Neurological, cardiovascular and metabolic effects of mefloquine in healthy volunteers: a double-blind, placebo-controlled trial

Drug-induced hyperinsulinemic hypoglycemia: An update on pathophysiology and treatment

The initial step for the differential diagnosis of hypoglycemia is to determine whether it is hyperinsulinemic or non hyperinsulinemic. Existing literature discusses drug-related hypoglycemia, but it misses a focus on drug-induced hyperinsulinemic hypoglycemia (DHH). Here we reviewed the association existing between drugs and hyperinsulinemic hypoglycemia. We primarily selected on the main electronic databases (MEDLINE, EMBASE, Web of Science, and SCOPUS) the reviews on drug-induced hypoglycemia. Among the drugs listed in the reviews, we selected the ones linked to an increase in insulin secretion. For the drugs missing a clear association with insulin secretion, we investigated the putative mechanism underlying hypoglycemia referring to the original papers. Our review provides a list of the most common agents associated with hyperinsulinemic hypoglycemia (HH), in order to facilitate both the recognition and the prevention of DHH. We also collected data about the responsiveness of DHH to diazoxide or octreotide.

The inhibitor of connexin Cx36 channels, mefloquine, inhibits voltage-dependent Ca2+ channels and insulin secretion

The antimalarial agent, mefloquine, inhibits the function of connexin Cx36 gap junctions and hemichannels and has thus become a tool to investigate their physiological relevance in pancreatic islets. In view of earlier reports on a KATP channel-block by mefloquine, the specificity of mefloquine as a pharmacological tool was investigated. Mouse pancreatic islets and single beta cells were used to measure membrane potential, whole cell currents, Ca2+ channel activity, cytosolic Ca2+ concentration ([Ca2+]i) and insulin secretion. Mefloquine was tested in the concentration range of 5-50 μM 25 μM mefloquine was as effective as 500 μM tolbutamide to depolarize the plasma membrane of beta cells, but did not induce action potentials. Rather, it abolished tolbutamide-induced action potentials and the associated increase of [Ca2+]i. In the range of 5-50 μM mefloquine inhibited voltage-dependent Ca2+ currents in primary beta cells as effectively as 1 μM nisoldipine, a specific blocker of L-type Ca2+ channels. The Ca2+ channel opening effect of Bay K8644 was completely antagonized by mefloquine. Likewise, the increase of [Ca2+]i and of insulin secretion stimulated by 40 mM KCl, but not that by 30 mM glucose was antagonized by 50 μM mefloquine. Neither at 5 μM nor at 50 μM did mefloquin stimulate insulin secretion at basal glucose. In conclusion, mefloquine blocks KATP channels and L-type Ca2+ channels in pancreatic beta cells in the range from 5 to 50 μM. Thus it inhibits depolarization-induced insulin secretion, but in the presence of a stimulatory glucose concentration additional effects of mefloquine, possibly on intracellular Ca2+ mobilization, and the metabolic amplification by glucose permit a sustained rate of secretion.

Mefloquine for preventing malaria during travel to endemic areas

BACKGROUND

Mefloquine is one of four antimalarial agents commonly recommended for preventing malaria in travellers to malaria-endemic areas. Despite its high efficacy, there is controversy about its psychological side effects.

OBJECTIVES

To summarize the efficacy and safety of mefloquine used as prophylaxis for malaria in travellers.

SEARCH METHODS

We searched the Cochrane Infectious Diseases Group Specialized Register; the Cochrane Central Register of Controlled Trials (CENTRAL), published on the Cochrane Library; MEDLINE; Embase (OVID); TOXLINE (https://toxnet.nlm.nih.gov/newtoxnet/toxline.htm); and LILACS. We also searched the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP; http://www.who.int/ictrp/en/) and ClinicalTrials.gov (https://clinicaltrials.gov/ct2/home) for trials in progress, using 'mefloquine', 'Lariam', and 'malaria' as search terms. The search date was 22 June 2017.

SELECTION CRITERIA

We included randomized controlled trials (for efficacy and safety) and non-randomized cohort studies (for safety). We compared prophylactic mefloquine with placebo, no treatment, or an alternative recommended antimalarial agent. Our study populations included all adults and children, including pregnant women.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the eligibility and risk of bias of trials, extracted and analysed data. We compared dichotomous outcomes using risk ratios (RR) with 95% confidence intervals (CI). Prespecified adverse outcomes are included in 'Summary of findings' tables, with the best available estimate of the absolute frequency of each outcome in short-term international travellers. We assessed the certainty of the evidence using the GRADE approach.

