Comparison of artemether and quinine in the treatment of severe falciparum malaria in south-east Thailand

Comparative efficacy and safety of the artemisinin derivatives compared to quinine for treating severe malaria in children and adults: A systematic update of literature and network meta-analysis

BACKGROUND

The artemisinin derivatives are the preferred antimalaria drugs for treating severe Plasmodium falciparum malaria. However, their clinical effectiveness compared to each other is unknown. Our objective, therefore, was to evaluate the efficacy and safety of the artemisinin derivatives and quinine for treating severe P. falciparum malaria in children and adults using a network meta-analysis.

METHODS AND FINDINGS

Review protocol was registered with PROSPERO, CRD42020218190. We updated the search strategies of three Cochrane systematic reviews which included published and unpublished randomised control trials (RCTs) that have compared specific artemisinin derivatives to quinine in treating severe malaria. Search included CENTRAL, MEDLINE, Embase, LILACS, ISI Web of Science and trial registries up to February 2021. We screened studies, extracted data, assessed risk of bias, and quality of evidence in duplicate. Separate network meta-analyses in the frequentist framework, using a random effects model, with quinine as reference, were conducted for adults and children, and rankings were produced using p-scores to assess mortality, parasite clearance, coma recovery, fever clearance, neurological sequela and adverse events. Searches identified 818 citations, 33 RCTs were eligible. We pooled 7795 children and 3182 adults. The networks involved artesunate, artemether, rectal artemisinin, arteether and quinine. Compared to quinine, artesunate reduced mortality in children (risk ratio (RR), 0.76; 95%CI [0.65 to 0.89], moderate quality), adults (RR, 0.55; 95%CI [0.40 to 0.75], moderate quality) and in cerebral malaria (RR, 0.72; 95%CI [0.55 to 0.94], moderate quality). Compared to rectal artemisinin and intramuscular arteether, the efficacy and safety of parenteral artesunate, and intramuscular artemether in treating severe malaria are not clear. Rankings showed that none of the artemisinin drugs were consistently superior in all the outcomes assessed. Indirect evidence produced were of very low ratings due to suspected publication bias and imprecision.

CONCLUSIONS

Artesunate reduces mortality compared to quinine for both adults and children in Asia and Africa including cerebral malaria. The artemisinin derivatives remain the best treatment for severe malaria but their comparative clinical effectiveness is yet to be fully explored.

Artemether for severe malaria

BACKGROUND

In 2011 the World Health Organization (WHO) recommended parenteral artesunate in preference to quinine as first-line treatment for people with severe malaria. Prior to this recommendation many countries, particularly in Africa, had begun to use artemether, an alternative artemisinin derivative. This Cochrane Review evaluates intramuscular artemether compared with both quinine and artesunate.

OBJECTIVES

To assess the efficacy and safety of intramuscular artemether versus any other parenteral medication in the treatment of severe malaria in adults and children.

SEARCH METHODS

We searched the Cochrane Infectious Diseases Group Specialized Register, CENTRAL (the Cochrane Library), MEDLINE, Embase, and LILACS, ISI Web of Science, conference proceedings, and reference lists of articles. We also searched the WHO International Clinical Trial Registry Platform, ClinicalTrials.gov, and the metaRegister of Controlled Trials (mRCT) for ongoing trials up to 7 September 2018. We checked the reference lists of all studies identified by the search. We examined references listed in review articles and previously compiled bibliographies to look for eligible studies.

SELECTION CRITERIA

Randomized controlled trials (RCTs) comparing intramuscular artemether with intravenous/intramuscular quinine or artesunate for treating severe malaria.

DATA COLLECTION AND ANALYSIS

The primary outcome was all-cause death. Two review authors independently screened each article by title and abstract, and examined potentially relevant studies for inclusion using an eligibility form. Two review authors independently extracted data and assessed risk of bias of included studies. We summarized dichotomous outcomes using risk ratios (RRs) and continuous outcomes using mean differences (MDs), and have presented both measures with 95% confidence intervals (CIs). Where appropriate, we combined data in meta-analyses and used the GRADE approach to summarize the certainty of the evidence.

