Fatty food does not alter blood mefloquine concentrations in the treatment of falciparum malaria

Australian Defence Force Global Health Engagement through malaria and other vectorborne disease programmes in the Pacific and Southeast Asia

Global Health Engagement is one method employed by the Australian Defence Force (ADF) in pursuit of its objectives to shape Australia's strategic environment and to deter actions against Australia's interests. Two recent examples of such engagements are malaria mitigation programmes led by the ADF Malaria and Infectious Disease Institute in partnership with the Vietnam People's Army and the Papua New Guinea Defence Force. Both programmes were designed with extensive collaboration with host nation stakeholders, empowered local institutions and governance systems, built the capacity of the host nation with the aim of achieving independence from Australian support and met the strategic policy requirements of all nations involved. Process and outcome measures were built into both programmes, providing partner nations with the necessary assurance that funding was being used effectively. The long-term nature of each programme engendered personal trust between individuals and cultural understanding between military units. Recognising the value of formal education in the design and conduct of such programmes, ADF officers participate as students and instructors in the US Uniformed University of the Health Sciences course in Global Health and Global Health Engagement. Critically, this educational opportunity is afforded to future leaders in all professions related to health, including clinicians, military health planners and commanders. While an essential prerequisite to Global Health Engagement Programmes is their technical viability and validity, the most important key to success in the military context is a widespread understanding of how they achieve desired strategic effects for all involved.

Population pharmacokinetics and pharmacodynamics of the artesunate-mefloquine fixed dose combination for the treatment of uncomplicated falciparum malaria in African children

Background

The World Health Organization (WHO) recommends combinations of an artemisinin derivative plus an anti-malarial drug of longer half-life as treatment options for uncomplicated Plasmodium falciparum infections. In Africa, artesunate–mefloquine (ASMQ) is an infrequently used artemisinin-based combination therapy (ACT) because of perceived poor tolerance to mefloquine. However, the WHO has recommended reconsideration of the use of ASMQ in Africa. In this large clinical study, the pharmacokinetics (PK) of a fixed dose combination of ASMQ was investigated in an African paediatric population to support dosing recommendations used in Southeast Asia and South America.

Methods

Among the 472 paediatric patients aged 6–59 months from six African centres included in the large clinical trial, a subset of 50 Kenyan children underwent intensive sampling to develop AS, its metabolite dihydroartemisinin (DHA) and MQ PK models. The final MQ PK model was validated using sparse data collected in the remaining participants (NONMEM^®). The doses were one or two tablets containing 25/55 mg AS/MQ administered once a day for 3 days according to patients’ age. A sensitive LC–MS/MS method was used to quantify AS, DHA and MQ concentrations in plasma. An attempt was made to investigate the relationship between the absence/presence of malaria recrudescence and MQ area under the curve (AUC) using logistic regression.

Results

AS/DHA concentration–time profiles were best described using a one-compartment model for both compounds with irreversible AS conversion into DHA. AS/DHA PK were characterized by a significant degree of variability. Body weight affected DHA PK parameters. MQ PK was characterized by a two-compartment model and a large degree of variability. Allometric scaling of MQ clearances and volumes of distribution was used to depict the relationship between MQ PK and body weight. No association was found between the model predicted AUC and appearance of recrudescence.

Conclusions

The population pharmacokinetic models developed for both AS/DHA and MQ showed a large variability in drug exposure in the investigated African paediatric population. The largest contributor to this variability was body weight, which is accommodated for by the ASMQ fixed dose combination (FDC) dosing recommendation. Besides body weight considerations, there is no indication that the dosage should be modified in children with malaria compared to adults.

Trial registration Pan African Clinical Trials Registry PACTR201202000278282 registration date 2011/02/16

Electronic supplementary material

The online version of this article (10.1186/s12936-019-2754-6) contains supplementary material, which is available to authorized users.

Formulation and evaluation of Pheroid vesicles containing mefloquine for the treatment of malaria

OBJECTIVES

Mefloquine (MQ) is an antimalarial drug with high efficacy, often used in the treatment and chemoprophylaxis of malaria. However, it has low solubility in water, a long elimination half-life (4 days), and is neurotoxic, which leads to unwanted side effects.

METHODS

We investigated a lipid-based drug delivery system, Pheroid vesicles, in combination with MQ (Pheroid MQ), to promote future clinical use. MQ was incorporated into Pheroid vesicles and the formulations characterized. The formulations were evaluated in terms of in-vitro efficacy and toxicity. In-vivo bioavailability studies were conducted in C57 BL6 mice.