MAIN RESULTS

We included 20 RCTs (11,470 participants); 35 cohort studies (198,493 participants); and four large retrospective analyses of health records (800,652 participants). Nine RCTs explicitly excluded participants with a psychiatric history, and 25 cohort studies stated that the choice of antimalarial agent was based on medical history and personal preference. Most RCTs and cohort studies collected data on self-reported or clinician-assessed symptoms, rather than formal medical diagnoses. Mefloquine efficacyOf 12 trials comparing mefloquine and placebo, none were performed in short-term international travellers, and most populations had a degree of immunity to malaria. The percentage of people developing a malaria episode in the control arm varied from 1% to 82% (median 22%) and 0% to 13% in the mefloquine group (median 1%).In four RCTs that directly compared mefloquine, atovaquone-proguanil and doxycycline in non-immune, short-term international travellers, only one clinical case of malaria occurred (4 trials, 1822 participants). Mefloquine safety versus atovaquone-proguanil Participants receiving mefloquine were more likely to discontinue their medication due to adverse effects than atovaquone-proguanil users (RR 2.86, 95% CI 1.53 to 5.31; 3 RCTs, 1438 participants; high-certainty evidence). There were few serious adverse effects reported with mefloquine (15/2651 travellers) and none with atovaquone-proguanil (940 travellers).One RCT and six cohort studies reported on our prespecified adverse effects. In the RCT with short-term travellers, mefloquine users were more likely to report abnormal dreams (RR 2.04, 95% CI 1.37 to 3.04, moderate-certainty evidence), insomnia (RR 4.42, 95% CI 2.56 to 7.64, moderate-certainty evidence), anxiety (RR 6.12, 95% CI 1.82 to 20.66, moderate-certainty evidence), and depressed mood during travel (RR 5.78, 95% CI 1.71 to 19.61, moderate-certainty evidence). The cohort studies in longer-term travellers were consistent with this finding but most had larger effect sizes. Mefloquine users were also more likely to report nausea (high-certainty evidence) and dizziness (high-certainty evidence).Based on the available evidence, our best estimates of absolute effect sizes for mefloquine versus atovaquone-proguanil are 6% versus 2% for discontinuation of the drug, 13% versus 3% for insomnia, 14% versus 7% for abnormal dreams, 6% versus 1% for anxiety, and 6% versus 1% for depressed mood. Mefloquine safety versus doxycyclineNo difference was found in numbers of serious adverse effects with mefloquine and doxycycline (low-certainty evidence) or numbers of discontinuations due to adverse effects (RR 1.08, 95% CI 0.41 to 2.87; 4 RCTs, 763 participants; low-certainty evidence).Six cohort studies in longer-term occupational travellers reported our prespecified adverse effects; one RCT in military personnel and one cohort study in short-term travellers reported adverse events. Mefloquine users were more likely to report abnormal dreams (RR 10.49, 95% CI 3.79 to 29.10; 4 cohort studies, 2588 participants, very low-certainty evidence), insomnia (RR 4.14, 95% CI 1.19 to 14.44; 4 cohort studies, 3212 participants, very low-certainty evidence), anxiety (RR 18.04, 95% CI 9.32 to 34.93; 3 cohort studies, 2559 participants, very low-certainty evidence), and depressed mood (RR 11.43, 95% CI 5.21 to 25.07; 2 cohort studies, 2445 participants, very low-certainty evidence). The findings of the single cohort study reporting adverse events in short-term international travellers were consistent with this finding but the single RCT in military personnel did not demonstrate a difference between groups in frequencies of abnormal dreams or insomnia.Mefloquine users were less likely to report dyspepsia (RR 0.26, 95% CI 0.09 to 0.74; 5 cohort studies, 5104 participants, low certainty-evidence), photosensitivity (RR 0.08, 95% CI 0.05 to 0.11; 2 cohort studies, 1875 participants, very low-certainty evidence), vomiting (RR 0.18, 95% CI 0.12 to 0.27; 4 cohort studies, 5071 participants, very low-certainty evidence), and vaginal thrush (RR 0.10, 95% CI 0.06 to 0.16; 1 cohort study, 1761 participants, very low-certainty evidence).Based on the available evidence, our best estimates of absolute effect for mefloquine versus doxycyline were: 2% versus 2% for discontinuation, 12% versus 3% for insomnia, 31% versus 3% for abnormal dreams, 18% versus 1% for anxiety, 11% versus 1% for depressed mood, 4% versus 14% for dyspepsia, 2% versus 19% for photosensitivity, 1% versus 5% for vomiting, and 2% versus 16% for vaginal thrush.Additional analyses, including comparisons of mefloquine with chloroquine, added no new information. Subgroup analysis by study design, duration of travel, and military versus non-military participants, provided no conclusive findings.

AUTHORS' CONCLUSIONS

The absolute risk of malaria during short-term travel appears low with all three established antimalarial agents (mefloquine, doxycycline, and atovaquone-proguanil).The choice of antimalarial agent depends on how individual travellers assess the importance of specific adverse effects, pill burden, and cost. Some travellers will prefer mefloquine for its once-weekly regimen, but this should be balanced against the increased frequency of abnormal dreams, anxiety, insomnia, and depressed mood.