MAIN RESULTS

We included 19 RCTs, enrolling 2874 adults and children with severe malaria, carried out in Africa (12 trials) and in Asia (7 trials).Artemether versus quinineFor children, there is probably little or no difference in the risk of death between intramuscular artemether and quinine (RR 0.97, 95% CI 0.77 to 1.21; 13 trials, 1659 participants, moderate-certainty evidence). Coma resolution time may be about five hours shorter with artemether (MD -5.45, 95% CI -7.90 to -3.00; six trials, 358 participants, low-certainty evidence). Artemether may make little difference to neurological sequelae (RR 0.84, 95% CI 0.66 to 1.07; seven trials, 968 participants, low-certainty evidence). Compared to quinine, artemether probably shortens the parasite clearance time by about nine hours (MD -9.03, 95% CI -11.43 to -6.63; seven trials, 420 participants, moderate-certainty evidence), and may shorten the fever clearance time by about three hours (MD -3.73, 95% CI -6.55 to -0.92; eight trials, 457 participants, low-certainty evidence).For adults, treatment with intramuscular artemether probably results in fewer deaths than treatment with quinine (RR 0.59, 95% CI 0.42 to 0.83; four trials, 716 participants, moderate-certainty evidence).Artemether versus artesunateArtemether and artesunate have not been directly compared in randomized trials in children.For adults, mortality is probably higher with intramuscular artemether (RR 1.80, 95% CI 1.09 to 2.97; two trials, 494 participants, moderate-certainty evidence).

AUTHORS' CONCLUSIONS

Artemether appears to be more effective than quinine in children and adults. Artemether compared to artesunate has not been extensively studied, but in adults it appears inferior. These findings are consistent with the WHO recommendations that artesunate is the drug of choice, but artemether is acceptable when artesunate is not available.

Treating severe malaria in pregnancy: a review of the evidence

Severe malaria in pregnancy is a large contributor to maternal morbidity and mortality. Intravenous quinine has traditionally been the treatment drug of choice for severe malaria in pregnancy. However, recent randomized clinical trials (RCTs) indicate that intravenous artesunate is more efficacious for treating severe malaria, resulting in changes to the World Health Organization (WHO) treatment guidelines. Artemisinins, including artesunate, are embryo-lethal in animal studies and there is limited experience with their use in the first trimester. This review summarizes the current literature supporting 2010 WHO treatment guidelines for severe malaria in pregnancy and the efficacy, pharmacokinetics, and adverse event data for currently used antimalarials available for severe malaria in pregnancy. We identified ten studies on the treatment of severe malaria in pregnancy that reported clinical outcomes. In two studies comparing intravenous quinine with intravenous artesunate, intravenous artesunate was more efficacious and safe for use in pregnant women. No studies detected an increased risk of miscarriage, stillbirth, or congenital anomalies associated with first trimester exposure to artesunate. Although the WHO recommends using either quinine or artesunate for the treatment of severe malaria in first trimester pregnancies, our findings suggest that artesunate should be the preferred treatment option for severe malaria in all trimesters.

Artemether for severe malaria

BACKGROUND

In 2011 the World Health Organization (WHO) recommended parenteral artesunate in preference to quinine as first-line treatment for people with severe malaria. Prior to this recommendation, many countries, particularly in Africa, had begun to use artemether, an alternative artemisinin derivative. This review evaluates intramuscular artemether compared with both quinine and artesunate.

OBJECTIVES

To assess the efficacy and safety of intramuscular artemether versus any other parenteral medication in treating severe malaria in adults and children.

SEARCH METHODS

We searched the Cochrane Infectious Diseases Group Specialized Register, CENTRAL (The Cochrane Library), MEDLINE, EMBASE and LILACS, ISI Web of Science, conference proceedings and reference lists of articles. We also searched the WHO clinical trial registry platform, ClinicalTrials.gov and the metaRegister of Controlled Trials (mRCT) for ongoing trials up to 9 April 2014.

SELECTION CRITERIA

Randomized controlled trials (RCTs) comparing intramuscular artemether with intravenous or intramuscular antimalarial for treating severe malaria.

