Comparison of two mefloquine regimens for treatment of Plasmodium falciparum malaria on the northeastern Thai-Cambodian border

Molecular insights into artemisinin resistance in Plasmodium falciparum: An updated review

Malaria still poses a major burden on human health around the world, especially in endemic areas. Plasmodium resistance to several antimalarial drugs has been one of the major hindrances in control of malaria. Thus, the World Health Organization recommended artemisinin-based combination therapy (ACT) as a front-line treatment for malaria. The emergence of parasites resistant to artemisinin, along with resistant to ACT partner drugs, has led to ACT treatment failure. The artemisinin resistance is mostly related to the mutations in the propeller domain of the kelch13 (k13) gene that encodes protein Kelch13 (K13). The K13 protein has an important role in parasite reaction to oxidative stress. The most widely spread mutation in K13, with the highest degree of resistance, is a C580Y mutation. Other mutations, which are already identified as markers of artemisinin resistance, are R539T, I543T, and Y493H. The objective of this review is to provide current molecular insights into artemisinin resistance in Plasmodium falciparum. The trending use of artemisinin beyond its antimalarial effect is described. Immediate challenges and future research directions are discussed. Better understanding of the molecular mechanisms underlying artemisinin resistance will accelerate implementation of scientific findings to solve problems with malarial infection.

Delivering infectious disease interventions to women and children in conflict settings: a systematic reviefw

BACKGROUND

Conflict has played a role in the large-scale deterioration of health systems in low-income and middle-income countries (LMICs) and increased risk of infections and outbreaks. This systematic review aimed to synthesise the literature on mechanisms of delivery for a range of infectious disease-related interventions provided to conflict-affected women, children and adolescents.

METHODS

We searched Medline, Embase, CINAHL and PsychINFO databases for literature published in English from January 1990 to March 2018. Eligible publications reported on conflict-affected neonates, children, adolescents or women in LMICs who received an infectious disease intervention. We extracted and synthesised information on delivery characteristics, including delivery site and personnel involved, as well as barriers and facilitators, and we tabulated reported intervention coverage and effectiveness data.

RESULTS

A majority of the 194 eligible publications reported on intervention delivery in sub-Saharan Africa. Vaccines for measles and polio were the most commonly reported interventions, followed by malaria treatment. Over two-thirds of reported interventions were delivered in camp settings for displaced families. The use of clinics as a delivery site was reported across all intervention types, but outreach and community-based delivery were also reported for many interventions. Key barriers to service delivery included restricted access to target populations; conversely, adopting social mobilisation strategies and collaborating with community figures were reported as facilitating intervention delivery. Few publications reported on intervention coverage, mostly reporting variable coverage for vaccines, and fewer reported on intervention effectiveness, mostly for malaria treatment regimens.

CONCLUSIONS

Despite an increased focus on health outcomes in humanitarian crises, our review highlights important gaps in the literature on intervention delivery among specific subpopulations and geographies. This indicates a need for more rigorous research and reporting on effective strategies for delivering infectious disease interventions in different conflict contexts.

PROSPERO REGISTRATION NUMBER

CRD42019125221.

Effectiveness and safety of 3 and 5 day courses of artemether-lumefantrine for the treatment of uncomplicated falciparum malaria in an area of emerging artemisinin resistance in Myanmar

BACKGROUND

Artemisinin resistance in Plasmodium falciparum has emerged and spread in Southeast Asia. In areas where resistance is established longer courses of artemisinin-based combination therapy have improved cure rates.

METHODS

The standard 3-day course of artemether-lumefantrine (AL) was compared with an extended 5-day regimen for the treatment of uncomplicated falciparum malaria in Kayin state in South-East Myanmar, an area of emerging artemisinin resistance. Late parasite clearance dynamics were described by microscopy and quantitative ultra-sensitive PCR. Patients were followed up for 42 days.

RESULTS

Of 154 patients recruited (105 adults and 49 children < 14 years) 78 were randomized to 3 days and 76 to 5 days AL. Mutations in the P. falciparum kelch13 propeller gene (k13) were found in 46% (70/152) of infections, with F446I the most prevalent propeller mutation (29%; 20/70). Both regimens were well-tolerated. Parasite clearance profiles were biphasic with a slower submicroscopic phase which was similar in k13 wild-type and mutant infections. The cure rates were 100% (70/70) and 97% (68/70) in the 3- and 5-day arms respectively. Genotyping of the two recurrences was unsuccessful.

CONCLUSION

Despite a high prevalence of k13 mutations, the current first-line treatment, AL, was still highly effective in this area of South-East Myanmar. The extended 5 day regimen was very well tolerated, and would be an option to prolong the useful therapeutic life of AL. Trial registration NCT02020330. Registered 24 December 2013, https://clinicaltrials.gov/NCT02020330.