The antimalarial drug mefloquine inhibits cardiac inward rectifier K+ channels: evidence for interference in PIP2-channel interaction

The antimalarial drug mefloquine was found to inhibit the KATP channel by an unknown mechanism. Because mefloquine is a Cationic amphiphilic drug and is known to insert into lipid bilayers, we postulate that mefloquine interferes with the interaction between PIP2 and Kir channels resulting in channel inhibition. We studied the inhibitory effects of mefloquine on Kir2.1, Kir2.3, Kir2.3(I213L), and Kir6.2/SUR2A channels expressed in HEK-293 cells, and on IK1 and IKATP from feline cardiac myocytes. The order of mefloquine inhibition was Kir6.2/SUR2A ≈ Kir2.3 (IC50 ≈ 2 μM) > Kir2.1 (IC50 > 30 μM). Similar results were obtained in cardiac myocytes. The Kir2.3(I213L) mutant, which enhances the strength of interaction with PIP2 (compared to WT), was significantly less sensitive (IC50 = 9 μM). In inside-out patches, continuous application of PIP2 strikingly prevented the mefloquine inhibition. Our results support the idea that mefloquine interferes with PIP2-Kir channels interactions.

Drug-induced hypoglycaemia: an update

Drugs are the most frequent cause of hypoglycaemia in adults. Although hypoglycaemia is a well known adverse effect of antidiabetic agents, it may occasionally develop in the course of treatment with drugs used in everyday clinical practice, including NSAIDs, analgesics, antibacterials, antimalarials, antiarrhythmics, antidepressants and other miscellaneous agents. They induce hypoglycaemia by stimulating insulin release, reducing insulin clearance or interfering with glucose metabolism. Several drugs may also potentiate the hypoglycaemic effect of antidiabetic agents. Administration of these agents to individuals with diabetes mellitus is of most concern. Many of these drugs, and depending on clinical setting, may also induce hyperglycaemia. Drug-induced hepatotoxicity and nephrotoxicity may lead in certain circumstances to hypoglycaemia. Some drugs may also induce hypoglycaemia by causing pancreatitis. Drug-induced hypoglycaemia is usually mild but may be severe. Effective clinical management can be handled through awareness of this drug-induced adverse effect on blood glucose levels. Herein, we review pertinent clinical information on the incidence of drug-induced hypoglycaemia and discuss the underlying pathophysiological mechanisms, and prevention and management.

[Long-term malaria prophylaxis with mefloquine: a study of adverse drug reactions]

PURPOSE

To estimate the relative frequency of reported adverse drug reactions during the malaria chemoprophylactic period of the Moroccan contingent in Democratic Republic of Congo (DRC).

METHODS

The transversal survey involved all military personnel of the Moroccan contingent and was carried out using a questionnaire to be filled out by a multidisciplinary medical team. It was performed in all the military sites and the advanced posts accessible during the period of the study.

RESULTS

The study involved 362 male military subjects. Ninety-four adverse drug reactions were described: neuropsychiatric (anxiety, irritability, dizziness...) [n=76], digestive (anorexia, diarrhea, nausea...) [n=42], cardiovascular (tachycardia, palpitation, precordialgia...) [n=5], musculoskeletal (arthralgia, cramps) [n=4], cutaneous (redness, purpura) [n=2], and other (n=13). No "unexpected" or "serious" adverse drug reaction was reported. The causality assessment score was determined in 94 cases. Two of these reports were rated "likely", 12 "possible" and 80 doubtful. More adverse drug reactions were reported by subjects having medical and paramedical functions.

CONCLUSION

During our study, mefloquine induced adverse drug reactions in a quarter of the treated subjects. Most of the adverse drug reactions were neuropsychiatric. No "serious" adverse drug reactions were reported underlying the interest of its use, even for long-term chemoprophylaxis.

Effects of anti-malarial drugs on the electrocardiographic QT interval modelled in the isolated perfused guinea pig heart system

BACKGROUND

Concern over the potential cardiotoxicity of anti-malarial drugs inducing a prolonged electrocardiographic QT interval has resulted in the almost complete withdrawal from the market of one anti-malarial drug - halofantrine. The effects on the QT interval of four anti-malarial drugs were examined, using the guinea pig heart.

METHODS

The guinea pig heart was isolated, mounted on a Langendorff apparatus, and was then perfused with pyruvate-added Klebs-Henseleit solutions containing graded concentrations of the four agents such as quinidine (0.15 - 1.2 μM), quinine (0.3 - 2.4 μM), halofantrine (0.1 - 2.0 μM) and mefloquine (0.1 - 2.0 μM). The heart rate-corrected QaTc intervals were measured to evaluate drug-induced QT prolongation effects.

RESULTS

Quinidine, quinine, and halofantrine prolonged the QaTc interval in a dose-dependent manner, whereas no such effect was found with mefloquine. The EC50 values for the QaTc prolongation effects, the concentration that gives a half-maximum effect, were quinidine < quinine ≈ halofantrine.