DATA COLLECTION AND ANALYSIS

The primary outcome was all-cause death.Two authors independently assessed trial eligibility, risk of bias and extracted data. We summarized dichotomous outcomes using risk ratios (RR) and continuous outcomes using mean differences (MD), and presented both measures with 95% confidence intervals (CI). Where appropriate, we combined data in meta-analyses and assessed the quality of the evidence using the GRADE approach.

MAIN RESULTS

We included 18 RCTs, enrolling 2662 adults and children with severe malaria, carried out in Africa (11) and in Asia (7). Artemether versus quinine For children in Africa, there is probably little or no difference in the risk of death between intramuscular artemether and quinine (RR 0.96, 95% CI 0.76 to 1.20; 12 trials, 1447 participants, moderate quality evidence). Coma recovery may be about five hours shorter with artemether (MD -5.45, 95% CI -7.90 to -3.00; six trials, 358 participants, low quality evidence), and artemether may result in fewer neurological sequelae, but larger trials would be needed to confirm this (RR 0.84, 95% CI 0.66 to 1.07; seven trials, 968 participants, low quality evidence). Artemether probably shortens the parasite clearance time by about nine hours (MD -9.03, 95% CI -11.43 to -6.63; seven trials, 420 participants, moderate quality evidence), and may shorten the fever clearance time by about three hours (MD -3.73, 95% CI -6.55 to -0.92; eight trials, 457 participants, low quality evidence).For adults in Asia, treatment with intramuscular artemether probably results in fewer deaths than treatment with quinine (RR 0.59, 95% CI 0.42 to 0.83; four trials, 716 participants, moderate quality evidence). Artemether versus artesunate Artemether and artesunate have not been directly compared in randomized trials in African children.For adults in Asia, mortality is probably higher with intramuscular artemether (RR 1.80, 95% CI 1.09 to 2.97, two trials,494 participants, moderate quality evidence).

AUTHORS' CONCLUSIONS

Although there is a lack of direct evidence comparing artemether with artesunate, artemether is probably less effective than artesunate at preventing deaths from severe malaria. In circumstances where artesunate is not available, artemether is an alternative to quinine.

Artesunate for severe acute Plasmodium falciparum infection in a patient with myasthenia gravis

We report a case of severe malaria in a patient with underlying myasthenia gravis who was successfully treated with artesunate. The outcome was favorable. Artesunate seems to be a good option for patients with underlying myasthenia gravis disease because they benefit from a better toxicity profile than quinine.

Possible role of heme oxygenase-1 and prostaglandins in the pathogenesis of cerebral malaria: heme oxygenase-1 induction by prostaglandin D(2) and metabolite by a human astrocyte cell line

Astrocytes are the most abundant cells in the central nervous system that play roles in maintaining the blood-brain-barrier and in neural injury, including cerebral malaria, a severe complication of Plasmodium falciparum infection. Prostaglandin (PG) D(2) is abundantly produced in the brain and regulates the sleep response. Moreover, PGD(2) is a potential factor derived from P. falciparum within erythrocytes. Heme oxygenase-1 (HO-1) is catalyzing enzyme in heme breakdown process to release iron, carbon monoxide, and biliverdin/bilirubin, and may influence iron supply to the P. falciparum parasites. Here, we showed that treatment of a human astrocyte cell line, CCF-STTG1, with PGD(2) significantly increased the expression levels of HO-1 mRNA by RT-PCR. Western blot analysis showed that PGD(2) treatment increased the level of HO-1 protein, in a dose- and time-dependent manner. Thus, PGD(2) may be involved in the pathogenesis of cerebral malaria by inducing HO-1 expression in malaria patients.