Tools for surveillance of anti-malarial drug resistance: an assessment of the current landscape

To limit the spread and impact of anti-malarial drug resistance and react accordingly, surveillance systems able to detect and track in real-time its emergence and spread need to be strengthened or in some places established. Currently, surveillance of anti-malarial drug resistance is done by any of three approaches: (1) in vivo studies to assess the efficacy of drugs in patients; (2) in vitro/ex vivo studies to evaluate parasite susceptibility to the drugs; and/or (3) molecular assays to detect validated gene mutations and/or gene copy number changes that are associated with drug resistance. These methods are complementary, as they evaluate different aspects of resistance; however, standardization of methods, especially for in vitro/ex vivo and molecular techniques, is lacking. The World Health Organization has developed a standard protocol for evaluating the efficacy of anti-malarial drugs, which is used by National Malaria Control Programmes to conduct their therapeutic efficacy studies. Regional networks, such as the East African Network for Monitoring Antimalarial Treatment and the Amazon Network for the Surveillance of Antimalarial Drug Resistance, have been set up to strengthen regional capacities for monitoring anti-malarial drug resistance. The Worldwide Antimalarial Resistance Network has been established to collate and provide global spatial and temporal trends information on the efficacy of anti-malarial drugs and resistance. While exchange of information across endemic countries is essential for monitoring anti-malarial resistance, sustainable funding for the surveillance and networking activities remains challenging. The technology landscape for molecular assays is progressing quite rapidly, and easy-to-use and affordable new techniques are becoming available. They also offer the advantage of high throughput analysis from a simple blood spots obtained from a finger prick. New technologies combined with the strengthening of national reference laboratories in malaria-endemic countries through standardized protocols and training plus the availability of a proficiency testing programme, would contribute to the improvement and sustainability of anti-malarial resistance surveillance networks worldwide.

Antimalarial Drug Resistance: A Threat to Malaria Elimination

Increasing antimalarial drug resistance once again threatens effective antimalarial drug treatment, malaria control, and elimination. Artemisinin combination therapies (ACTs) are first-line treatment for uncomplicated falciparum malaria in all endemic countries, yet partial resistance to artemisinins has emerged in the Greater Mekong Subregion. Concomitant emergence of partner drug resistance is now causing high ACT treatment failure rates in several areas. Genetic markers for artemisinin resistance and several of the partner drugs have been established, greatly facilitating surveillance. Single point mutations in the gene coding for the Kelch propeller domain of the K13 protein strongly correlate with artemisinin resistance. Novel regimens and strategies using existing antimalarial drugs will be needed until novel compounds can be deployed. Elimination of artemisinin resistance will imply elimination of all falciparum malaria from the same areas. In vivax malaria, chloroquine resistance is an increasing problem.

Adverse effects of mefloquine for the treatment of uncomplicated malaria in Thailand: A pooled analysis of 19, 850 individual patients

Mefloquine (MQ) has been used for the treatment of malaria since the mid-1980s, first as monotherapy or as fixed combination with sulfadoxine-pyrimethamine (MSP) and since the mid-1990s in combination with artesunate. There is a renewed interested in MQ as part of a triple therapy for the treatment of multi-drug resistance P. falciparum malaria. The widespread use of MQ beyond south-East Asia has been constrained by reports of poor tolerability. Here we present the side effect profile of MQ for the treatment of uncomplicated malaria on the Thai-Myanmar/Cambodia borders. In total 19,850 patients received seven different regimens containing either 15 or 24-25 mg/kg of MQ, the latter given either as a single dose, or split over two or three days. The analysis focused on (predominantly) gastrointestinal and neuropsychiatric events as compared to the new fixed dose combination of MQ plus artesunate given as equal doses of 8 mg/kg MQ per day over three days. Gastrointestinal side effects were dose-dependent and associated with the severity of malaria symptoms. Serious neuropsychiatric side effects associated with MQ use were rare: for a single 25 mg/kg dose it was 11.9 per 10,000 treatments (95% confidence interval, CI, 4-285) vs. 7.8 (3-15) for the 15 mg/kg dose. The risk with 25 mg/kg was much higher when it was given as repeat dosing in patients who had failed treatment with 15 mg/kg MQ in the preceding month; (RR 6.57 (95% CI 1.33 to 32.4), p = 0.0077). MQ was best tolerated as 15 mg/kg or as 24 mg/kg when given over three days in combination with artesunate. We conclude that the tolerance of a single dose of MQ in the treatment of uncomplicated malaria is moderate, but can be improved by administering it as a split dose over three days.

Plasmodium falciparum Resistance to Artemisinin Derivatives and Piperaquine: A Major Challenge for Malaria Elimination in Cambodia

Artemisinin-based combination therapies (ACTs) are the cornerstone of current strategies for fighting malaria. Over the last decade, ACTs have played a major role in decreasing malaria burden. However, this progress is being jeopardized by the emergence of artemisinin-resistant Plasmodium falciparum parasites. Artemisinin resistance was first detected in western Cambodia in 2008 and has since been observed in neighboring countries in southeast Asia. The problem of antimalarial drug resistance has recently worsened in Cambodia, with reports of parasites resistant to piperaquine, the latest generation of partner drug used in combination with dihydroartemisinin, leading to worrying rates of clinical treatment failure. The monitoring and the comprehension of both types of resistance are crucial to prevent the spread of multidrug-resistant parasites outside southeast Asia, and particularly to Africa, where the public health consequences would be catastrophic. To this end, new tools are required for studying the biological and molecular mechanisms underlying resistance to antimalarial drugs and for monitoring the geographic distribution of the resistant parasites. In this review, we detail the major advances in our understanding of resistance to artemisinin and piperaquine and define the challenges that the malaria community will have to face in the coming years.

