A randomized comparison of chloroquine,amodiaquine and their combination with pyrimethamine-sulfadoxine in the treatment of acute,uncomplicated, Plasmodium falciparum malaria in children

The increasing resistance of Plasmodium falciparum to antimalarial monotherapy (MT) has created an urgent need for the evaluation of alternative effective, safe, cheap, readily available and affordable, combination treatments (CT) with antimalarial drugs. In the present study, the efficacies of chloroquine (CQ) or amodiaquine (AQ) in the oral treatment of acute, symptomatic, uncomplicated, Plasmodium falciparum malaria were compared with those of oral treatments with the combination of CQ or AQ with pyrimethamine-sulfadoxine (PS). The CQ and AQ were each given at a dose of 10 mg/kg.day for 3 days (days 0, 1 and 2), with or without PS given as a single dose (25 mg sulfadoxine/kg) at presentation (day 0). Overall, 303 children aged 0.5-10 years (74 given CQ, 82 AQ, 72 CQPS and 75 AQPS) were evaluated. The fever-clearance time (FCT) was significantly shorter in those treated with AQPS than in those treated with CQ or CQPS. The proportions of patients with complete clearance of their parasitaemias on days 1 and 2 were significantly larger and the parasite-clearance times (PCT) were all significantly shorter with the drug combinations than with their corresponding MT. For example, the mean (S.D.) PCT were 2.6 (0.8) days for CQ v. 2.1 (0.8) days for CQPS (P=0.0002), and 2.6 (0.7) days for AQ v. 2.1 (0.7) days for AQPS (P=0.00001). The cure 'rates' on days 14, 21 and 28 were also significantly higher with AQ, CQPS and AQPS than with CQ; those on day 28, for example, were 47.2%, 98.7%, 100% and 100% for CQ, AQ, CQPS and AQPS, respectively (P=0.000001). Gametocyte carriages on day 3 or on days 3, 7 and/or 14 combined were significantly lower in those treated with CQPS than in those given CQ; there was no gametocyte carriage in the CT groups on day 28. In the CQ group, eight of 13 children with gametocytaemia on day 3 had a response indicative of resistance. However, the five CQ-resistant infections that were re-treated with AQPS responded promptly, with a PCT significantly shorter than that during the initial treatment with CQ and with a cure 'rate' of 100% on day 28. Adverse reactions to treatment were similar on the first and subsequent days of treatment and were tolerable except for pruritus, which was significantly more common in children treated with CQ alone than in the other treatment groups. Haematological and biochemical parameters were not adversely affected by any treatment. The CQPS and AQPS combinations appear to be well tolerated and may be useful as alternatives to monotherapy with CQ or AQ as resistance to the single drugs develops.     

Plasmodium falciparum genotypes associated with chloroquine and amodiaquine resistance in Guinea-Bissau

Chloroquine is the most commonly used antimalarial in Guinea-Bissau and high doses are routinely prescribed. Blood from 497 patients treated with different doses of chloroquine or amodiaquine were genotyped. Pfcrt and pfmdr1 polymorphisms were identified. Pfmsp2 analysis identified recrudescent infections. The pfcrt 72-76 haplotypes were CVIET and CVMNK. The pfcrt 76T prevalence was 23% at day 0 and 96%, 83% and 100% at recrudescence following treatment with 25 mg/kg and 50 mg/kg of chloroquine and 15 mg/kg of amodiaquine respectively. When treating pfcrt 76T carrying P. falciparum the efficacy of 50 mg/kg and 25 mg/kg of chloroquine was 78% and 34% respectively (P = 0.007). The genetic basis of chloroquine resistance is probably the same in Guinea-Bissau as in the rest of Africa. The low pfcrt 76T prevalence suggests that resistance to normal dose chloroquine does not confer a major advantage to falciparum in Bissau and could be a result of treatment with high-dose chloroquine.     

Plasmodium falciparum in Kisumu, Kenya: differences in sensitivity to amodiaquine and chloroquine in vitro

Sensitivity to amodiaquine and chloroquine was examined in 11 Plasmodium falciparum isolates from Kisumu, Kenya, and three chloroquine-resistant parasites. All 11 Kisumu isolates were sensitive to amodiaquine in vivo. Six of 10 Kisumu isolates successfully tested were more sensitive to amodiaquine in a microtest (minimal inhibitory concentration [MIC], less than or equal to 114 nM for amodiaquine vs 160 nM for chloroquine) and/or 48-hr in vitro tests (MIC, 60 nM for amodiaquine vs 100 nM for chloroquine). All nine successfully cultured Kisumu isolates had a lower 50% inhibitory dose (ID50) for amodiaquine (9.0-18.2 nM) than for chloroquine (24.9-75.4 nM) in a radioisotopic assay. Five were also more sensitive when retested in the 48-hr test. The chloroquine-resistant parasites had reduced in vitro sensitivity to chloroquine (ID50, greater than or equal to 103 nM; MIC, 300 nM) but not to amodiaquine (ID50, less than or equal to 22 nM; MIC, less than or equal to 100 nM). These data indicate that amodiaquine is more potent than chloroquine and should be evaluated for efficacy against P falciparum in areas where RI and RII chloroquine resistance occurs.     