Randomised trial of artemether versus artemether and mefloquine for the treatment of chloroquine/sufadoxine-pyrimethamine-resistant falciparum malaria during pregnancy

The efficacy of artemether and artemether followed by mefloquine was evaluated in 45 pregnant women with drug resistant Plasmodium falciparum malaria during the second and third trimesters. There was prompt clinical response to both treatment regimens. The parasite and fever clearance times and the cure rate were similar in both groups. Except for the correlation between initial parasite density and fever clearance time in the artemether-mefloquine group, there was no correlation between initial parasite density and parasite or fever clearance times in the two groups. Similarly, there was no correlation between parasite and fever clearance. Both treatment regimens were well tolerated. All newborn babies of the participating women were normal at birth. Physical and neurodevelopmental assessment of the newborn babies followed up for a period varying between 6 and 36 months were within normal limits. Artemether alone or with mefloquine are effective and do not produce undue deleterious effects in pregnant patients with drug-resistant falciparum malaria during the second and third trimesters.

Effects of weight, age, and time on artemether–lumefantrine associated ototoxicity and evidence of irreversibility

An association between artemether-lumefantrine treatment of uncomplicated falciparum malaria and decreases in audiometrically determined hearing thresholds has been reported. Questions arising from this report were whether the effect described is attributable to drug or disease, the effects of subject weight and age on audiometric changes, and whether the changes are reversible. Spearman's correlation coefficients were calculated to look for relationships between audiometric changes and: (1) the interval spanning artemether-lumefantrine exposure and study exit audiogram; (2) subject age; (3) subject weight. The study utilised prospectively collected data from an occupational health clinic in Mozambique (N = 150). The exposure-exit audiogram interval ranged from 3 to 392 days (mean 163.8 days, SD 91.91 days). Spearman's correlation coefficients were effectively zero for analyses (1) and (2), and too weak to contribute significantly to variances for analysis (3). Previous audiometric studies in malaria patients and healthy volunteers point away from malaria as causing irreversible audiometric changes. The audiometric changes associated with the artemether-lumefantrine treatment of malaria appear irreversible. Ototoxicity is common to many antimalarials and the elucidation of a common antiparasitic and ototoxic pathway will assist in the design of safer new antimalarials.

Artemisinins

Artemisinins were discovered to be highly effective antimalarial drugs shortly after the isolation of the parent artemisinin in 1971 in China. These compounds combine potent, rapid antimalarial activity with a wide therapeutic index and an absence of clinically important resistance. Artemisinin containing regimens meet the urgent need to find effective treatments for multidrug resistant malaria and have recently been advocated for widespread deployment. Comparative trials of artesunate and quinine for severe malaria are in progress to see if the persistently high mortality of this condition can be reduced.

Antimalarial Drug Toxicity

Malaria, caused mostly by Plasmodium falciparum and P. vivax, remains one of the most important infectious diseases in the world. Antimalarial drug toxicity is one side of the risk-benefit equation and is viewed differently depending upon whether the clinical indication for drug administration is malaria treatment or prophylaxis. Drug toxicity must be acceptable to patients and cause less harm than the disease itself. Research that leads to drug registration tends to omit two important groups who are particularly vulnerable to malaria--very young children and pregnant women. Prescribing in pregnancy is a particular problem for clinicians because the risk-benefit ratio is often very unclear. The number of antimalarial drugs in use is very small. Despite its decreasing efficacy against P. falciparum, chloroquine continues to be used widely because of its low cost and good tolerability. It remains the drug of first choice for treating P. vivax malaria. Pruritus is a common adverse effect in African patients. As prophylaxis, chloroquine is usually combined with proguanil. This combination has good overall tolerability but mouth ulcers and gastrointestinal upset are more common than with other prophylactic regimens. Sulfadoxine/pyrimethamine is well tolerated as treatment and when used as intermittent preventive treatment in pregnant African women. Sulfadoxine/pyrimethamine is no longer used as prophylaxis because it may cause toxic epidermal necrolysis and Stevens Johnson syndrome. Mefloquine remains a valuable drug for prophylaxis and treatment. Tolerability is acceptable to most patients and travellers despite the impression given by the lay press. Dose-related serious neuropsychiatric toxicity can occur; mefloquine is contraindicated in individuals with a history of epilepsy or psychiatric disease. Quinine is the mainstay for treating severe malaria in many countries. Cardiovascular or CNS toxicity is rare, but hypoglycaemia may be problematic and blood glucose levels should be monitored. Halofantrine is unsuitable for widespread use because of its potential for cardiotoxicity. There is renewed interest in two old drugs, primaquine and amodiaquine. Primaquine is being developed as prophylaxis, and amodiaquine, which was withdrawn from prophylactic use because of neutropenia and hepatitis, is a potentially good partner drug for artesunate against falciparum malaria. Atovaquone/proguanil is a new antimalarial combination with good efficacy and tolerability as prophylaxis and treatment. The most important class of drugs that could have a major impact on malaria control is the artemisinin derivatives. They have remarkable efficacy and an excellent safety record. They have no identifiable dose-related adverse effects in humans and only very rarely produce allergic reactions. Combining an artemisinin derivative with another efficacious antimalarial drug is increasingly being viewed as the optimal therapeutic strategy for malaria.