Focused Screening and Treatment (FSAT): a PCR-based strategy to detect malaria parasite carriers and contain drug resistant P. falciparum, Pailin, Cambodia

Recent studies have shown that Plasmodium falciparum malaria parasites in Pailin province, along the border between Thailand and Cambodia, have become resistant to artemisinin derivatives. To better define the epidemiology of P. falciparum populations and to assess the risk of the possible spread of these parasites outside Pailin, a new epidemiological tool named “Focused Screening and Treatment” (FSAT), based on active molecular detection of asymptomatic parasite carriers was introduced in 2010. Cross-sectional malariometric surveys using PCR were carried out in 20 out of 109 villages in Pailin province. Individuals detected as P. falciparum carriers were treated with atovaquone-proguanil combination plus a single dose of primaquine if the patient was non-G6PD deficient. Interviews were conducted to elicit history of cross-border travel that might contribute to the spread of artemisinin-resistant parasites. After directly observed treatment, patients were followed up and re-examined on day 7 and day 28. Among 6931 individuals screened, prevalence of P. falciparum carriers was less than 1%, of whom 96% were asymptomatic. Only 1.6% of the individuals had a travel history or plans to go outside Cambodia, with none of those tested being positive for P. falciparum. Retrospective analysis, using 2010 routine surveillance data, showed significant differences in the prevalence of asymptomatic carriers discovered by FSAT between villages classified as “high risk” and “low risk” based on malaria incidence data. All positive individuals treated and followed-up until day 28 were cured. No mutant-type allele related to atovaquone resistance was found. FSAT is a potentially useful tool to detect, treat and track clusters of asymptomatic carriers of P. falciparum along with providing valuable epidemiological information regarding cross-border movements of potential malaria parasite carriers and parasite gene flow.

Use of mefloquine in children - a review of dosage, pharmacokinetics and tolerability data

BACKGROUND

Use of anti-malarial medication in children is hampered by a paucity of dosage, pharmacokinetic and tolerability data.

METHODS

Data on the use of mefloquine in children, particularly in young children weighing less than 20 kg, were reviewed using PubMed literature and reports on file.

RESULTS

Chemoprophylaxis data: Two studies with a total of 170 children were found. A simulated mefloquine plasma profile showed that doses to achieve protective chemoprophylaxis blood concentration of mefloquine of approximately 620 ng/mL (or 1.67 μmol/L) in children should be at least 5 mg/kg. This simulated plasma profile in children corresponds to that seen in adult travellers using a weekly prophylaxis dose of 250 mg. This reinforces current practice of using weight-based dosage for children. Clearance per body weight is higher in older children. For children who travel to malaria risk areas tablets can be broken and crushed as required. It is necessary to disguise the bitter taste of the drug. Treatment data: Mefloquine treatment (alone or in combination) data are available for more than 6000 children of all age and weight categories. The stereoselectivity and pharmacokinetic profile of mefloquine in children is similar to that observed in adults. There is higher clearance in older children (aged 5-12 years) compared to younger children (aged 6-24 months). Mefloquine treatment is well tolerated in infants (5-12 kg) but vomiting is a problem at high doses. This led to the use of a "split dose" regimen with 15 mg/kg initially, followed 12 hours later by 10 mg/kg. Mefloquine 125 mg has been used as intermittent preventive treatment (IPT) and was found to be efficacious in reducing episodes of malaria in a moderate-transmission setting but vomiting was a problem in 8% of children aged 2-11 months. Mefloquine is also used as a component of artemisinin combination therapy (ACT) in small children. The combination artesunate plus mefloquine is a WHO approved first-line treatment for uncomplicated malaria in Africa.

CONCLUSION

Currently available data provide a scientific basis for the use of mefloquine in small children in the chemoprophylaxis setting and as a part of treatment regimens for children living in endemic areas.

Mefloquine adverse effects with atypical facial lesions in an overweight patient

BACKGROUND

The recommended dosage of mefloquine to treat Plasmodium falciparum infection is 25 mg/kg, with no recommendation for dosage exceeding 1500 mg. We describe an original case of adverse reaction to mefloquine in an overweight patient.

METHOD

Case report.

RESULTS

A 32-year-old woman weighing 139 kg presented with uncomplicated P. falciparum infection after returning from Cameroon. She received 3250 mg of mefloquine (i.e. 23 mg/kg) administered in four doses. On day 2, she developed neuropsychiatric disorders and facial lesions. Nasal mucocutaneous vesicles and bullae, depressive mood, mild thrombocytopenia and hepatic cytolysis were evidenced. Parasitemia was negative. Recovery was complete on day 17. High mefloquine serum levels were measured (8.030 mg/L on day 3, 6.880 mg/L on day 8, and 3.370 mg/L on day 17).

CONCLUSIONS

The causal relationship between mefloquine and the occurrence of these adverse effects is probable. However, as no viral or bacteriological investigations were performed, the drug responsibility remains uncertain. Mefloquine-induced bullous and facial lesions reversible upon drug withdrawal have already been described. The associated neuropsychiatric symptoms were strongly suggestive of mefloquine adverse effects, as such events are more frequently observed in cases of overdosage. Our case emphasizes the difficulties of dosage adaptation in overweight patients.

Efficacy and safety of the six-dose regimen of artemether-lumefantrine for treatment of uncomplicated Plasmodium falciparum malaria in adolescents and adults: a pooled analysis of individual patient data from randomized clinical trials

To demonstrate the superiority of the six-dose over the four-dose regimen of artemether-lumefantrine (co-artemether, Coartem) in patients >12 years, data from 11 randomized clinical trials were pooled and analyzed. A total of 1368 patients with uncomplicated Plasmodium falciparum malaria (six-dose: 598; four-dose: 770) were included in the analysis, together with 717 patients treated with comparators. Analysis of the 28-day cure rate based on the ITT and evaluable populations yielded corrected cure rates for the six-dose regimen of 87% and 97% compared with 74% and 87%, respectively, with the four-dose regimen (P<0.0001, for both comparisons). For mefloquine/artesunate, the most frequently used comparator, cure rates were 87% and 99%, respectively. The six-dose regimen was well tolerated and not markedly different to the four-dose regimen. The main finding of our analysis is that the six-dose regimen of co-artemether is more effective than the four-dose regimen in adolescents and adults without compromising safety.

