inpatient care at selected tertiary hospitals. This study shows that it is feasible to prospectively collect cost data for specific diseases and explore in detail both patient cost distribution and susceptible areas for efficiency improvement. The present study found that the critical source of efficiency variation in public hospitals in Zimbabwe lies in the way hospital beds are used.

Combination of drug level measurement and parasite genotyping data for improved assessment of amodiaquine and sulfadoxine-pyrimethamine efficacies in treating Plasmodium falciparum malaria in Gabonese children

Many African countries currently use a sulfadoxine-pyrimethamine combination (SP) or amodiaquine (AQ) to treat uncomplicated Plasmodium falciparum malaria. Both drugs represent the last inexpensive alternatives to chloroquine. However, resistant P. falciparum populations are largely reported in Africa, and it is compulsory to know the present situation of resistance. The in vivo World Health Organization standard 28-day test was used to assess the efficacy of AQ and SP to treat uncomplicated falciparum malaria in Gabonese children under 10 years of age. To document treatment failures, molecular genotyping to distinguish therapeutic failures from reinfections and drug dosages were undertaken. A total of 118 and 114 children were given AQ or SP, respectively, and were monitored. SP was more effective than AQ, with 14.0 and 34.7% of therapeutic failures, respectively. Three days after initiation of treatment, the mean level of monodesethylamodiaquine (MdAQ) in plasma was 149 ng/ml in children treated with amodiaquine. In those treated with SP, mean levels of sulfadoxine and pyrimethamine in plasma were 100 microg/ml and 212 ng/ml, respectively. Levels of the three drugs were higher in patients successfully treated with AQ (MdAQ plasma levels) or SP (sulfadoxine and pyrimethamine plasma levels). Blood concentration higher than breakpoints of 135 ng/ml for MdAQ, 100 micro g/ml for sulfadoxine, and 175 ng/ml for pyrimethamine were associated with treatment success (odds ratio: 4.5, 9.8, and 11.8, respectively; all P values were <0.009). Genotyping of merozoite surface proteins 1 and 2 demonstrated a mean of 4.0 genotypes per person before treatment. At reappearance of parasitemia, both recrudescent parasites (represented by common bands in both samples) and newly inoculated parasites (represented by bands that were absent before treatment) were present in the blood of most (51.1%) children. Only 3 (6.4%) therapeutic failures were the result not of treatment inefficacy but of new infection. In areas where levels of drug resistance and complexity of infections are high, drug dosage and parasite genotyping may be of limited interest in improving the precision of drug efficacy measurement. Their use should be weighted according to logistical constraints.

Plasmodium falciparum: in vitro interactions of artemisinin with amodiaquine, pyronaridine, and chloroquine

In the scenario of drug-resistant Plasmodium falciparum malaria combination therapy represents an effective approach. Artemisinin and its derivatives are of special interest because they represent the most effective group of compounds against multidrug-resistant malaria with a rapid onset of action and a short half-life. Interactions of artemisinin with amodiaquine, pyronaridine, and chloroquine were therefore investigated against three strains of P. falciparum using a 48-h in vitro culture assay. Two of the strains were chloroquine sensitive and one was partially chloroquine resistant. Observed effective concentrations (O) of the combined compounds at different concentration ratios were calculated for different degrees of inhibition (EC50, EC90, EC99) and compared to expected calculated effective concentrations (E) using a probit method. Synergism with mean O/E EC90 values of 0.25 and 0.8 were found with the combination of artemisinin and the two Mannich bases, amodiaquine and pyronaridine, respectively, whereas chloroquine showed addition with a mean value of 1.2. Although both amodiaquine and chloroquine are 4-aminoquinolines, their interaction with artemisinin appears to be different. The combination of artemisinin with amodiaquine represents an important option for the treatment of falciparum malaria.

Synthesis and in vitro and in vivo antimalarial activity of new 4-anilinoquinolines

A new series of 4-anilinoquinolines with two proton-accepting side chains has been synthesized. Antimalarial activity and levels of cytotoxicity upon both MRC-5 cells and macrophages were found to be highly dependent upon the features of these side chains. Several compounds were found to be active in the low nanomolar range, against both chloroquine-sensitive and -resistant strains of Plasmodium falciparum in vitro. From among them, a morpholino derivative cured mice infected by Plasmodium berghei and displayed a lower toxicity than amodiaquine upon mouse macrophages.