A meta-analysis using individual patient data of trials comparing artemether with quinine in the treatment of severe falciparum malaria

We conducted a meta-analysis using individual patient data from randomized controlled trials comparing artemether and quinine in severe falciparum malaria. Eleven trials were identified, of which 8 were clearly randomized. Original individual patient data on 1919 patients were obtained from 7 trials, representing 85% of the patients in the original 11 studies. Overall there were 136 deaths among the 961 patients treated with artemether, compared with 164 in the 958 treated with quinine [14% vs 17%, odds ratio (95% confidence interval) 0.8 (0.62 to 1.02), P = 0.08]. There were no differences between the 2 treatment groups in coma recovery or fever clearance times, or the development of neurological sequelae. However, the combined 'adverse outcome' of either death or neurological sequelae was significantly less common in the artemether group [odds ratio (95% CI) 0.77 (0.62 to 0.96), P = 0.02], and treatment with artemether was associated with significantly faster parasite clearance [hazard ratio (95% CI) 0.62 (0.56 to 0.69), P < 0.001]. In subgroup analyses artemether was associated with a significantly lower mortality than quinine in adults with multisystem failure. In the treatment of severe falciparum malaria artemether is at least as effective as quinine in terms of mortality and superior to quinine in terms of overall serious adverse events. There was no evidence of clinical neurotoxicity or any other major side-effects associated with its use.

Artemisinin and its derivatives: an important new class of antimalarial agents

Artemisinin and its derivatives are a potent new class of antimalarials, originated from Artemisia annua, L. The clinical efficacy of these drugs is characterized by an almost immediate onset and rapid reduction of parasitaemia. Their efficacy is high in such areas as well where multidrug-resistance is rampant, but in these areas, their combination with other (effective) antimalarials (e.g., mefloquine) is highly recommended. In this short review, the chemical structures, pharmacological properties, and clinical uses of artemisinin drugs are discussed.

Artemisinin derivatives for treating severe malaria

BACKGROUND

Artemisinin derivatives may have advantages over quinoline drugs for treating severe malaria since they are fast acting and effective against quinine resistant malaria parasites.

OBJECTIVES

The objective of this review was to assess the effects of artemisinin drugs for severe and complicated falciparum malaria in adults and children.

SEARCH STRATEGY

We searched the Cochrane Infectious Diseases Group trials register, Cochrane Controlled Trials Register, Medline, Embase, Science Citation Index, Lilacs, African Index Medicus, conference abstracts and reference lists of articles. We contacted organisations, researchers in the field and drug companies.

SELECTION CRITERIA

Randomised and pseudo-randomised trials comparing artemisinin drugs (rectal, intramuscular or intravenous) with standard treatment, or comparisons between artemisinin derivatives in adults or children with severe or complicated falciparum malaria.

DATA COLLECTION AND ANALYSIS

Eligibility, trial quality assessment and data extraction were done independently by two reviewers. Study authors were contacted for additional information.