Response of Plasmodium falciparum infections to pyrimethamine-sulfadoxine in Thailand

The results of this study in Thailand indicate that the early response of falciparum infections to a single dose of pyrimethamine-sulfadoxine is influenced by the developmental stages of the parasite present at the time of treatment. Parasite clearance is slower when young rings predominate at the time of treatment. This should be taken into account when considering the clinical management of patients and the comparative efficacy of antimalarials in clearing parasites from the peripheral blood. The 36-48 hr delay in schizonticidal action observed after treatment of febrile infections and the associated decline in blood concentrations of pyrimethamine suggest that a single dose may not be the ideal way of administering this drug combination and may encourage the emergence of drug-resistant parasites.     

Randomized comparison of chloroquine and amodiaquine in the treatment of acute, uncomplicated, Plasmodium falciparum malaria in children.

The increasing resistance of Plasmodium falciparum to chloroquine (CQ) has created an urgent need for the evaluation of alternative, effective, safe, cheap, readily available and affordable antimalarial treatments. In the present study, the efficacy of amodiaquine (AQ) in the treatment of acute, symptomatic, uncomplicated, P. falciparum malaria was compared with that of CQ, each drug being given at 10 mg/kg per day for 3 days (days 0, 1 and 2). The 210 subjects (104 given AQ and 106 CQ) were Nigerian children aged 5 months-12 years. Fever-clearance times (FCT), parasite densities on days 1-4 and parasite-clearance times (PCT) were all significantly lower with AQ than with CQ. Mean (S.D.) PCT, for example, were 2.6 (0.8) days with AQ and 3.0 (1.0) days with CQ (P = 0.001). The cure rates obtained on days 14, 21 and 28 - 98.1% v. 79.3% (P =0.000), 97.1% v. 64.2% (P = 0.00001) and 95.2% v. 58.5% (P = 0.0000000) with AQ and CQ, respectively - were all also significantly higher with AQ. All but two of the 20 subjects who were considered CQ-treatment failures by day 14 (i.e. two RIII, two RII and 16 RI) responded to subsequent treatment with AQ, with PCT (but not FCT) significantly shorter than during their initial treatment with CQ. In siblings in whom there was clustering of infections, the cure rates were 100% with AQ (N =12) and 63.6% with CQ (N = 11; P = 0.03). Adverse reactions to CQ and AQ were similar and tolerable: pruritus in 10 and 11 children in the AQ and CQ groups, respectively, and gastro-intestinal disturbances which occurred in three children from each group. Haematological parameters were not adversely affected by either drug. At least in the setting of the present study, AQ appears more effective than CQ, effective against CQ-resistant infections, and well tolerated by children with acute, uncomplicated, P. falciparum malaria. It may therefore be useful as an alternative to CQ in areas of CQ resistance.     

Efficacy of chloroquine, sulphadoxine-pyrimethamine and amodiaquine for treatment of uncomplicated Plasmodium falciparum malaria in Kajo Keji county, Sudan

To provide advice on the rational use of antimalarial drugs, Médecins Sans Frontières conducted a randomized, an open label efficacy study in Kajo Keji, an area of high transmission of malaria in southern Sudan. The efficacy of chloroquine (CQ), sulphadoxine-pyrimethamine (SP) and amodiaquine (AQ) were measured in a 28-day in vivo study, with results corrected by PCR genotyping. Of 2010 children screened, 115 children aged 6-59 months with uncomplicated Plasmodium falciparum malaria were randomized into each group to receive a supervised course of treatment. Of these, 114, 103 and 111 were analysed in the CQ, SP and AQ groups, respectively. The overall parasitological failure rates at day 28 were 93.9% [95% confidence interval (CI) 87.3-97.3] for CQ, 69.9% (95% CI 60.0-78.3) for SP, and 25.2% (95% CI 17.7-34.5) for AQ. These results provide important missing data on antimalarial drug efficacy in southern Sudan. They indicate that none of the drugs could be used in monotherapy and suggest that even in combination with artemisinin, cure rates might not be efficacious enough. We recommend a combination of artemether and lumefantrine as first-line treatment for uncomplicated P. falciparum malaria cases in Kajo Keji county.     