Surveillance of the efficacy of artesunate and mefloquine combination for the treatment of uncomplicated falciparum malaria in Cambodia

Artesunate and mefloquine combination treatment has been used since 2000 in Cambodia as the first-line drug for the treatment of uncomplicated falciparum malaria. In order to assess its efficacy and safety, the national malaria control programme conducted 14 therapeutic efficacy studies with the drug combination between 2001 and 2004 at nine sites. In 2001 and 2002, co-blister packs of artesunate and mefloquine were used, whereas in 2003 and 2004, drugs were given individually from a bulk pack at a total dose of 12 mg/kg of artesunate and 25 mg/kg of mefloquine over 3 days. A total of 1025 patients were enrolled over the 4 years and 977 were follow-up during the period of 28 days. The PCR-corrected cure rates ranged from 85.7% to 100% with an overall cure rate of 95.8% (920/960). The studies in 2002 showed also that co-blister packs used on the basis of age and not on the basis of weight could lead to underdosed regimens but without any detectable effect on the treatment outcome. The follow-up period was extended from 28 to 42 days in three sites in 2004. A total of 219 among 255 were follow-up until day 42. The cure rate decreased but not significantly from 90.1% (73/81) with 28 days follow-up to 79.3% (46/58) with 42 days follow-up in Pailin, whereas the cure rate remained at 100% in the two other sites. Side effects were common, especially dizziness, but were mild and transient and patients recovered without any medical intervention.

Psychosis with paranoid delusions after a therapeutic dose of mefloquine: a case report

Background

Convenient once-a-week dosing has made mefloquine a popular choice as malaria prophylaxis for travel to countries with chloroquine-resistant malaria. However, the increased use of mefloquine over the past decade has resulted in reports of rare, but severe, neuropsychiatric adverse reactions, such as anxiety, depression, hallucinations and psychosis. A direct causality between mefloquine and severe reactions among travelers has been partly confounded by factors associated with foreign travel and, in the case of therapeutic doses of mefloquine, the central nervous system manifestations of Plasmodium infection itself. The present case provides a unique natural history of mefloquine-induced neuropsychiatric toxicity and revisits its dose-dependent nature.

Case presentation

This report describes an acute exacerbation of neuropsychiatric symptoms after an unwarranted therapeutic dose (1250 mg) of mefloquine in a 37-year-old male previously on a once-a-week prophylactic regimen. Neuropsychiatric symptoms began as dizziness and insomnia of several days duration, which was followed by one week of escalating anxiety and subtle alterations in behaviour. The patient's anxiety culminated into a panic episode with profound sympathetic activation. One week later, he was hospitalized after developing frank psychosis with psychomotor agitation and paranoid delusions. His psychosis remitted with low-dose quetiapine.

Conclusion

This report suggests that an overt mefloquine-induced psychosis can be preceded by a prodromal phase of moderate symptoms such as dizziness, insomnia, and generalized anxiety. It is important that physicians advise patients taking mefloquine prophylaxis and their relatives to recognize such symptoms, especially when they are accompanied by abrupt, but subtle, changes in behaviour. Patients with a history of psychiatric illness, however minor, may be at increased risk for a mefloquine-induced neuropsychiatric toxicity. Physicians must explicitly caution patients not to self-medicate with a therapeutic course of mefloquine when a malaria diagnosis has not been confirmed.

Mefloquine Is Highly Efficacious against Chloroquine-Resistant Plasmodium vivax Malaria and Plasmodium falciparum Malaria in Papua, Indonesia

BACKGROUND

During the period of 1996-1999, we prospectively monitored 243 Javanese adults and children after arriving in Papua, Indonesia, and microscopically documented each new case of malaria by active surveillance.

METHODS

In a randomized, open-label, comparative malaria treatment trial, 72 adults and 50 children received chloroquine for each incident case of malaria, and 74 adults and 47 children received mefloquine.

RESULTS

Among 975 primary treatment courses, the cumulative 28-day curative efficacies were 26% and 82% for chloroquine against Plasmodium falciparum malaria and Plasmodium vivax malaria, respectively. Mefloquine cure rates were far superior (96% against P. falciparum malaria and 99.6% against P. vivax malaria).

CONCLUSIONS

Mefloquine is a useful alternative treatment for P. vivax malaria and P. falciparum malaria in areas such as Papua, where chloroquine is still recommended as the first-line therapeutic agent.

Efficacies of mefloquine alone and of artesunate followed by mefloquine, for the treatment of uncomplicated, Plasmodium falciparum malaria in eastern Sudan