MAIN RESULTS

Twenty three trials are included, allocation concealment was adequate in nine. Sixteen trials compared artemisinin drugs with quinine in 2653 patients. Artemisinin drugs were associated with better survival (mortality odds ratio 0.61, 95% confidence interval 0.46 to 0.82, random effects model). In trials where concealment of allocation was adequate (2261 patients), this was barely statistically significant (odds ratio 0.72, 95% CI 0.54 to 0.96, random effects model). In 1939 patients with cerebral malaria, mortality was also lower with artemisinin drugs overall (odds ratio 0.63, 95% CI 0.44 to 0.88, random effects model). The difference was not significant however when only trials reporting adequate concealment of allocation were analysed (odds ratio 0.78, 95% CI 0.55 to 1.10, random effects model) based on 1607 patients. No difference in neurological sequelae was shown. Compared with quinine, artemisinin drugs showed faster parasite clearance from the blood and similar adverse effects.

REVIEWER'S CONCLUSIONS

The evidence suggests that artemisinin drugs are no worse than quinine in preventing death in severe or complicated malaria. No artemisinin derivative appears to be better than the others.

Current perspectives on pain upon injection of drugs

A limitation in the administration of parenteral products is the pain caused upon injection. Injection site pain has been predominately associated with intravenous, intramuscular, and subcutaneous administration. It becomes important for the formulation scientist to have a basic understanding of the physiology underlying the pain process, as well as the pharmaceutical factors associated with injection site pain. Initially, this review will provide the reader with a primer on the mediation of pain in the periphery and a compilation of those drugs that have been associated with pain on injection. In addition, this review will present important considerations and general formulation approaches or methods that have been used to overcome pain on injection. Finally, a brief overview of the various experimental systems used to investigate injection site pain is discussed.

Pharmacokinetics of intramuscular artemether in patients with severe falciparum malaria with or without acute renal failure

AIMS

The pharmacokinetics of intramuscular artemether and its major plasma metabolite-dihydroartemisinin, were investigated in patients with severe manifestations of falciparum malaria.

METHODS

Six severe falciparum malaria patients with acute renal failure (ARF) and 11 without ARF were recruited into the study. They were treated with intramuscular artemether at a loading dose of 160 mg, followed by daily doses of 80 mg for another 6 days (total dose 640 mg).

RESULTS

Patients with and without ARF showed a good initial response to treatment; the parasite and fever clearance times were 66(30-164) and 76(36-140) h [median(range)], respectively. None had reappearance of parasitaemia in their peripheral blood smear within 7 days of initiation of treatment. In comatose patients, the time to recovery of consciousness was 51.6(22-144) h. Artemether was detected in plasma as early as 1 h after a 160 mg dose, and declined to undetectable levels within 24 h in most cases. Patients with ARF had significantly higher Cmax [2.38(1.89-3.95) vs 1.56(1.05-3.38) ng ml(-1) mg(-1) dose], AUC [35.4(22-52.9) vs 25.2(13.4-52.9) ng ml(-1) h mg(-1) dose], and lower Vz/F [5.45(3.2-6.9) vs 8.6(4.2-12.3) l kg(-1)] and CL/F [7.4(5.4-13.8) vs 19.1(8.5-25.1) ml min(-1) kg(-1)] when compared with those without ARF. In addition, t1/2,z was significantly longer in ARF patients [7.0(5.5-10.0) vs 5.7(4.2-6.6) h]. The pharmacokinetics of dihydroartemisinin in the two groups of patients were comparable.

CONCLUSIONS

ARF significantly modified the pharmacokinetics of intramuscular artemether. The changes could be attributed to either improved absorption/bioavailability, a reduction of systemic clearance, or a change in plasma protein binding of the drug.

Simple high-performance liquid chromatographic method with electrochemical detection for the simultaneous determination of artesunate and dihydroartemisinin in biological fluids