Amodiaquine, sulfadoxine/pyrimethamine, and combination therapy for treatment of uncomplicated falciparum malaria in Kampala, Uganda: a randomised trial

BACKGROUND

Increasing Plasmodium falciparum resistance to chloroquine in sub-Saharan Africa necessitates use of alternative antimalarial agents. Affordable alternative treatments include sulfadoxine/pyrimethamine and amodiaquine. Combination of antimalarial agents can increase therapeutic efficacy and delay emergence of drug resistance. We compared the efficacy of sulfadoxine/pyrimethamine, amodiaquine, and an amodiaquine/sulfadoxine/pyrimethamine combination for treatment of uncomplicated malaria in a region of high chloroquine resistance.

METHODS

Patients with symptoms of uncomplicated falciparum malaria and confirmed disease in Kampala, Uganda, were randomly assigned to receive sulfadoxine/pyrimethamine (25 mg/kg sulfadoxine, and 1.25 mg/kg pyrimethamine) plus placebo; amodiaquine (25 mg/kg) plus placebo; or amodiaquine plus sulfadoxine/pyrimethamine. Patients were followed up for 14 days, and clinical and parasitological outcomes were assessed.

FINDINGS

90% (400/445) of patients enrolled in the study successfully completed 14 days of follow-up. Treatment failure based on clinical criteria occurred in 13 of 131 (10%) patients on sulfadoxine/ pyrimethamine, nine of 131 (7%) on amodiaquine, and four of 138 (3%) on amodiaquine/sulfadoxine/pyrimethamine. Based on parasitological criteria, treatment failed in 26%, 16%, and 10% of these patients, respectively. Amodiaquine/sulfadoxine/pyrimethamine was significantly more effective than sulfadoxine/pyrimethamine alone in children aged younger than 5 years (clinical failure in 3.5% vs 13.9%, respectively, risk difference 10.4% [95% CI, 1.6-19.3] p=0.021; parasitological failure in 12.8% vs 26.4%, risk difference 13.6% [1.2-26.0] p=0.041).

INTERPRETATION

Sulfadoxine/pyrimethamine, amodiaquine, and amodiaquine/sulfadoxine/pyrimethamine were all effective for treatment of uncomplicated falciparum malaria in Uganda. The amodiaquine/sulfadoxine/pyrimethamine combination was the most effective, and could be the optimum low-cost alternative to chloroquine in Africa.

Rapid therapeutic response onset of a new pharmaceutical form of chloroquine phosphate 300 mg: effervescent tablets

OBJECTIVE

To compare the efficiency, safety and taste of two pharmaceutical forms of chloroquine phosphate 300 mg: effervescent tablets against uncoated tablets.

METHOD

An open randomized study with 60 adults who suffered from acute uncomplicated Plasmodium falciparum malaria in three health centres in Nkongsamba health district, Cameroon.

RESULTS

Mean times to fever clearance, symptoms clearance and asexual parasites clearance were longer in the uncoated tablets group: 36 h (range 24-48 h, SD = 16.8) vs. 60 h (range 24-96 h, SD = 31.2, P = 0.001) for fever clearance, 36 h (24-48 h, SD = 16.8) vs. 48 h (24-72, SD = 24, P = 0.001) for symptoms clearance and 48 h (24-72, SD = 1) vs. 72 h (48-96, SD = 24, P = 0.001) for parasitaemia clearance. Uncoated tablets took significantly longer to achieve 50% reduction of the initial asexual parasite density: (mean/SD) 19.2 h/7 vs. 52.8 h/16.8, P < 0.00001. The adverse effects in the two groups were similar, P > 0.05. The cure rate at day 7 in the two groups was similar, P > 0.05. There was no chloroquine resistance in the effervescent tablets group but one RI and one RII resistance in the uncoated tablets group. The taste of the two pharmaceutical forms was significantly different, P < 0.00001. Effervescent tablets tasted sweet (score = 7.93), whereas uncoated tablets were bitter (score = 2.07).

CONCLUSION

Effervescent tablets of chloroquine phosphate 300 mg work faster than uncoated tablets and because of their safe use and sweet taste achieve good therapeutic compliance.