In late 2003, the efficacies of mefloquine monotherapy and of an artesunate-mefloquine combination, for the oral treatment of uncomplicated, Plasmodium falciparum malaria, were investigated and compared in New Halfa, in eastern Sudan. Of the patients who completed the 28 days of follow-up, 40 were treated only with single-dose mefloquine (at a dose of 25 mg/kg), and 38 with artesunate (at 4 mg/kg. day) for 3 days followed by single-dose mefloquine (at 15 mg/kg), given on the third day. Compared with those given the combination, the patients given mefloquine alone were more likely to suffer nausea, vomiting and dizziness (25.0% v. 2.6%; P=0.005) and to be found gametocytaemic (12.5% v. 0%; P=0.02) after treatment, and more likely to be found febrile (i.e. with a temperature >37.5 degrees C) on day 2 (25.0% v. 2.6%; P=0.005), although no patients were found febrile on day 3. Six of the patients--three (7.5%) of those given mefloquine only and three (7.9%) of those given the combination (P>0.05)--appeared to be treatment failures. Parasite genotyping indicated, however, that, although five of these six patients had true recrudescences, one (who had been treated with the combination) had been re-infected during the follow-up. The true frequencies of cure were therefore 92.5% after mefloquine alone and 94.7% after the combination (P>0.05). Thus, although the treatments appeared equally effective in clearing parasitaemias, the combination was better at clearing gametocytaemias and was less likely to cause adverse side-effects. It remains unclear why mefloquine given alone was almost 10-fold more likely to trigger adverse effects than treatment with a combination that contained the same drug. This may be a reflection of the different mefloquine doses and, for the patients given the combination, of the use of artesunate before the mefloquine treatment.

Mechanisms of resistance of malaria parasites to antifolates

Antifolate antimalarial drugs interfere with folate metabolism, a pathway essential to malaria parasite survival. This class of drugs includes effective causal prophylactic and therapeutic agents, some of which act synergistically when used in combination. Unfortunately, the antifolates have proven susceptible to resistance in the malaria parasite. Resistance is caused by point mutations in dihydrofolate reductase and dihydropteroate synthase, the two key enzymes in the folate biosynthetic pathway that are targeted by the antifolates. Resistance to these drugs arises relatively rapidly in response to drug pressure and is now common worldwide. Nevertheless, antifolate drugs remain first-line agents in several sub-Saharan African countries where chloroquine resistance is widespread, at least partially because they remain the only affordable, effective alternative. New antifolate combinations that are more effective against resistant parasites are being developed and in one case, recently introduced into use. Combining these antifolates with drugs that act on different targets in the parasite should greatly enhance their effectiveness as well as deter the development of resistance. Molecular epidemiological techniques for monitoring parasite drug resistance may contribute to development of strategies for prolonging the useful therapeutic life of this important class of drugs.

Mefloquine resistance in Plasmodium falciparum

Mefloquine resistance in Plasmodium falciparum, the most dangerous of the four pathogenic malaria parasites of humans, is established in several endemic regions of the world. After a promising start, resistance has developed to disturbing extents in some areas, whereas in many regions it remains an effective drug. In this article, Frank Mockenhaupt reviews the factors that are likely to influence the development of mefloquine resistance, its possible mechanism and its geographical spread.

In vivo assessment of drug efficacy against Plasmodium falciparum malaria: duration of follow-up

To determine the optimum duration of follow-up for the assessment of drug efficacy against Plasmodium falciparum malaria, 96 trial arms from randomized controlled trials (RCTs) with follow-up of 28 days or longer that were conducted between 1990 and 2003 were analyzed. These trials enrolled 13,772 patients, and participating patients comprised 23% of all patients enrolled in RCTs over the past 40 years; 61 (64%) trial arms were conducted in areas where the rate of malaria transmission was low, and 58 (50%) trial arms were supported by parasite genotyping to distinguish true recrudescences from reinfections. The median overall failure rate reported was 10% (range, 0 to 47%). The widely used day 14 assessment had a sensitivity of between 0 and 37% in identifying treatment failures and had no predictive value. Assessment at day 28 had a sensitivity of 66% overall (28 to 100% in individual trials) but could be used to predict the true failure rate if either parasite genotyping was performed (r(2) = 0.94) or if the entomological inoculation rate was known. In the assessment of drug efficacy against falciparum malaria, 28 days should be the minimum period of follow-up.

Randomised efficacy and safety study of two 3-day artesunate rectal capsule/mefloquine regimens versus artesunate alone for uncomplicated malaria in Ecuadorian children

The combination of artesunate and mefloquine is one of the most effective treatments against multidrug-resistant falciparum malaria. Experience in children is however limited. The objective of this study was to compare the efficacy and safety of two artesunate/mefloquine combinations with artesunate monotherapy in Ecuadorian children. A total of 150 children with an age between 2 and 12 years, confirmed to have uncomplicated falciparum malaria, were randomly selected and divided in three treatment groups of 50 patients each. Group 1 received 50 mg rectal capsules alone (40 mg/kg total dose) administered over 6 days. Group 2 received 50 mg rectal capsules (30 mg/kg total dose) for 3 days combined with mefloquine (20 mg/kg total dose) on day 1. Group 3 was treated with 50 mg rectal capsules (30 mg/kg total dose) for 3 days, combined with mefloquine on days 1 and 3 (15-17 mg/kg total dose). Patients were continuously followed up and controlled by clinical and laboratory examinations for 7 days as well as on days 14, 21 and 28. An additional parasite examination was performed at 2 months following therapy. Clearance of parasitaemia was comparable between treatment groups. These were 9.2, 9.2 and 8.3 h for Groups 1, 2 and 3, respectively. Cure rates at day 28 were 76, 96 and 94% and after 2 months 60, 88 and 80%, respectively. There were no adverse events (AEs) reported during the study. Vital signs and laboratory examinations revealed no changes of clinical relevance. It can be concluded that the combination of artesunate rectal capsules with mefloquine is effective and safe. Starting concomitant administration already on day 1 is well tolerated. This combination significantly reduces the incidence of recrudescence compared to artesunate monotherapy. Comparing the two tested artesunate/mefloquine regimens, a total mefloquine dose of 20 mg/kg seems to be more effective compared to a total dose of 15-17 mg/kg. Further studies seem to be warranted.