CONCLUSIONS

In this study, an isolated, perfused guinea pig heart system was constructed to assess the cardiotoxic potential of anti-malarial drugs. This isolated perfused guinea pig heart system could be used to test newly developed anti-malarial drugs for their inherent QT lengthening potential. More information is required on the potential variation in unbound drug concentrations in humans, and their role in cardiotoxicity.

Mefloquine neurotoxicity: a literature review

A literature review revealed that mefloquine neurotoxicity has been demonstrated at both the preclinical and clinical levels, with nausea, dizziness, sleep disturbances, anxiety and psychosis, amongst other adverse neuropsychiatric events, reported in users. Females and individuals of low body mass index (BMI) are at apparent greater risk. Mechanisms of possible neurotoxicity may include binding to neuroreceptors and cholinesterases, inhibition of sarcoendoplasmic reticulum ATPase (SERCA) and interference with cellular Ca(2+) homeostasis, accumulation in the CNS, and reductions in CNS efflux in individuals possessing certain MDR1 polymorphisms. It may be prudent to avoid mefloquine in females and low BMI individuals, and in combination with other potentially neurotoxic agents such as the artemisinin antimalarials.

Proarrhythmic potential of antimicrobial agents

Several antiarrhythmic and non-cardiovascular drug therapies including antimicrobial agents have been implicated as the causes for QT interval prolongation, torsades de pointes (TdP) ventricular tachycardia and sudden cardiac death. Most of the drugs that have been associated with the lengthening of the QT interval or development of TdP can also block the rapidly activating component of the delayed rectifier potassium current (IKr) in the ventricular cardiomyocytes. This article presents a review of the current literature on the QT interval prolonging effect of antimicrobials based on the results of the in vitro, in vivo studies and case reports. Our observations were derived from currently available Medline database. As we found, the most frequently QT interval prolonging antimicrobials are erythromycin, clarithromycin, fluoroquinolones, halofantrine, and pentamidine. Almost every antimicrobial-associated QT interval prolongation occurs in patients with multiple risk factors of the following: drug interactions, female gender, advanced age, structural heart disease, genetic predisposition, and electrolyte abnormalities. In conclusion, physicians should avoid prescribing antimicrobials having QT prolonging potential for patients with multiple risk factors. Recognition and appropriate treatment of TdP are also indispensable.

WITHDRAWN: Mefloquine for preventing malaria in non-immune adult travellers

BACKGROUND

Mefloquine is commonly prescribed to prevent malaria in travellers, and has replaced other drugs because Plasmodium falciparum is commonly resistant to them. However, mefloquine may be associated with neuropsychiatric harmful effects.

OBJECTIVES

To assess the effects of mefloquine in adult travellers compared to other regimens in relation to episodes of malaria, withdrawal from prophylaxis, and adverse events.

SEARCH STRATEGY

We searched the Cochrane Infectious Diseases Group specialized trials register (September 2002), The Cochrane Central Register of Controlled Trials (The Cochrane Library Issue 3, 2002), MEDLINE (1966 to September 2002), EMBASE (1980 to September 2002), LILACS (September 2002), Science Citation Index (1981 to September 2002), and bibliographies in retrieved papers and standard textbooks. We contacted researchers in the subject of malaria chemoprophylaxis, and pharmaceutical companies.

SELECTION CRITERIA

Randomised trials comparing mefloquine with other standard prophylaxis or placebo in non-immune adult travellers, and in non-travelling volunteers. For adverse events, any published case reports were collected.

DATA COLLECTION AND ANALYSIS

We independently assessed trial quality and extracted data. Adverse events from observational studies were categorised by the study type. We also contacted study authors.

MAIN RESULTS

We included 10 trials involving 2750 non-immune adult participants. Five of these were field trials, and of these all were in mainly male soldiers. One trial comparing mefloquine with placebo showed mefloquine prevented malaria episodes in an area of drug resistance (Peto odds ratio 0.04, 95% confidence interval 0.02 to 0.08). Withdrawals in the mefloquine group were consistently higher in four placebo controlled trials (odds ratio 3.56, 95% confidence interval 1.67 to 7.60). In five trials comparing mefloquine with other chemoprophylaxis, no difference in tolerability was detected. We found 516 published case reports of mefloquine adverse effects. 63 per cent of these published reports involved tourists and business travellers. There were four fatalities attributed to mefloquine.

AUTHORS' CONCLUSIONS

Mefloquine prevents malaria, but has adverse effects that limit its acceptability . There is evidence from non-randomised studies that mefloquine has potentially harmful effects in tourists and business travellers, and its use needs to be carefully balanced against this. Trials of comparative effects of antimalarial prophylaxis should include episodes of malaria and withdrawal from prophylaxis as outcomes.