Efficacy of different primaquine-based antimalarial regimens against Plasmodium falciparum gametocytemia

This study compared the efficacy against Plasmodium falciparum gametocytes of four regimens: amodiaquine-sulfadoxine/pyrimethamine (AQ-SP) and mefloquine-artesunate (MQ-AS), with and without primaquine (PQ) administered with the second dose of the schizonticide (AQ-SP; AQ-SP-PQ; MQ-AS; MQ-AS-PQ). Efficacy was determined by thick smear on days 1, 4 and 8 after the beginning of treatment. A total of 82 patients (19-23/group) were recruited. After AQ-SP administration, gametocytemia steadily increased until day 8. With AQ-SP-PQ, a marked decline in gametocytemia was detected on days 4 and 8. MQ-AS treatment resulted in reduced gametocytemia on days 4 and 8, and with MQ-AS-PQ it was reduced even further. None of the treatments cleared gametocytemia by day 8. Currently, artemisinin-based combination therapies plus PQ are the recommended treatment option against falciparum malaria; however, further studies are required to optimize the use of PQ. Issues to be addressed include the optimal time of administration, treatment duration, optimal daily and total dose, and day of evaluation of the gametocytocidal effect. In falciparum malaria, the WHO recommends a maximum of 4days of treatment; consequently, an effective regimen must clear asexual parasites and symptoms within this time frame. The same criteria should be taken into account when evaluating the anti-gametocyte activity.     

The effects of chloroquine,amodiaquine and chloroquine plus chlorpheniramine on the disposition kinetics of the hepatomegaly associated with acute,uncomplicated, Plasmodium falciparum malaria in children

The effects of chloroquine (CQ), amodiaquine (AQ) and CQ plus chlorpheniramine (a histamine H(1) antagonist that reverses CQ resistance in vitro and in vivo) on the disposition of the enlarged liver associated with acute, symptomatic, uncomplicated, Plasmodium falciparum malaria were evaluated. The subjects, 131 children aged 0.6-12 years who lived in an endemic area of Nigeria, were randomly allotted to the three treatment groups. The cumulative proportions of the children with complete resolution of their enlarged livers at 48, 96, 168 or 336 and 504 h after commencement of treatment were significantly higher in those treated with CQ plus chlorpheniramine (CQCP) than in the other two treatment groups (with P-values of 0.02, 0.001, 0.00000 and 0.00002, respectively). Among those with complete resolution, however, the times to resolution of 50% (HR50) or 90% (HR90) of the liver enlargement were similar in all the treatment groups. Complete resolution of the enlarged liver within 168 h was associated with a sensitive response to each treatment. Overall, in children with complete or partial resolution of their enlarged livers, the area produced by plotting liver size against time (i.e. the area under the curve of hepatomegaly v. time, or AUC(hp)) and the half-life of the hepatomegaly (t(1/2hp)) were significantly lower in the CQCP group than in the other two groups. The volume of blood completely cleared of the 'hepatic pathological processes' which led to the hepatomegaly (CL(Bhp)) and the fractional reduction of AUC(hp) at 48 and 96 h (i.e. AUC(hpFr148) and AUC(hpFr96)) were significantly higher in the CQCP group than in the other treatment groups. When the children with complete resolution of their liver enlargement were considered separately, t(1/2hp) (P=0.0008) but not AUC(hp) was found to be significantly lower, and AUC(hpFr196) (P=0.01) and CL(Bhl) (P=0.002) were found to be significantly higher in the CQCP group than in the other groups. Among the children with only partial resolution of their enlarged livers, the indices of resolution and the kinetic parameters of disposition were similar in all three groups. The data indicate that the addition of chlorpheniramine to chloroquine had a beneficial effect on both the early and late stages of the resolution of the liver enlargement associated with acute, symptomatic, uncomplicated, P. falciparum malaria.     

Changing ideas on chloroquine in Plasmodium falciparum

For 40 years scientists have hotly debated the questions of how chloroquine kills malarial parasites and how resistance to this once first-line antimalarial drug has evolved. While an end to these debates is not in sight, as a result of the complexity of the subject, new findings have come forward that give the discussion a new direction. In this paper we will summarize current knowledge on chloroquine's antimalarial mode of action and the genesis of the resistant phenotype in the human malarial parasite Plasmodium falciparum, with special emphasis on the most recent developments in this field.     