Parasitaemia and gametocytaemia after treatment with chloroquine, pyrimethamine/sulfadoxine, and pyrimethamine/sulfadoxine combined with artesunate in young Gambians with uncomplicated malaria

As part of a study to assess the infectivity of gametocytes after treatment with four antimalarial regimens, the efficacy of each treatment was also determined. From September to December 1998, 598 children with uncomplicated malaria were treated; 135 received chloroquine (CQ) alone, 276 received pyrimethamine/sulfadoxine (Fansidar, PSD) alone, 113 received PSD with a single dose of artesunate (PSD + 1ART) and 74 received PSD combined with three doses of artesunate (PSD + 3ART). On day 28 19/63 (30.2%; 95% C.I. 19.2% to 43.1%) of children treated with CQ alone, 5/134 (3.7%; 95% C.I. 1.2% to 8.5%) treated with PSD alone, 1/71 (1.4%, 95% C.I. 0.0% to 7.9%) treated with PSD + 1ART and 0/45 (0.0%; 95% C.I. 0.0% to 7.9%) treated with PSD + 3ART were parasitaemic. The proportion of children with gametocytes on day 7 after treatment with CQ alone was 16/89 (18.0%; 95% C.I. 10.6% to 27.6%), 98/174 (56.3%; 95% C.I. 48.6% to 63.8%) after treatment with PSD alone, 8/70 (11.4%; 95% C.I. 5.1% to 21.3%) after treatment with PSD + 1ART and 4/46 (8.7%; 95% C.I., 2.4% to 20.8%) after treatment with PSD + 3ART. CQ thus has a lower efficacy than PSD or either of the PSD and artesunate combinations. Use of PSD alone as an alternative first line treatment results in a very high post-treatment gametocyte prevalence that is likely to enhance transmission. There would be greater and more sustainable benefits from using PSD and artesunate combinations.

The comparative efficacy of chloroquine and sulfadoxine-pyrimethamine for the treatment of uncomplicated falciparum malaria in Kampala, Uganda

Chloroquine (CQ) remains the first-line treatment for uncomplicated malaria in much of Africa despite the growing problem of resistance to this drug. Sulfadoxine-pyrimethamine (SP) is often used after CQ treatment failure and has replaced CQ as the first-line treatment in parts of Africa. To compare the efficacy of these 2 regimens, we evaluated, in March-August 1999, clinical and parasitological responses over 28 days in 214 children and adults from Kampala, Uganda, with uncomplicated falciparum malaria. Compared to SP, significantly more patients treated with CQ developed early or late clinical failure (54% vs 11%, P < 0.001) and parasitological failure (72% vs 30%, P < 0.001) during 14 days of follow-up. The risk of treatment failure occurring after day 14 was similar between the 2 treatment groups. Among those treated with CQ, children aged < 5 years were at higher risk of clinical failure than older individuals (76% vs 28%, P < 0.001), an association not seen with SP (11% vs 10%, P = 0.91). Although early parasite clearance was significantly better in the SP group (P = 0.001), fever clearance at day 3 was the same (CQ 85%, SP 86%). These and other recent findings suggest that consideration be given to replacing CQ as the first-line therapy for uncomplicated malaria in Uganda, particularly in young children.

Anti-NANP antibody and treatment efficacy in patients with acute uncomplicated falciparum malaria attacks

African patients originating from the hypoendemic, urban area of Greater Dakar (Senegal, West Africa) who presented with an acute Plasmodium falciparum infection were studied using an in-vivo chloroquine sensitivity assay for 28 days. Forty-seven patients with acute malaria infections were treated with 25 mg/body weight of chloroquine. Adequate responses to treatment were observed in 24 patients (51%), whereas 23 (49%) were resistant. On the day of admission, these two groups of patients were comparable with respect to age, level of parasitemia and delay before initiation of treatment, but not with respect to gametocyte prevalence which was higher in patients resistant to therapy (48%) than in those who responded to treatment (17%). In order to evaluate whether the therapeutic response was associated with any given specific immune response, antibody activities against different stages of the parasite cycle were evaluated: anti-NANP repeats (i.e. antisporozoite stage antigen), anti-Pfs 45 kDa (i.e. antigametocyte stage antigen), and anti-MSP3 (i.e. antimerozoite stage antigen) antibodies were measured by ELISA at day 0 (i.e. on the day of admission and before initiation of treatment), day 7 and day 28. No significant differences between treatment-sensitive and treatment-resistant infections were observed for antibody prevalences and optical densities, except at day 0, when the prevalence of antibodies against NANP repeats was 2.4 times more frequent in the group of patients with a propitious response to treatment: 62.5% of the patients with an infection sensitive to chloroquine had anti-NANP antibodies, whereas only 26.1% of the patients resistant to chloroquine treatment had such a humoral response. These observations are discussed in relation to (1) the finding that gametocyte prevalence was markedly increased at a time when resistance to antimalarial treatment was observed; (2) the possibility that the efficacy of the therapeutic response could be the result of the combined effects of treatment and the individual immune status of the patients at the time of drug cure; and (3) the presence of detectable anti-NANP activity as potential indicator of the level of premunition acquired in an area of low and seasonal malaria transmission.