Therapeutic efficacy of chloroquine plus sulphadoxine/ pyrimethamine compared with monotherapy with either chloroquine or sulphadoxine/pyrimethamine in uncomplicated Plasmodium falciparum malaria in Laos

In a southern border province of Lao PDR, we compared the efficacy of antimalarial drug combinations in patients aged >or=1 year with uncomplicated Plasmodium falciparum malaria: monotherapy with either mefloquine (MQ), chloroquine (CQ), or sulphadoxine/pyrimethamine (SP) vs. the combination of both CQ and SP. Follow-up time was 14 days. Of 265 P. falciparum positive patients, 119 were enrolled in the drug trial. Significantly more patients treated with CQ than with SP developed early or late treatment failure [44.8%vs. 17.9%, relative risk (RR) = 2.51, 95% CI 1.03-6.12]. In the SP group, 82.1% were sensitive and 17.9% were treatment failures. The combination treatment CQ plus SP resulted in 83.3% sensitivity and 16.7% treatment failures. Combination treatment has no advantage over monotherapy with SP (RR = 1.01, 95% CI 0.8-1.3). All patients who received MQ for treatment (total dose 25 mg/kg) were cured within the 14 days of follow-up. The findings of this study suggest that use of CQ as first-line treatment of uncomplicated malaria in the Lao PDR has to be reconsidered. The combination of both CQ and SP has been discussed as a cost-effective alternative treatment, but in our patient population achieved no better results than single therapy with SP.

A randomized, double-blind study on the efficacy and safety of a practical three-day regimen with artesunate and mefloquine for the treatment of uncomplicated Plasmodium falciparum malaria in Africa

A randomized, double-blind, parallel-group study in 104 hospitalized patients with acute, uncomplicated Plasmodium falciparum malaria was performed in West and Central Africa from March to July 2001. Patients were randomized to receive simultaneous dosing (artesunate 200 mg/d plus mefloquine 250 mg/d from the first to the third day [investigational group]) or sequential dosing (artesunate 200 mg/d for 3 d plus mefloquine 250 mg on the second and 500 mg on the third day [reference group]). Patients were followed-up for 28 d, and clinical and parasitological outcomes were assessed. The 14-d cure rate was 100% in the investigational group and 98% in the reference group with no recrudescence until day 28. Mean times to fever and parasite clearance were similar between the 2 groups (32 h vs. 26 h and 45 h vs. 48 h) and tolerability was good in both groups. The number of patients with vomiting was statistically significantly lower in the investigational group compared to the reference group (3.8% vs. 19.2%, P = 0.014). A 3-d once-daily co-administration of artesunate and mefloquine starting on day one offers a practical dosing regimen, which is highly effective and well tolerated in patients with uncomplicated P. falciparum malaria.

The assessment of antimalarial drug efficacy

Antimalarial drug efficacy in uncomplicated malaria should be assessed parasitologically in large, community-based trials, enrolling the age groups most affected by clinical disease. For rapidly eliminated drugs, a 28-day follow-up is needed, but, for slowly eliminated drugs, up to nine weeks could be required to document all recrudescences, and, when possible, the drug levels should also be measured. The WHO 14-day assessments are neither sensitive nor specific. In tropical Plasmodium vivax and Plasmodium ovale infections treated with chloroquine, the first relapse is usually suppressed by residual drug levels. A relapse cannot be distinguished confidently from a recrudescence. Host immunity is a major contributor to the therapeutic response, and can make failing drugs appear effective.

Adverse effects of the antimalaria drug, mefloquine: due to primary liver damage with secondary thyroid involvement?

BACKGROUND

Mefloquine is a clinically important antimalaria drug, which is often not well tolerated. We critically reviewed 516 published case reports of mefloquine adverse effects, to clarify the phenomenology of the harms associated with mefloquine, and to make recommendations for safer prescribing.

PRESENTATION

We postulate that many of the adverse effects of mefloquine are a post-hepatic syndrome caused by primary liver damage. In some users we believe that symptomatic thyroid disturbance occurs, either independently or as a secondary consequence of the hepatocellular injury. The mefloquine syndrome presents in a variety of ways including headache, gastrointestinal disturbances, nervousness, fatigue, disorders of sleep, mood, memory and concentration, and occasionally frank psychosis. Previous liver or thyroid disease, and concurrent insults to the liver (such as from alcohol, dehydration, an oral contraceptive pill, recreational drugs, and other liver-damaging drugs) may be related to the development of severe or prolonged adverse reactions to mefloquine.

IMPLICATIONS

We believe that people with active liver or thyroid disease should not take mefloquine, whereas those with fully resolved neuropsychiatric illness may do so safely. Mefloquine users should avoid alcohol, recreational drugs, hormonal contraception and co-medications known to cause liver damage or thyroid damage. With these caveats, we believe that mefloquine may be safely prescribed in pregnancy, and also to occupational groups who carry out safety-critical tasks.

TESTING

Mefloquine's adverse effects need to be investigated through a multicentre cohort study, with small controlled studies testing specific elements of the hypothesis.