Efficacy of combination therapy with artesunate plus amodiaquine compared to monotherapy with chloroquine, amodiaquine or sulfadoxine-pyrimethamine for treatment of uncomplicated Plasmodium falciparum in Afghanistan

INTRODUCTION: In South and Central Asia resistance to chloroquine (CQ) has reached unmanageable levels, and resistance to sulfadoxine-pyrimethamine (SP) is emerging. Amodiaquine (AQ) is widely used in the region, and elsewhere shows only partial resistance to CQ. In Afghanistan, one option for slowing the spread of resistance and improving treatment outcomes is the use of artemisinin combination therapy (ACT). METHODS: The efficacy of CQ, AQ, SP and amodiaquine plus artesunate (AQ/AS) in the treatment of uncomplicated falciparum malaria was investigated using standard World Health Organization (WHO) procedures. Malaria patients were randomized to four treatment groups: 268 were enrolled and 240 completed the trial. RESULTS: There was a high level of cross-resistance between CQ and AQ resistance: adequate clinical and parasitological response by day 42 was 11% after CQ treatment and 9% after AQ treatment. The trend of treatment failure between AQ and CQ was almost identical. Cure rates were considerably improved by the addition of artesunate to AQ or by use of SP; adequate clinical and parasitological response being 72% for AQ/AS and 92% for SP. The combination of AS/AQ substantially reduced the odds of treatment failure relative to AQ monotherapy by day 42 [odds ratio (OR) = 0.03, 95% confidence interval (CI) 0.01-0.1] in addition to reducing the proportion of patients with gametocytes throughout the 42-day period. Gametocyte carriage rate was only marginally higher in the SP than in the CQ- and AQ-treated groups. CONCLUSION: The therapeutic and parasitological cure rates with AS/AQ were inadequate, and the criteria for deploying ACT - namely to prevent further selection of drug resistance from a position of low frequency - was not met in the region. An alternative drug combination to AQ/AS is required for Afghanistan.     

Low efficacy of amodiaquine or chloroquine plus sulfadoxine-pyrimethamine against Plasmodium falciparum and P. vivax malaria in Papua New Guinea

Because of increasing resistance to 4-aminoquinolines in Papua New Guinea, combination therapy of amodiaquine (AQ) or chloroquine (CQ) plus sulfadoxine-pyrimethamine (SP) was introduced as first-line treatment against uncomplicated malaria in 2000. The purpose of this study was to monitor in vivo efficacy of the current standard combination therapy against Plasmodium falciparum and P. vivax malaria. Studies were conducted between 2003 and 2005 in the Simbu, East Sepik, and Madang Provinces in Papua New Guinea according to the revised protocol of the World Health Organization (WHO) for assessment of antimalarial drug efficacy. Children between six months and seven years of age with clinically overt and parasitologically confirmed P. falciparum or P. vivax malaria were treated according to the new policy guidelines (i.e., AQ plus SP given to patients weighing < 14 kg and CQ plus SP given to patients weighing < 14 kg). Children were monitored up to day 28 and classified according to clinical and parasitological outcome as adequate clinical and parasitological response (ACPR), early treatment failure (ETF), late clinical failure (LCF), or late parasitological failure (LPF). For P. falciparum malaria, polymerase chain reaction (PCR)-corrected treatment failure rates up to day 28 ranged between 10.3% and 28.8% for AQ plus SP and between 5.6% and 28.6% for CQ plus SP, depending on the region and the year of assessment. Overall treatment failure rate with AQ or CQ plus SP for P. vivax malaria was 12%. Our results suggest that the current first-line treatment in Papua New Guinea is not sufficiently effective. According to the new WHO guidelines for the treatment of malaria, a rate of parasitological resistance greater than 10% in the two dominant malaria species in the country justifies a change in treatment policy.     

The efficacy of combined mefloquine-artesunate versus mefloquine-primaquine on subsequent development of Plasmodium falciparum gametocytemia

An open randomized controlled study of mefloquine-artesunate and mefloquine-primaquine for the treatment of uncomplicated Plasmodium falciparum malaria was carried out in Kanchanaburi in the Saiyok District in western Thailand. Weekly parasite counts from thick and thin blood films were done for six weeks. The gametocyte carriage rate was calculated and compared between the two treatment groups. Gametocytes on presentation, recrudescent infection, and reinfection were the significant factors associated with subsequent development of gametocytemia. It is the increased propensity of recrudescent infections to produce gametocytes that drives drug resistance. The results of this study confirmed that the complete eradication of a sexual forms of P. falciparum by effective antimalarial treatment, but not by combination treatment with primaquine, is the most effective means to prevent subsequent gametocytemia.     