Chemoresistance of Plasmodium falciparum in the urban region of Yaounde, Cameroon. Part 2: Evaluation of the efficacy of amodiaquine and sulfadoxine-pyrimethamine combination in the treatment of uncomplicated Plasmodium falciparum malaria in Yaounde, Cameroon

The spread of chloroquine resistance or its stabilization at a high level calls for a change in the therapeutic strategy, including a possible replacement of chloroquine. We assessed and compared the efficacy of amodiaquine and sulfadoxine-pyrimethamine in Yaoundé. Of 140 adults and children > 5 years enrolled in the study, 59 in the amodiaquine and 58 in the sulfadoxine-pyrimethamine treatment group were followed until day 14. The efficacy of amodiaquine was 100%, whereas 12.1% of the patients treated with sulfadoxine-pyrimethamine responded with an early treatment failure. Side effects in both treatment groups were mild and did not require any specific treatment. We did in vitro drug assays for monodesethylamodiaquine (active metabolite of amodiaquine) and pyrimethamine and measured plasma levels of monodesethylamodiaquine, sulfadoxine, and pyrimethamine. Unlike amodiaquine, the results of the in vitro drug sensitivity test for pyrimethamine were not concordant with the clinical response. A wide inter-individual variation in the plasma drug levels was observed. Unlike chloroquine, the mean plasma concentrations did not vary with age. There was no significant difference in the plasma concentrations of sulfadoxine and pyrimethamine between patients responding with an adequate clinical response and those responding with treatment failure. Amodiaquine has several advantages over sulfadoxine-pyrimethamine combination and may be considered to be an effective drug in an endemic zone with a moderate level of chloroquine resistance.

In vivo efficacy study of amodiaquine and sulfadoxine/ pyrimethamine in Kibwezi, Kenya and Kigoma, Tanzania

We conducted two randomized clinical trials to determine the in vivo efficacy of amodiaquine and sulfadoxine/pyrimethamine in treating Plasmodium falciparum malaria. Seventy-five patients under the age of 10 years in Kibwezi, Kenya, and 171 patients in Kigoma, Tanzania, were enrolled for treatment. Due to loss of eight patients in Kibwezi and 37 in Kigoma to follow-up, we used best and worst case scenarios for the parasitological response. The in vivo sensitivity of Plasmodium falciparum to amodiaquine was 75% (no loss to follow-up) in Kibwezi and ranged from 85% in the best to 65% in the worst case scenario in Kigoma. The sensitivity to sulfadoxine/pyrimethamine was 70% to 88% in Kibwezi and 65% to 89% in Kigoma. R1 resistance to amodiaquine was 22% in Kibwezi and varied from 6% in the best to 26% for the worst case scenario in Kigoma. The R1 resistance to sulfadoxine/pyrimethamine was 5% to 23% in Kibwezi and 2% to 26% in Kigoma. R2 resistance was 3% for amodiaquine and 7% for sulfadoxine/pyrimethamine in Kibwezi and 9% in Kigoma for each treatment group. There was no statistically significant difference between treatment groups at either study site, except for a slight difference in R1 resistance in the best case scenario, Kibwezi, in favour of S/P. Although both amodiaquine and sulfadoxine/pyrimethamine resistance seems to be increasing, these antimalarials are still effective in parasite clearance.