A simple, rapid, sensitive, selective and reproducible high-performance liquid chromatographic method with reductive electrochemical detection is described for the simultaneous quantification of artesunate (ARS) and dihydroartemisinin (DHA) in plasma. The procedure involved the extraction of ARS, DHA and the internal standard (artemisinin, ARN) with a mixture of dichloromethane and tert.-methyl butyl ether (8:2, v/v). Chromatographic separation consisted of the mobile phase (acetonitrile-water containing 0.1 M acetic acid, pH 4.8; 45:55, v/v) running through the column (Nova-Pak C18, 150 cm x 3.9 mm I.D., 5 microm particle size). The retention times of alpha-DHA, beta-DHA, ARS and ARN were 2.9, 4.2, 4.5 and 6.0 min, respectively. The average recoveries of ARS, alpha-DHA and ARN in the concentration range of 10-800 ng/ml were 81.9, 88.2, 101.1 and 84.3%, respectively. The coefficients of variation (precision and repeatability) were below 10% for all three compounds at concentrations of 50, 200, 400 and 800 ng/ml, and below 20% at a concentration of 10 ng/ml. The limits of quantification for both ARS and alpha-DHA in spiked plasma samples were 5 and 3 ng/ml, respectively. The method was found to be suitable for application to pharmacokinetic studies of both ARS and DHA.

Incidence of antimalarial pretreatment and drug sensitivity in vitro in multidrug-resistant Plasmodium falciparum infection in Thailand

Blood samples for determination of baseline antimalarial levels and sensitivity testing in vitro were collected from 411 patients with uncomplicated multidrug-resistant Plasmodium falciparum malaria (365 males, 46 females) before starting antimalarial treatment (62 in hospital and 349 as out-patients). Three hundred and eighty-two were successfully tested, and 110 (28.8%) and 20 (5.2%) patients, respectively, had detectable baseline blood mefloquine and quinine levels. Thirty-nine (10.2%), 44 (11.5%), 23 (6.0%) and 4 (1.1%) cases, respectively, had mefloquine concentrations in whole blood of < 100, 100-500, > 500-1000 and > 1000 ng/mL; the corresponding values for baseline plasma quinine levels were 0 (0%), 9 (2.4%), 3 (0.8%) and 9 (2.4%). None had detectable baseline artemether or artesunate. Sensitivity tests in vitro of pretreatment P. falciparum isolates showed the median IC50, IC90 and IC99 values (ranges in parentheses) for mefloquine, quinine and artemisinin to be 0.121 (0.046-0.715), 0.333 (0.085-3.0) and 0.64 (0.16-1.28) microM, 0.256 (0.064-1.315), 1.10 (0.154-20.49) and 2.56 (0.64-5.12) microM, and 0.02 (0.003-0.382), 0.112 (0.015-4.3) and 0.3 (0.03-3.0) microM, respectively. There was no difference in the sensitivity of P. falciparum isolates to these antimalarial compounds, regardless of the areas where patients had contracted the infection. Previous treatment with mefloquine or quinine was not statistically associated with a high incidence of resistance to these compounds.

Severe and complicated malaria treated with artemisinin, artesunate or artemether in Viet Nam

One hundred and seventy five Vietnamese adults with severe and complicated malaria admitted to a rural district hospital were entered into an open randomized comparative study to compare 4 treatment regimens based on artemisinin and its derivatives. The median time of defervescence was 48 h (95% confident interval [CI] 38-58 h) in those given intramuscular (i.m.) artemether, 42 h (95% CI 36-48 h) in those given artemisinin suppositories, 36 h (95% CI 30-42 h) in those receiving artesunate (i.m.) and 30 h (95% CI 18-42 h) in those receiving intravenous artesunate (P = 0.13). The respective median parasite clearance times were 30 h (95% CI 26-34 h), 30 h (95% CI 24-36 h), 24 h (95% CI 15-33 h), and 24 h (95% CI 15-33 h) (P = 0.30); the median times for recovery of consciousness were 47 h (95% CI 31-63 h), 24 h (95% CI 18-30 h), 30 h (95% CI 18-42 h), and 24 h (95% CI 4-44 h) (P = 0.18); and the mortality rates were 11.1%, 17.6%, 10.2% and 16.6%, respectively (P = 0.64). There was no significant difference in efficacy between the 4 treatments.