Modification of K+ channel-drug interactions by ancillary subunits

Reconciling ion channel alpha-subunit expression with native ionic currents and their pharmacological sensitivity in target organs has proved difficult. In native tissue, many K(+) channel alpha-subunits co-assemble with ancillary subunits, which can profoundly affect physiological parameters including gating kinetics and pharmacological interactions. In this review, we examine the link between voltage-gated potassium ion channel pharmacology and the biophysics of ancillary subunits. We propose that ancillary subunits can modify the interaction between pore blockers and ion channels by three distinct mechanisms: changes in (1) binding site accessibility; (2) orientation of pore-lining residues; (3) the ability of the channel to undergo post-binding conformational changes. Each of these subunit-induced changes has implications for gating, drug affinity and use dependence of their respective channel complexes. A single subunit may modulate its associated alpha-subunit by more than one of these mechanisms. Voltage-gated potassium channels are the site of action of many therapeutic drugs. In addition, potassium channels interact with drugs whose primary target is another channel, e.g. the calcium channel blocker nifedipine, the sodium channel blocker quinidine, etc. Even when K(+) channel block is the intended mode of action, block of related channels in non-target organs, e.g. the heart, can result in major and potentially lethal side-effects. Understanding factors that determine specificity, use dependence and other properties of K(+) channel drug binding are therefore of vital clinical importance. Ancillary subunits play a key role in determining these properties in native tissue, and so understanding channel-subunit interactions is vital to understanding clinical pharmacology.

Cardiotoxicity of antimalarial drugs

There are consistent differences in cardiovascular state between acute illness in malaria and recovery that prolong the electrocardiographic QT interval and have been misinterpreted as resulting from antimalarial cardiotoxicity. Of the different classes of antimalarial drugs, only the quinolines, and structurally related antimalarial drugs, have clinically significant cardiovascular effects. Drugs in this class can exacerbate malaria-associated orthostatic hypotension and several have been shown to delay ventricular depolarisation slightly (class 1c effect), resulting in widening of the QRS complex, but only quinidine and halofantrine have clinically significant effects on ventricular repolarisation (class 3 effect). Both drugs cause potentially dangerous QT prolongation, and halofantrine has been associated with sudden death. The parenteral quinoline formulations (chloroquine, quinine, and quinidine) are predictably hypotensive when injected rapidly, and cardiovascular collapse can occur with self-poisoning. Transiently hypotensive plasma concentrations of chloroquine can occur when doses of 5 mg base/kg or more are given by intramuscular or subcutaneous injection. At currently recommended doses, other antimalarial drugs do not have clinically significant cardiac effects. More information on amodiaquine, primaquine, and the newer structurally related compounds is needed.

Malaria: Diagnosis and treatment of falciparum malaria in travelers during and after travel

Plasmodium falciparum is responsible for most of the mortality in travelers related to imported malaria. Problems that occur during travel include the inaccuracy of a microscopic diagnosis of malaria, both false positives and false negatives, when ill travelers seek care while abroad. A false positive diagnosis can result in unnecessary parenteral injections that carry a risk of transmission of blood-borne pathogens, receipt of potentially dangerous drugs such as halofantrine, or receipt of fake, counterfeit drugs. Increased morbidity and mortality are associated with delays in diagnosis and initiation of prompt treatment for falciparum malaria. Availability of expert microscopy to confirm the diagnosis of malaria is limited. The presence of splenomegaly and thrombocytopenia are strongly associated with malaria and would justify empiric treatment. The availability of atovaquone-proguanil, a safe and well tolerated oral drug, should prompt a reconsideration of current treatment recommendations that discourage empiric treatment on clinical suspicion alone.

Safety evaluation of fixed combination piperaquine plus dihydroartemisinin (Artekin) in Cambodian children and adults with malaria

AIMS

To assess the haemodynamic, electrocardiographic and glycaemic effects of piperaquine-dihydroartemisinin (Artekin) fixed combination therapy in uncomplicated malaria.

METHODS

Sixty-two Cambodians (32 children and 30 adults) with falciparum or vivax malaria were given Artekin given as four age-based oral doses over 32 h. Supine and erect blood pressure, the electrocardiographic QT interval and plasma glucose were measured before treatment and then at regular intervals during a 4-day admission period as part of efficacy and safety monitoring. QT intervals were rate-corrected (QTc) using Bazett's formula.

RESULTS

Artekin therapy was well tolerated and all patients responded to treatment. Average parasite and fever clearance times were 19 and 12 h, respectively. The pretreatment mean fall in systolic blood pressure on standing was 8 +/- 6 mmHg and 6-hourly measurements over 72 h showed no significant change (P = 0.48). There was a significant lengthening of the mean QTc to a maximum of 11 ms(0.5) (95% confidence interval 4-18 ms(0.5)) relative to baseline at 24 h (P = 0.003). The maximal QTc prolongation observed in any patient was 53 ms(0.5). There was a mean 0.4 mmol l(-1) reduction in the post-absorptive plasma glucose during the first 48 h but no episodes of hypoglycaemia (plasma glucose < 3.0 mmol l(-1)) were observed at any time.

CONCLUSIONS

Artekin is safe and effective combination therapy for uncomplicated malaria in children and adults. Although piperaquine is a long half-life drug related to other quinoline compounds including chloroquine and quinine, no clinically significant cardiovascular or metabolic effects were observed.