A prospective evaluation of a clinical algorithm for the diagnosis of malaria in Gambian children

Diagnosis of clinical malaria remains difficult, especially in areas where a high proportion of the asymptomatic population have parasitaemia, for the symptoms and signs of malaria overlap with those of other common childhood diseases, such as acute lower respiratory tract infections. However, a study of symptoms and signs in a group of children who presented to Farafenni Health Centre, The Gambia with a history of recent fever identified a group of signs and symptoms which were strong predictors of malaria as opposed to other febrile illnesses. Using these predictors, an algorithm was developed which could be used by fieldworkers and which had a similar sensitivity and specificity for the diagnosis of malaria as that of an experienced paediatrician working without laboratory support. This algorithm has been validated prospectively on 518 children who presented to the Medical Research Council clinic at Basse, The Gambia with fever or a history of recent fever during a 10-month period. A fieldworker obtained a detailed history from the parent or guardian of each child and performed a clinical examination which included measurement of axillary temperature and respiratory rate. Packed cell volume was measured and a thick smear was examined for malaria parasites. A malaria score, based on the presence or absence of malaria-related signs and symptoms, was determined for 382 children who were seen at the clinic during the high transmission season. Using the cut-off score which was optimal during the previous retrospective study, a sensitivity of 70% and a specificity of 77% for a diagnosis of malaria was obtained. The optimal cut-off score for the Basse population was a score of 7; this gave a sensitivity of 88% and a specificity of 62%, figures comparable to those obtained by an experienced paediatrician without laboratory support.

Sulfadoxine-pyrimethamine for the treatment of Plasmodium falciparum malaria in Gabonese children

Chloroquine can no longer be recommended as the first-line treatment for falciparum malaria in several parts of Africa, given the increasing resistance of Plasmodium falciparum to this drug. The sulfadoxine-pyrimethamine combination (SP) is obviously an alternative candidate, that has already been selected as first-line antimalarial treatment by a few African countries. However, the extent of resistance to SP appears to be highly variable within Africa. Therefore, we investigated the efficacy of SP to treat uncomplicated malaria attacks in children from south-east Gabon. Sixty-six children presenting with a P. falciparum malaria attack were given a standard regimen of SP, and were followed at Days 3, 7, 14, and 21. No RIII response was observed, but relatively high prevalences of RII (18.2%) and RI (12.1%) were present. Moreover, analysis of the clinical outcome according to CDC criteria showed that initial clinical response was lacking in 8.5% of children, and that clinical failure occurred in 9.1%.

Decline of mortality in children in rural Gambia: the influence of village-level primary health care

Using data from a longitudinal study conducted in 40 villages by the UK MRC in the North Bank Division of The Gambia beginning in late 1981, we examined infant and child mortality over a 15-year period for a population of about 17 000 people. Comparisons are drawn between villages with and without PHC. The extra facilities in the PHC villages include: a paid Community Health Nurse for about every 5 villages, a Village Health Worker and a trained Traditional Birth Attendant. Maternal and child health services with a vaccination programme are accessible to residents in both PHC and non-PHC villages. The data indicate that there has been a marked improvement in infant and under-five mortality in both sets of villages. Following the establishment of the PHC system in 1983, infant mortality dropped from 134/1000 in 1982-83 to 69/1000 in 1992-94 in the PHC villages and from 155/1000 to 91/1000 in the non-PHC villages over the same period. Between 1982 and 83 and 1992-94, the death rates for children aged 1-4 fell from 42/1000 to 28/1000 in the PHC villages and from 45/1000 to 38/1000 in the non-PHC villages. Since 1994, when supervision of the PHC system has weakened, infant mortality rates in the PHC villages have risen to 89/1000 in 1994-96. The rates in the non-PHC villages fell to 78/1000 for this period. The under-five mortality rates in both sets of villages have converged to 34/1000 for 1994-96. When the PHC programme was well supported in the 1980s, we saw significantly lower mortality rates for the 1-4-year-olds. These differences disappeared when support for PHC was reduced after 1994. The differential effects on infant mortality are less clear cut.

Efficacy of artesunate plus pyrimethamine-sulphadoxine for uncomplicated malaria in Gambian children: a double-blind, randomised, controlled trial

BACKGROUND

Resistance to cheap effective antimalarial drugs, especially to pyrimethaminesulphadoxine (Fansidar), is likely to have a striking impact on childhood mortality in sub-Sharan Africa. The use of artesunate (artesunic acid) [corrected] in combination with pyrimethamine-sulphadoxine may delay or prevent resistance. We investigated the efficacy, safety, and tolerability of this combined treatment.

METHODS

We did a double-blind, randomised, placebo-controlled trial in The Gambia. 600 children with acute uncomplicated Plasmodium falciparum malaria, aged 6 months to 10 years, at five health centres were randomly assigned pyrimethaminesulphadoxine (25 mg/500 mg) with placebo; pyrimethamine-sulphadoxine plus one dose of artesunate (4mg/kg bodyweight); or pyrimethamine-sulphadoxine plus one dose 4 mg/kg bodyweight artesunate daily for 3 days. Children were visited at home each day after the start of treatment until parasitaemia had cleared.