Human malaria in immunocompromised mice: new in vivo model for chemotherapy studies

We have recently designed a new Plasmodium falciparum mouse model and documented its potential for the study of immune effector mechanisms. In order to determine its value for drug studies, we evaluated its response to existing antimalarial drugs compared to that observed in humans. Immunocompromised BXN (bg/bg xid/xid nu/nu) mice were infected with either the sensitive NF54 strain or the multiresistant T24 strain and then treated with chloroquine, quinine, mefloquine, or dihydroartemisinin. A parallelism was observed between previously reported human responses and P. falciparum-parasitized human red blood cell (huRBC)--BXN mouse responses to classical antimalarial drugs, measured in terms of speed of decrease in parasitemia and of morphological alterations of the parasites. Mice infected with the sensitive strain were successfully cured after treatment with either chloroquine or mefloquine. In contrast, mice infected with the multiresistant strain failed to be cured by chloroquine or quinine but thereafter responded to dihydroartemisinin treatment. The speed of parasite clearance and the morphological alterations induced differed for each drug and matched previously reported observations, hence stressing the relevance of the model. These data thus suggest that P. falciparum-huRBC-BXN mice can provide a valuable in vivo system and should be included in the short list of animals that can be used for the evaluation of P. falciparum responses to drugs.

Artemether-lumefantrine for the treatment of multidrug-resistant falciparum malaria

The efficacy and safety of the 6-dose regimen of artemether-lumefantrine were assessed in an open randomized trial in children and adults presenting with acute, uncomplicated Plasmodium falciparum malaria in Thailand between November 1997 and March 1998. 200 patients were enrolled in 2 centres: 150 received artemether-lumefantrine (i.e., a median total dose of 9.6 mg/kg [interquartile range 8.7-10.7] and 57.9 mg/kg of lumefantrine [52.4-64.0]) and 50 the standard combination of artesunate (12 mg/kg over 3 d) and mefloquine (25 mg/kg). All patients had rapid initial clinical and parasitological responses. The 28 d cure rates were high: 97.7% (95% confidence interval [95% CI] 93.5-99.5%) for artemether-lumefantrine and 100% (95% CI 92.5-100%) for artesunate-mefloquine. The 6-dose regimen of artemether-lumefantrine was better tolerated than, and as effective as, artesunate-mefloquine, the current standard treatment in this area of multidrug-resistant P. falciparum malaria.

Extracts from "Clinical Evidence". Malaria: prevention in travellers

DEFINITION

Malaria is caused by a protozoan infection of red blood cells with one of four species of the genus plasmodium: P falciparum, P vivax, P ovale, or P malariae. Clinically, malaria may present in different ways, but it is usually characterised by fever (which may be swinging), tachycardia, rigors, and sweating. Anaemia, hepatosplenomegaly, cerebral involvement, renal failure, and shock may occur. INCIDENCE/PREVALENCE: Each year there are 300-500 million clinical cases of malaria. About 40% of the world's population is at risk of acquiring the disease. Each year 25-30 million people from non-tropical countries visit areas in which malaria is endemic, of whom between 10,000 and 30,000 contract malaria. AETIOLOGY/RISK FACTORS: Malaria is mainly a rural disease, requiring standing water nearby. It is transmitted by bites from infected female anopheline mosquitoes, mainly at dusk and during the night. In cities, mosquito bites are usually from female culicene mosquitoes, which are not vectors of malaria. Malaria is resurgent in most tropical countries and the risk to travellers is increasing.

PROGNOSIS

Ninety per cent of travellers who contract malaria do not become ill until after they return home. "Imported malaria" is easily treated if diagnosed promptly, and it follows a serious course in only about 12% of people. The most severe form of the disease is cerebral malaria, with a case fatality rate in adult travellers of 2-6%, mainly because of delays in diagnosis.

AIMS

To reduce the risk of infection; to prevent illness and death.

OUTCOMES

Rates of malarial illness and death, and adverse effects of treatment. Proxy measures include number of mosquito bites and number of mosquitoes in indoor areas. We found limited evidence linking number of mosquito bites and risk of malaria.

METHODS

Clinical Evidence search and appraisal in November 1999. We reviewed all identified systematic reviews and randomised controlled trials (RCTs).

Comparative clinical trial of four regimens of dihydroartemisinin-mefloquine in multidrug-resistant falciparum malaria

We conducted a randomized, comparative trial at the Bangkok Hospital for Tropical Diseases during 1996-98 to evaluate the clinical efficacy and tolerability of four combination regimens of dihydroartemisinin-mefloquine. 207 male patients aged 18-25 years, weighing 49.3-55.1 kg were randomized to receive a single oral dose of 300 mg dihydroartemisinin plus one or two doses of mefloquine as follows: regimen I (n = 26): 750 mg mefloquine concurrently, or regimen II (n = 22): 750 mg mefloquine 24 h later, or regimen III (n = 78): 750 and 500 mg mefloquine at 24 and 30 h, or regimen IV (n = 81): 750 and 500 mg mefloquine (at 0 and 24 h). All patients improved clinically within 24 h of initiation of treatment. The initial therapeutic response was rapid and identical in all treatment groups (median PCT vs. FCT: 36 vs. 24, 36 vs. 28, 36 vs. 26, and 34 vs. 26 h, for regimen I, II, III and IV, respectively). All combination regimens generally showed acceptable tolerability profiles. Compliance with follow-up (42 days) was achieved by 86.5% (179 cases). Recrudescent parasitaemia was significantly higher in patients treated with low-dose mefloquine combinations (regimens I, II:8/23, 9/16) than in those who received high-dose mefloquine (regimens III, IV: 2/70, 3/70). No RII or RIII type of response was observed. There were no significant differences in susceptibility to mefloquine between primary and recrudescent isolates. Dose-adjusted whole blood mefloquine concentrations were significantly higher in high-dose mefloquine regimens (III and IV). Patients who vomited within the first hour of mefloquine administration had markedly lower whole blood mefloquine concentrations than those who did not vomit.