La méfloquine chez le nourrisson et l’enfant lors de l’accès palustre simple à Plasmodium falciparum : un traitement efficace et bien toléré

OBJECTIVES

The aim of this study was to evaluate the efficacy and tolerance of mefloquine treatment in children, especially in infants of less than 15 kg, in an endemic area of malaria (French Guiana).

METHOD

This 5-years (1996-2000) retrospective study included 61 children aged 6 months to 16 years who had been treated with mefloquine for acute Plasmodium falciparum malaria. Twenty-six of these children weighted less than 15 kg. The efficiency of the treatment was evaluated using clinical and parasitic data that had been validated according to the criteria of the World Health Organization (WHO). Tolerance was compared with the data in the medical literature.

RESULTS

None of the 59 patients who were given the treatment correctly presented signs of early therapeutic failure as defined by the WHO. Apyrexia was obtained in 48 h on average (CI 95%: 39-57; median: 36 h). The mean time required to obtain negative parasitism was 91 h (CI 95%: 80-101; median: 96 h) among the 51 patients in whom this was measured. Mild side effects were observed in 27.8% of the cases affecting mainly the digestive system. No differences were observed regarding efficacy or tolerance for children who weighed less than 15 kg.

CONCLUSION

Mefloquine represents an efficient treatment for acute uncomplicated P. falciparum malaria in children and is well-tolerated even in infants.

[Efficacy and tolerance of mefloquine in the treatment of infants and children with Plasmodium falciparum malaria]

Only a limited number of treatments are available for use in young children with malaria.

OBJECTIVES

The aim of this study was to evaluate the efficacy and tolerance of mefloquine treatment in children, especially in infants of less than 15 kg, in an endemic area of malaria (French Guiana).

METHOD

This five-years (1996-2000) retrospective study included 61 children aged six months to 16 years who have been treated with mefloquine for acute P. falciparum malaria. Twenty-six of these children weighted less than 15 kg. The efficiency of the treatment was evaluated using clinical and parasitic data that had been validated according to the criteria of the World Health Organization (WHO). Tolerance was compared with the data in the medical literature.

RESULTS

None of the 59 patients who were given the treatment correctly presented signs of early therapeutic failure as defined by the WHO. Apyrexia was obtained in 47.8 h on average (CI 95%: 39-57; median: 36 h). The mean time required to obtain negative parasitism was 90.8 h (CI 95%: 80-101; median: 96 h) among the 51 patients in whom this was measured. Mild side effects were observed in 27.8% of the cases affecting mainly the digestive system. No differences were observed regarding efficacy or tolerance for children who weighed less than 15 kg.

CONCLUSION

Mefloquine represents an efficient treatment for acute uncomplicated P. falciparum malaria in children and is well tolerated even in infants.

Synthesis and biological evaluation of new imidazo[1,2-a]pyridine derivatives designed as mefloquine analogues

This paper describes the synthesis and the in vitro antimalarial profile of two new imidazo[1,2-a]pyridine derivatives 4HCl and 13HCl, structurally proposed as mefloquine (1) analogues, by exploring bioisosterism and molecular simplification tools. The synthetic route employed to access the title compounds used, as starting material, the previously described ethyl 2-methylimidazo[1,2-aJpyridine-3-carboxylate derivative (5). These novel heterocyclic derivatives 4HCl and 13HCl presented modest antimalarial activity against the W-2 and D-6 clones of Plasmodium falciparum as well as inhibitors of in vitro heme polymerization compared to mefloquine.

The inhibition of gluconeogenesis by chloroquine contributes to its hypoglycaemic action

The effect of chloroquine on gluconeogenesis in isolated hepatocytes and kidney-cortex tubules of rabbit has been studied. The inhibitory action of 200 microM chloroquine was the highest in hepatocytes and renal tubules incubated with glutamine and glutamate+glycerol+octanoate, respectively, while in the presence of other substrates the drug action was less pronounced. With amino acids as substrates, the inhibition of gluconeogenesis was accompanied by a decreased glutamine production, resulting from a decline of glutamate dehydrogenase activity. A decrease in the urea production by hepatocytes incubated with chloroquine in the presence of glutamine but not NH4Cl as the source of ammonium is in agreement with this suggestion. The degree of inhibition by chloroquine of the rate of gluconeogenesis in renal tubules isolated from control rabbits was similar to that determined in diabetic animals. Chloroquine-induced changes in levels of intracellular gluconeogenic intermediates indicate a decrease in phosphoenolpyruvate carboxykinase and glucose-6-phosphatase activities probably due to increased concentration of 2-oxoglutarate, an inhibitor of these two enzymes. In view of the data, it is likely that inhibition by chloroquine of glucose formation in liver and kidney may contribute to the hypoglycaemic action of this drug. The importance of the inhibitory effect of chloroquine on glutamate dehydrogenase activity in the antihyperglycaemic action of the drug is discussed.