FINDINGS

The combined treatment was well tolerated. No adverse reactions attributable to treatment were recorded. By day 1, only 178 (47%) of 381 children treated with artesunate were still parasitaemic, compared with 157 (81%) of 195 children in the pyrimethamine-sulphadoxine alone group (relative risk 1.7 [95% CI 1.5-2.0], p<0.001). Treatment-failure rates at day 14 were 3.1% in the pyrimethamine sulphadoxine alone group, and 3.7% in the one-dose artesunate group (risk difference -0.6% [-4.2 to 3.0]) and 1.6% in the three-dose group (1.5 [1.5-4.5], p=0.048). Symptoms resolved faster in children who received artesunate, but there was no additional benefit for three doses of artesunate over one dose. Children given artesunate were less likely to be gametocytaemic after treatment.

INTERPRETATION

The combined treatment was safe, well tolerated, and effective. The addition of artesunate to malaria treatment regimens in Africa results in lower gametocyte rates and may lower transmission rates.

Amodiaquine for treating malaria

BACKGROUND

Amodiaquine has been widely used to treat malaria. Due to reports of fatal adverse drug reactions, discontinuation or modification of its use has been suggested.

OBJECTIVES

The objective of this review was to assess the effects of amodiaquine for treating malaria.

SEARCH STRATEGY

We searched the Cochrane Infectious Diseases Group trials register and Medline. We also contacted researchers in the field and drug companies.

SELECTION CRITERIA

Randomised and quasi-randomised trials comparing amodiaquine with other treatment for uncomplicated malarial infections in adults and children.

DATA COLLECTION AND ANALYSIS

Both reviewers independently extracted data and assessed trial quality.

MAIN RESULTS

Forty trials were included. Allocation was adequately concealed in three trials. Amodiaquine was more effective than chloroquine for parasite clearance. The combined results of parasite clearance at seven days from 24 trials was 83% for amodiaquine and 56% for chloroquine (odds ratio 4.29, 95% confidence interval 3.51 to 5.24). The odds ratio for parasite clearance at 14 days was 6.00, 95% confidence interval 4.38 to 8.21. Amodiaquine and sulfadoxine/pyrimethamine showed similar results for parasite clearance on day seven, but sulfadoxine/pyrimethamine appeared to be more effective on day 14 and 28. No significant difference for adverse events was observed between amodiaquine and chloroquine and sulfadoxine/pyrimethamine. Reported adverse effects were minor or moderate, not life threatening.

REVIEWER'S CONCLUSIONS

There is some evidence to support the continued use of amodiaquine in the treatment of uncomplicated malaria, although drug resistance should be considered. Monitoring for toxicity should also continue.

A randomized safety and tolerability trial of artesunate plus sulfadoxine--pyrimethamine versus sulfadoxine-pyrimethamine alone for the treatment of uncomplicated malaria in Gambian children

Artemisinin derivatives, such as artesunate, have a short half-life and very rapid anti-malarial activity. Theoretically, using such agents in conjunction with well-established anti-malarial drugs such as sulfadoxine-pyrimethamine may reduce the rate of drug resistance. Such a combination has not previously been used in Africa. We have conducted a pilot safety trial of artesunate (4 mg/kg for 3 days) given with a single dose of sulfadoxine-pyrimethamine (25 mg/kg sulfadoxine) compared to sulfadoxine-pyrimethamine alone among 40 Gambian children with uncomplicated malaria. Both regimens were safe and well tolerated and there were no adverse experiences attributed to the combination. The addition of artesunate resulted in a higher proportion of afebrile children and children with a negative blood film on Day 2, and a reduction in the proportion of gametocyte carriers, when compared to sulfadoxine-pyrimethamine alone.

New 4-aminoquinoline Mannich base antimalarials. 1. Effect of an alkyl substituent in the 5'-position of the 4'-hydroxyanilino side chain

A new series of 4-aminoquinoline Mannich base derivatives have been synthesized, in which the 3'-diethylamino function of amodiaquine (AQ) is replaced by a 3'-tert-butylamino group and an aliphatic hydrocarbon entity is incorporated into the 5'-position of the 4'-hydroxyanilino side chain. Seven alkyl Mannich base derivatives were screened and found to be active against both chloroquine-sensitive and -resistant strains of Plasmodium falciparum in vitro. The propyl and isopropyl alkyl derivatives were found to be the most active; consequently these derivatives were tested against a nonsensitive strain of Plasmodium berghi in vivo and found to be 3-fold more active than AQ, irrespective of the route of administration (oral or intraperitoneal).