Efficacy of artesunate plus amodiaquine, artesunate plus sulfadoxine-pyrimethamine, and chloroquine plus sulfadoxine-pyrimethamine in patients with uncomplicated Plasmodium falciparum in the Comoros Union

Health policy makers in Comoros Union have considered a policy change recommending combination treatment to control malaria. We evaluated the efficacy of three antimalarial drug combinations, taken orally, to enable the authorities to make an evidence-based choice. The study was carried out in patients of 2-70 years old in Moroni, Moheli and Anjouan in 2003. We enrolled 168 patients with uncomplicated malaria from 1097 outpatients screened at the health centres. One hundred and fifty-eight patients, of whom half were under five years old, (mean age=11.1+/-13.9 years), were followed up for 14 days. According to PCR adjusted outcome, the therapeutic efficacy of artesunate+amodiaquine (AS+AQ) (n=54) and artesunate+sulfadoxine-pyrimethamine (AS+SP) (n=53) was 100%, whereas that of chloroquine+sulfadoxine-pyrimethamine (CQ+SP) was 98% (50/51). The key difference between these treatments was the higher parasite clearance rate on Day 2 obtained with artesunate-containing combinations (P<0.001). These results provide a baseline for monitoring changes in the susceptibility of Plasmodium falciparum to artesunate+amodiaquine and artesunate+sulfadoxine-pyrimethamine (ACTs) in the Comoros Union. Health policy changes involving the replacement of chloroquine in the Indian Ocean subregion are discussed.     

Role of Plasmodium falciparum chloroquine resistance transporter and multidrug resistance 1 genes on in vitro chloroquine resistance in isolates of Plasmodium falciparum from Thailand

Resistance to chloroquine is a public health problem worldwide. Polymorphisms of the Plasmodium falciparum chloroquine resistance transporter (pfcrt) and P. falciparum multidrug resistance 1 (pfmdr1) genes have been linked to chloroquine resistance. Although the K76T mutation in the pfcrt gene has been shown to be a key determinant in chloroquine resistance, evidence suggests that the pfmdr1 gene could modulate the level of chloroquine resistance. However, few studies of field isolates could identify the interactive role of these two genes in chloroquine resistance. Thus, we evaluated the influence of pfcrt and pfmdr1 polymorphisms on in vitro chloroquine sensitivity in 89 adapted isolates of P. falciparum from Thailand. We found that 87 of 89 isolates contained the CVIET haplotype of the pfcrt gene. Two additional mutations in the pfcrt gene were identified, i.e., K6Q and H97L. For the pfmdr1 polymorphisms, the 184F allele was common in the parasites isolated along the Thailand-Cambodia border, and those isolated along the Thailand-Myanmar border contained higher copy numbers. Our results indicate that the additional mutations, in particular H97L in the pfcrt gene and Y184F in the pfmdr1 gene and its copy number, influence the level of chloroquine resistance.     

Sensitivity status of Plasmodium falciparum to chloroquine, amodiaquine, quinine, mefloquine and sulfadoxine/pyrimethamine in a tribal population of District Sundargarh, Orissa.

In a malaria-endemic area of Orissa, wherein chloroquine has been in use for over thirty years, 58.3% (14/24) P. falciparum cases did not respond to single dose chloroquine (10 mg base/kg) in in-vivo test. With standard dose (25 mg base/kg) 31.2% cases (10/32) showed resistance, i.e. at RI (15.6%), RII (9.4%) and RIII (6.2%) levels. Standard dose was superior in response to the single dose therapy [p < 0.05; chi 2 (df 1) = 4.11]. Out of eight isolates tested in vitro, two showed resistance to chloroquine, five to sulfadoxine/pyrimethamine (SP) but all were sensitive to amodiaquine, quinine and mefloquine. Whereas the standard dose of chloroquine would be a better option in general, in resistant cases, SP, quinine and mefloquine offer an alternative drug choice. The implications of drug resistance in a malaria-control programme and the need to revise drug policy in India are discussed.     

恶性疟原虫氯喹抗药性基因pfcrt研究进展

自从1959年第1例抗氯喹的恶性疟病人出现以来,恶性疟原虫氯喹抗药性(chloroquineresistance,CQR)已经遍及所有恶性疟流行地区,在东南亚地区CQR引发了更为严重的公共卫生问题,在我国云南、海南等省也有CQR恶性疟的流行。因此,对恶性疟原虫氯喹抗药性的研究已经成为当前疟疾防治研究中的一个重点。随着恶性疟原虫基因组研究的进展,抗药性基因已经成为CQR研究的热点。国外研究