Coadministration of mefloquine and chloroqine: use of a pharmacokinetic-based approach to reduce toxicity

A child with malaria from a chloroquine-resistant area received an accidental overdose of chloroquine administered by a parent. Application of pharmacokinetics permitted definitive treatment with mefloquine in a safe and effective manner.

Potentiation of halofantrine-induced QTc prolongation by mefloquine: correlation with blood concentrations of halofantrine

1. The antimalarial drug halofantrine can prolong the QT interval and this may be enhanced by prior use of mefloquine. This possible interaction has been investigated by examining the effects of halofantrine and mefloquine alone and in combination. 2. In anaesthetized rabbits (n=6 per group), halofantrine given as bolus doses of 1, 3, 10, and 30 mg kg(-1) at 25 min intervals dose-dependently prolonged the rate-corrected QT (QTc) interval from 313+/-12 ms pre-drug to 410+/-18 ms after the highest dose. Similar doses of mefloquine did not alter QTc intervals significantly. The highest dose of mefloquine (30 mg kg(-1)) caused cardiac contractile failure. 3. Pretreatment with 3 mg kg(-1) mefloquine 25 min before the first dose of halofantrine potentiated the effects of all doses of halofantrine on QTc intervals. 4. The blood concentrations of halofantrine were two to six times higher in the group pretreated with mefloquine compared to the halofantrine alone group; e.g. 1.03+/-0.17 and 0.16+/-0.02 microM respectively after 1 mg kg(-1) halofantrine. There was a significant correlation between blood halofantrine concentrations and QTc intervals (r=0.673). Even after making allowance for overestimation of the potency of halofantrine that may result from the hypokalaemia that is prevalent in anaesthetized rabbits, these effects occurred with concentrations of halofantrine that are found in clinical use. 5. These data indicate clearly that while mefloquine does not alter QTc intervals itself, it does enhance the effects of halofantrine by increasing the circulating concentration of halofantrine.

Pharmacokinetic interaction trial between co-artemether and mefloquine

Forty-two healthy subjects were randomized in a parallel three-group design trial to investigate potential electrocardiographic and pharmacokinetic interactions between the new antimalarial co-artemether, a combination of artemether and lumefantrine (both of which are predominantly metabolized through CYP3A4), and mefloquine, another antimalarial described as a substrate (and possible inhibitor) of CYP3A4. Subjects were assigned to one of the three possible treatment groups (i.e., co-artemether alone or mefloquine alone or the combination of both). The dosage was 1000 mg mefloquine (divided into three doses over 12 h) followed 12 h later by six applications of co-artemether (40 mg artemether+480 mg lumefantrine each) over 60 h. The study medications were generally well tolerated after all treatments. Concomitant administration with mefloquine caused statistically significant lower (around 30-40%) plasma concentrations of lumefantrine than when co-artemether was administered alone. Even if important, this decrease in lumefantrine exposure was considered unlikely to impact clinical efficacy given the wide therapeutic index of co-artemether and the usual high variability in lumefantrine plasma levels, mostly and more importantly influenced by food intake. However, patients should be encouraged to eat at dosing times to compensate for this decreased bioavailability. The pharmacokinetics of artemether, DHA or mefloquine were not affected. Artemether concentrations significantly decreased over doses, independently of mefloquine co-administration, while DHA concentrations slightly (not significantly) increased. Therefore, no clinically relevant risks due to pharmacokinetic drug-drug interaction are expected at the enzymatic level following co-administration of co-artemether with CYP3A4 substrates with similar affinity to that of mefloquine.

Mefloquine for preventing malaria in non-immune adult travellers

OBJECTIVES

Mefloquine has now largely replaced earlier malaria prophylaxis drugs which are no longer considered to be effective against all Plasmodium species, due to parasite resistance. However mefloquine may be associated with neuropsychological harmful effects. The objective of this review was to assess the effects of mefloquine in adult travellers.

SEARCH STRATEGY

We searched the Cochrane Infectious Diseases Group trials register, Medline, Embase, Lilacs, Science Citation Index and reference lists of articles. We contacted researchers in the subject of malaria chemoprophylaxis, and drug companies.

SELECTION CRITERIA

Randomised trials comparing mefloquine with other standard prophylaxis or placebo in non-immune adult travellers.

DATA COLLECTION AND ANALYSIS

The two reviewers independently assessed trial quality and extracted data. Study authors were also contacted.

MAIN RESULTS

Ten trials involving 2750 non-immune adult travellers were included. One trial comparing mefloquine with placebo showed mefloquine prevented malaria episodes in an area of drug resistance (odds ratio 0.04, 95% confidence interval 0.02 to 0.08). Withdrawals in the mefloquine group were consistently higher in four placebo controlled trials (odds ratio 3. 56, 95% confidence interval 1.67 to 7.60). In five trials comparing mefloquine with other chemoprophylaxis, no difference in tolerability was detected.

REVIEWER'S CONCLUSIONS

Mefloquine prevents malaria, but there is not enough evidence to evaluate its tolerability and toxicity, particularly for general travellers.