alpha, beta-Arteether for the treatment of complicated falciparum malaria

alpha, beta-Arteether is an ethyl ether derivative of artemisinin which is an efficient schizontocidal drug in mild falciparum malaria. The present study reports the efficacy of the drug in severe falciparum malaria. Fifty patients with severe falciparum malaria were given intramuscular arteether, 150 mg, once daily on 3 consecutive days. The median fever clearance time was 72 h (range 12-120 h) and the median parasite clearance time was 2 d (range 1-4 d). Rapid recovery from coma was observed in cerebral malaria patients (after a median of 18 h, range 6-72 h). The recovery from other complications was also faster and complete. Two patients died; both had cerebral malaria and haemolytic jaundice, one had respiratory distress needing ventilatory support and the other had severe anaemia. Recrudescence within 28 d was observed in 7 patients. Drug toxicity or significant side effects were not noticed in any patient.

Clinical pharmacology and therapeutic potential of artemisinin and its derivatives in the treatment of malaria

Artemisinin and its derivatives are renowned for their potent antimalarial activity. They have found their way into clinical use in many areas where malaria is endemic. The in vitro concentration at which artemisinin can inhibit 50% of the growth of Plasmodium falciparum ranges from 3 to 30 micrograms/L. The fat-soluble derivatives artemether and arteether are approximately twice as active. The water-soluble dihydro-artemisinin and artesunate are 4 to 5 times more active in vitro. Artemisinin is available only for oral and rectal administration. Absorption is incomplete and elimination is fast, with and elimination half-life of 2 to 5 hours. Plasma concentrations after a single 500 mg oral dose most often exceed 200 micrograms/L. Artesunate and artemether can be considered as prodrugs. Biotransformation into the active metabolite dihydro-artemisinin occurs rapidly--almost immediately for artesunate. The reported elimination half-life of artesunate is less than 1 hour, and for artemether the figure is 3 to 11 hours. The pharmacokinetics of dihydro-artemisinin are not yet completely clear. Elimination is probably also rapid, with an elimination half-life of a few hours. Arteether, dissolved in oil for intramuscular administration, has a much longer elimination half-life of over 20 hours. The clinical efficacy of this group of drugs is characterised by an almost immediate onset and rapid reduction of parasitaemia, with complete clearance in most cases within 48 hours. Efficacy is high even in areas with multidrug-resistant parasite strains. To prevent recrudescence with monotherapy of these compounds, treatment needs to be extended beyond the disappearance of parasites. After 5 days of therapy the rate of recrudescence is approximately 10%. Alternatively, combination with other drugs can be used. Combination with mefloquine is recommended for areas with multidrug-resistant P. falciparum.

A controlled trial of artemether or quinine in Vietnamese adults with severe falciparum malaria

BACKGROUND

Artemisinin (qinghaosu) and its derivatives are rapidly effective antimalarial drugs derived from a Chinese plant. Preliminary studies suggest that these drugs may be more effective than quinine in the treatment of severe malaria. We studied artemether in Vietnam, where Plasmodium falciparum has reduced sensitivity to quinine.

METHODS

We conducted a randomized, double-blind trial in 560 adults with severe falciparum malaria. Two hundred seventy-six received intramuscular quinine dihydrochloride (20 mg per kilogram of body weight followed by 10 mg per kilogram every eight hours), and 284 received intramuscular artemether (4 mg per kilogram followed by 2 mg per kilogram every eight hours). Both drugs were given for a minimum of 72 hours.

RESULTS

There were 36 deaths in the artemether group (13 percent) and 47 in the quinine group (17 percent; P = 0.16; relative risk of death in the patients given artemether, 0.74; 95 percent confidence interval, 0.5 to 1.11). The parasites were cleared more quickly from the blood in the artemether group (mean, 72 vs. 90 hours; P < 0.001); however, in this group fever resolved more slowly (127 vs. 90 hours, P < 0.001), the time to recovery from coma was longer (66 vs. 48 hours, P = 0.003), and the hospitalization was longer (288 vs. 240 hours, P = 0.005). Quinine treatment was associated with a higher risk of hypoglycemia (relative risk, 2.7; 95 percent confidence interval, 1.7 to 4.4; P < 0.001), but there were no other serious side effects in either group.

CONCLUSIONS

Artemether is a satisfactory alternative to quinine for the treatment of severe malaria in adults.