A comparison of amodiaquine and sulfadoxine-pyrimethamine as first-line treatment of falciparum malaria in Kenya

A randomized 14-day study in vivo compared the response of Plasmodium falciparum malaria to amodiaquine (35 mg/kg) and sulfadoxine-pyrimethamine (sulfadoxine, 25 mg/kg) in symptomatic outpatients at 2 sites in northern and western Kenya during 1993. Of the 239 patients recruited, 181 (76%) completed the study [84 (46%) on amodiaquine and 97 (54%) on sulfadoxine-pyrimethamine]. There were no significant differences in the parasitological, clinical or haematological responses between the 2 drug groups in both areas, with 18.5% resistance to amodiaquine versus 9.5% for sulfadoxine-pyrimethamine in the north and 35.1% against amodiaquine versus 34.5% for sulfadoxine-pyrimethamine in the west. In both sites defervescence was significantly more rapid with amodiaquine (P < 0.05) and true clinical failure (symptomatic illness with recurrent parasitaemia) was unusual (9%). As high-level resistance to chloroquine is widespread, both drugs are valuable alternatives. However, the significantly higher levels of resistance in the west may be a sign of the increased drug pressure in this holoendemic area and send an important warning concerning resistance to sulfadoxine-pyrimethamine.

Molecular basis of in vivo resistance to sulfadoxine-pyrimethamine in African adult patients infected with Plasmodium falciparum malaria parasites

In vitro sulfadoxine and pyrimethamine resistance has been associated with point mutations in the dihydropteroate synthase and dihydrofolate reductase domains, respectively, but the in vivo relevance of these point mutations has not been well established. To analyze the correlation between genotype and phenotype, 10 Cameroonian adult patients were treated with sulfadoxine-pyrimethamine and followed up for 28 days. After losses to follow-up (n = 1) or elimination of DNA samples due to mixed parasite populations with pyrimethamine-sensitive and pyrimethamine-resistant profiles (n = 3), parasite genomic DNA from day 0 blood samples of six patients were analyzed by DNA sequencing. Three patients who were cured had isolates characterized by a wild-type or mutant dihydrofolate reductase gene (with one or two mutations) and wild-type dihydropteroate synthase gene. Three other patients who failed to respond to sulfadoxine-pyrimethamine treatment carried isolates with triple dihydrofolate reductase gene mutations and either a wild-type or a mutant dihydropteroate synthase gene. Three dihydrofolate reductase gene codons (51, 59, and 108) may be reliable genetic markers that can accurately predict the clinical outcome of sulfadoxine-pyrimethamine treatment in Africa.

Novel aryl-bis-quinolines with antimalarial activity in-vivo

Three rationally designed isomeric aryl-bridged bis-quinolines, N1,Nx-bis(7-chloroquinolin-4-yl)phenylene-1,x-diamines, where x=2, 3 or 4, i.e. o-, m- and p-substituted analogues respectively, were synthesized and evaluated against Plasmodium berghei in-vivo. The compound with x=2 had an ID50 of 30 mg kg(-1), whereas the p-substituted analogue (x=4) was not statistically schizonticidal at either of the two dose levels tested in olive oil-dimethylsulphoxide (5 and 25 mg kg(-1), ID50=60 mg kg(-1) approx.). When the delivery vehicle was changed to saline-DMSO, antimalarial potency increased for the p-substituted compound (ID50 17 mg kg(-1)). In contrast, the m-substituted analogue had marked antimalarial activity (ID50 1.2 mg kg(-1)), which compares favourably with that of chloroquine diphosphate (ID50 = 4.3 mg kg(-1)). The data presented show that the aminomethylene side chain in amodiaquine can be successfully replaced by a 7-halo-4-aminoquinoline, establishing that carbon bridges containing less than four contiguous carbon atoms can be present within highly active aryl-substituted 4-aminoquinoline antimalarials. These results confirm that the presence of an OH group in the aryl bridge is not necessary for antimalarial activity and substantiate the view that, despite the appearance of resistant strains, new and existing aminoquinolines still have an important role in treating malaria.