Effects of mefloquine on cardiac contractility and electrical activity in vivo, in isolated cardiac preparations, and in single ventricular myocytes

1. To examine the possible cardiotoxicity of the antimalarial drug mefloquine, increasing doses (0.3 - 30 mg kg(-1)) were given i.v. to anaesthetized guinea-pigs. Mefloquine did not alter ECG intervals significantly but gradually increased systolic blood pressure (at 3 mg kg(-1)) then had a depressor effect (at 10 mg kg(-1)). Death due to profound hypotension, probably resulting from cardiac contractile failure or AV block, occurred after either 10 mg kg(-1) (2/6) or 30 mg kg(-1) (4/6) mefloquine. 2. In isolated cardiac preparations mefloquine (3 - 100 microM) did not alter the effective refractory period but at the higher concentrations resting tension increased. Developed tension was reduced by 100 microM mefloquine in left atria (from 5.8+/-1.7 to 2.2+/-0.4 mN) whereas in papillary muscles although 30 microM mefloquine reduced developed tension (from 2. 6+/-0.5 to 1.1+/-0.1 mN) subsequent addition of 100 microM caused a marked, but not sustained, positive inotropic effect (from 1.2+/-0.1 to 3.8+/-0.8 mN). 3. In single ventricular myocytes, mefloquine (10 microM) shortened action potential duration (e.g. APD(90) from 285+/-29 to 141+/-12 ms) and reduced the amplitude of the systolic Ca(2+) transient. 4. These effects were accompanied by a decrease in the L-type Ca(2+) current. These results indicate that the main adverse effect of mefloquine on the heart is a negative inotropic action. This action can be explained by blockade of L-type Ca(2+) channels.

Mefloquine for malaria chemoprophylaxis 1992-1998: a review

Mefloquine is an orally administered blood schizontocide for the chemoprophylaxis of malaria in nonimmune travelers. New pharmacokinetic data has shown that food increases the bioavailability of mefloquine. Steady-state pharmacokinetics of weekly prophylaxis in long term travelers have shown that toxic accumulation does not occur and that weekly dosing is associated with protective levels of the drug. The pharmacokinetics of mefloquine are highly stereospecific and all pharmacokinetic parameters, except tmax are significantly different for the (+) and (-) enantiomers. Mefloquine and its metabolite are not appreciably removed by hemodialysis. Steady-state levels of mefloquine can be attained in a reduced time frame of 4 days compared to 7-9 weeks using a loading dose strategy of 250 mg mefloquine daily for 3 days followed thereafter by weekly mefloquine dosage. This strategy, is however, associated with a higher incidence of an adverse event (AE). Cumulative evidence suggests a high protective efficacy of mefloquine (>91%) in nonimmune travelers to areas of chloroquine resistant Plasmodium falciparum (CRPF) except for clearly defined regions of multi-drug resistance. Reports from sub-Saharan Africa indicate a low but increasing level of resistance to this drug. Mefloquine resistance is associated with halofantrine and quinine resistance but not with chloroquine resistance. Penfluridol has been shown to reverse P. falciparum mefloquine resistance in vitro. There is some controversy regarding the tolerabilty of mefloquine for malaria chemoprophylaxis. A review of the studies conducted during 1992-1998 shows that in the reporting of any AE the incidence lies in the range (12-90%) and where there is a comparator, is equivalent to the incidence reported for almost all alternative regimens. When some measure of subjective severity is applied to the rating of AE, it appears that 11-17% of travelers are, to some extent, incapacitated by AE. Major studies and worldwide monitoring have shown that serious events are rare. A recent meta-analysis showed that rates of withdrawal and overall incidence of AE with mefloquine were not significantly higher than those observed with comparator regimens except that mefloquine was more likely to cause insomnia and fatigue. Withdrawals in mefloquine arms were higher than in placebo arms. No performance deficit or functional impairment was observed in five clinical toxicity studies of mefloquine prophylaxis, including a study of driving performance. There is limited data regarding use of mefloquine in pregnancy. Early animal studies have documented teratogenic and embryotoxic effects associated with the use of high dose mefloquine. Two studies have shown a relatively high incidence of spontaneous abortions in mefloquine users. Cumulative evidence, however, is reassuring and has led the World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC) to sanction the use of mefloquine in pregnant women during the second and third trimesters. In conclusion, mefloquine prophylaxis is recommended for travelers to high risk areas of chloroquine resistant Plasmodium falciparum. The risk of malarial infection and the proven efficacy of mefloquine to prevent malaria should be weighed against the risk of drug associated adverse events.

Malaria in travelers. Epidemiology, disease, and prevention

The combination of increases in international travel and escalating drug resistance has resulted in a growing number of travelers contracting malaria. Preventing malaria-associated morbidity and mortality will require improved health information for travelers about the risk of malaria and appropriate preventive measures, improved recognition of infection by physicians, rapid and accurate laboratory diagnosis, and prompt initiation of effective therapy.