Preventing antimalarial drug resistance through combinations

Throughout the tropical world antimalarial drug resistance is increasing, particularly in the potentially lethal malaria parasite Plasmodium falciparum. In some parts of Southeast Asia, parasites which are resistant to chloroquine, pyrimethamine-sulfadoxine, and mefloquine are prevalent. The characteristics of a drug that make it vulnerable to the development of resistance are a long terminal elimination half-life, a shallow concentration-effect relationship, and that one or two base-pair mutations confer a marked reduction in susceptibility. The development of resistance can be delayed or prevented by drug combinations. The artemisinin derivatives are the most potent of all antimalarial drugs. They reduce the infecting parasite biomass by approximately 10 000-fold per asexual life cycle. There are good arguments for combining, de novo, an artemisinin derivative with all newly introduced antimalarial drugs.

Predictors of mefloquine treatment failure: a prospective study of 1590 patients with uncomplicated falciparum malaria

The factors which identify patients at risk of treatment failure were characterized in 1590 children and adults with uncomplicated falciparum malaria treated with 15 or 25 mg/kg of mefloquine on the borders of Thailand. Six independent predictors of failure were identified using multiple logistic regression. Age < or = 2 years (odds ratio [OR] 4.54), 3-15 years (OR 4.4), vomiting < 30 min after a single dose of 25 mg/kg (despite re-administration of the dose) (OR 2.5) and diarrhoea after treatment (OR 3.6) were the strongest predictors of failure by day 7. Parasitaemias > 10 000/mm3 (OR 1.4), and fever with a history of recent vomiting (OR 1.6) were risk factors for recrudescence of the infection between days 10 and 28. Patients treated with mefloquine in the previous 2 months were also at increased risk of failure (OR 2.38), particularly if they were anaemic (haematocrit < 30%) (OR 5.96), which suggested that they had recrudescent infections at presentation. Combined, these 6 factors identified half of all treatment failures. Vomiting and diarrhoea accounted for 24% of the early failures in children. Patients at increased risk of treatment failure should be monitored closely and given early alternative treatment if fever and parasites persist for > or = 3 d.

Artesunate. A review of its pharmacology and therapeutic efficacy in the treatment of malaria

Artesunate is an antimalarial agent, available in oral, rectal and parenteral formulations, that provides a rapid clinical effect in patients with Plasmodium falciparum malaria. The rapidity of effect, availability of an intravenous and intramuscular formulation and convenient dosage regimen make artesunate an ideal candidate for the treatment of severe malaria, including cerebral disease. While some results have been promising, there is no clear evidence to date that artesunate reduces mortality in patients with cerebral malaria to any greater extent than standard quinine therapy. When given as monotherapy, treatment should be continued for at least 5 to 7 days to prevent recrudescence. Combination therapy with mefloquine allows artesunate to be administered over 3 days or less, with a satisfactory clinical outcome maintained. Although optimal dosages remain to be determined, this combination continues to provide the rapid onset of clinical effect observed with artesunate monotherapy, but decreases the rate of recrudescence to 2% (i.e. radical cure rate of 98%) when used as treatment in patients with uncomplicated malaria from areas with a high risk of multidrug-resistance falciparum malaria. Although assessment of tolerability is complicated by the difficulty of distinguishing between disease- and treatment-related events, artesunate and artesunate-mefloquine combinations appear to be well tolerated in adults and children. Indeed, it is possible that prior administration of artesunate may reduce the incidence of mefloquine-induced vomiting. Clinical findings to date have not revealed any pattern of resistance to artesunate after use of the drug. However, given the history of the development of resistance to other antimalarial drugs, the use of artesunate should be restricted to areas of multidrug resistance, the drug should be used in combination with a longer acting agent such as mefloquine, and it should be used in regimens that provide radical cure rates of 90 to 100%. If used according to these treatment principles, artesunate will provide a well tolerated and valuable addition to the current extremely limited treatment options for multidrug-resistant falciparum malaria, a widespread parasitic disease associated with considerable mortality.

Mefloquine treatment of acute falciparum malaria: a prospective study of non-serious adverse effects in 3673 patients

Between 1990 and 1994, a series of prospective studies were conducted to optimize the treatment of multidrug-resistant falciparum malaria on the borders of Thailand. The tolerance of various treatment regimens containing either mefloquine 15 mg/kg (M15) or 25 mg/kg (M25) was evaluated in 3673 patients aged between 6 months and 88 years. Early vomiting (within 1 hour) is an important determinant of treatment outcome in these areas, despite re-administration of the dose. Overall, 7 % of the patients vomited within an hour. Significant risk factors were age < or = 6 years (relative risk (RR), 3.9) or > or 50 years (RR, 2.7), the higher mefloquine dose (M25) (RRm 2.7), vomiting < 24 hours before enrolment (RR, 2.5), axillary temperature > 38.0 degrees C (RR, 1.6), and parasitaemia > 10,000/microliter (RR, 1.3). In children < or = 2 years, 30% vomited with M25, and 13% did not tolerate a repeat dose. Vomiting was reduced 40% by splitting the higher dose (RR, 0.6; 95% CI, 0.4-0.8), and 50% by giving mefloquine on the second day in combination with artesunate (RR, 0.5; CI, 0.3-0.9). Anorexia, nausea, vomiting, dizziness, and sleeping disorders were 1.1-1.4 times more frequent with M25 than M15 in the three days following treatment, but were similar in the single or split-dose M25 groups, despite twofold higher mefloquine concentrations obtained with the latter. There was no evidence that diarrhoea, headache, and abdominal pain were associated with mefloquine use. High-dose mefloquine is well tolerated but should be given as a split dose.