KEY FINDINGS

The vesicles incorporated MQ with ~63% entrapment efficiency. The IC50 values of MQ after 48-h incubation in chloroquine-resistant (RSA11) and chloroquine sensitive (3D7) strains, were reduced by ~50% and ~30% respectively. In-vivo bioavailability study revealed no change in the pharmacokinetic parameters of MQ, and the incorporation of the drug in Pheroid vesicles reduced the in-vitro haemolytic activity by ~75%. Furthermore, the cytotoxicity against human neuroblastoma cells (SH-SY5Y) of the free drug was reduced by ~64% with Pheroid MQ.

CONCLUSIONS

Pheroid vesicles may therefore decrease the toxicity of MQ and thereby improve its therapeutic index, a strategy that may provide an effective alternative for malaria chemoprophylaxis and treatment.

Clinical pharmacology of artemisinin-based combination therapies

Malaria, a disease transmitted by the female Anopheles mosquito, has had devastating effects on human populations for more than 4000 years. Treatment of the disease with single drugs, such as chloroquine, sulfadoxine/pyrimethamine or mefloquine, has led to the emergence of resistant Plasmodium falciparum parasites that lead to the most severe form of the illness. Artemisinin-based combination therapies are currently recommended by WHO for the treatment of uncomplicated P. falciparum malaria. Artemisinin and semisynthetic derivatives, including artesunate, artemether and dihydroartemisinin, are short-acting antimalarial agents that kill parasites more rapidly than conventional antimalarials, and are active against both the sexual and asexual stages of the parasite cycle. Artemisinin fever clearance time is shortened to 32 hours as compared with 2-3 days with older agents. To delay or prevent emergence of resistance, artemisinins are combined with one of several longer-acting drugs--amodiaquine, mefloquine, sulfadoxine/pyrimethamine or lumefantrine--which permit elimination of the residual malarial parasites. The clinical pharmacology of artemisinin-based combination therapies is highly complex. The short-acting artemisinins and their long-acting counterparts are metabolized and/or inhibit/induce cytochrome P450 enzymes, and may thus participate in drug-drug interactions with multiple drugs on the market. Alterations in antimalarial drug plasma concentrations may lead to either suboptimal efficacy or drug toxicity and may compromise treatment.

Population pharmacokinetics of mefloquine in military personnel for prophylaxis against malaria infection during field deployment

OBJECTIVE

The purpose of this study was to determine the population pharmacokinetics of mefloquine in healthy military personnel during prophylaxis for malaria infections.

METHODS

The subjects were 1,111 Australian soldiers participating in two studies: a randomised double-blinded study (group A, 161 subjects) and an open-label study (group B, 950 subjects). Following a loading dose (250 mg mefloquine base daily, 3 days), subjects received an oral weekly maintenance dose of 250 mg over 6 months. Blood was collected after the last split loading dose then at weeks 4, 8 and 16 for group A, and at weeks 13 and 26 for group B. Plasma mefloquine concentrations were measured by high-performance liquid chromatography (HPLC). Pharmacokinetic modelling was performed using NONMEM.

RESULTS

A two-compartment model with inter-occasion variability (IOV) for clearance satisfactorily described the pharmacokinetics. Typical values were clearance (CL/F, 2.09 l/h), central volume of distribution (V1/F, 528 l), absorption rate constant (KA, 0.24 h(-1)), inter-compartmental clearance (Q/F, 12.5 l/h), peripheral volume of distribution (V2/F, 483 l) and elimination half-life (t (1/2), 14.0 days). Weight had a positive influence on central volume but was insufficient to warrant dosage adjustments. The inter-individual variability (coefficient of variation, CV%) for CL/F and V1/F was 24.4% and 29.6%, respectively. The IOV for CL/F was 17.8%. The proportional residual error (CV%) for groups A and B was 11.5% and 19.5%, respectively, and the additive error standard deviation (SD) was 57 ng/ml and 149 ng/ml, respectively.

CONCLUSION

The typical parameter values were comparable with those estimated in much smaller cohorts of healthy subjects and in malaria patients treated with single-dose mefloquine. The lower unexplained variability in the blinded study suggested these subjects may have been more compliant in taking their medication than soldiers in the open-label study.