Risks and benefits of prophylactic antimalarial drugs

Development of antimalarial drugs and their application in China: a historical review

This historical review covers antimalarials developed in China, which include artemisinin, artemether, artesunate, and dihydroartemisinin, as well as other synthetic drugs such as piperaquine, pyronaridine, benflumetol (lumefantrine), and naphthoquine. The curative effects of these antimalarials in the treatment of falciparum malaria, including chloroquine-resistant strain, are especially discussed. Following the World Health Organization (WHO) recommended artemisinin-based combination therapy (ACT), different combinations of artemisinin, or its derivative, along with another antimalarial drug were orally used to treat Plasmodium falciparum infections. The recrudescence rates were low, gametocyte carriers lessened, and the curative rate increased remarkably. The combination therapy effectively deferred the emergence of drug resistance in the parasite. The regulation "The guidelines and regimens for the use of antimalarial drugs in China" was issued to guide rational application and standardize malaria treatment in the country. As the recommended first-line drug to treat falciparum malaria in the world, ACT was adopted in the regulation. In response to the global initiative of malaria eradication proposed by the UN Millennium Development Goals (MDGs), the Chinese government has set a target to eliminate malaria by 2020.

Malaria chemoprophylaxis of 3,446 French travelers departing from Paris to eight tropical countries

BACKGROUND

Each year more and more French travelers are visiting areas where malaria is endemic. The aim of this study was to assess prophylactic regimens used by French travelers and to determine whether they meet current published recommendations.

METHODS

This 12 month transversal study (May 1, 1995 to April 31, 1996) was conducted in embarkment lounges of Roissy Charles de Gaulle Airport to eight "tropical" destinations.

RESULTS

3,446 French travelers were enrolled. Twenty two and three-fifths percent of travelers had not sought any advice. The percentages of travelers staying less than 3 months (n = 2899) at risk of malaria (i.e., using none or inadequate chemoprophylaxis) were, according to the destination: Brazil (20%), Gabon (83%), Ivory Coast (26%), Kenya (43%), Madagascar (39%), Thailand (22%), Venezuela (41%) and Vietnam (8%). The suitability of the prophylaxis according to the information source for travelers staying less than 3 months varied as follows: specialist physician (OR = 1), travel agent (OR = 1.01, CI = 0.9 - 1. 1), occupational physician (OR = 1.13, CI = 0.6 - 2.1), GP (OR = 1. 58, CI = 1.1 - 2.3), none (OR = 1.95, CI = 1.3 - 2.9), friends (OR = 3, CI = 1.8 - 5) and pharmacist (OR = 3.94, CI = 2.1 - 7.5). Suitability of prophylaxis also varied according to the type of trip: organized tour (OR = 1), business trip (OR = 1.04, CI = 0.8 - 1.4), adventure tourism (OR = 2.1, CI = 1.6 - 2.9) and visit to family or friends (OR = 2.3, CI = 1.7 - 3.1).

CONCLUSIONS

This study shows that the quality of advice on antimalarial chemoprophylaxis varies markedly according to the source, and that nearly one in three French travelers (29.3 %, 850/2899) to tropical areas is at risk of malaria.

[Mefloquine chemoprophylaxis of malaria in the Brazilian Amazonia]

In a randomised double-blind study 122 volunteers living in an endemic malarious area in Amazonian Rondônia state were divided into 4 groups to study malaria suppression. . The first group received 500 mg of mefloquine every month, group II 250 mg every two weeks, group III a tablet of Fansidar (500 mg sulphadoxine + 25mg pyrimethamine) a week and group IV placebo. Acute attacks of malaria occurred in one individual in group I, 2 subject in group II, and 6 individuals in groups III and IV. Protection with mefloquine was significant compared with the placebo group. Both treatment regimens with mefloquine were effective suppressants in an area of high prevalence of drug multiresistant Plasmodium falciparum transmission.

Steady state pharmacokinetics of mefloquine in long-term travellers

Mefloquine is an antimalarial drug with a 3-week elimination half-life, which has led to concerns that toxic accumulation may occur during weekly administration for long-term malaria chemoprophylaxis. Despite the endorsement of weekly mefloquine by the World Health Organization and the United States Centers for Disease Control, mefloquine pharmacokinetics have been incompletely studied in subjects taking the drug once weekly for more than 4 weeks. Our objective was to study plasma mefloquine concentrations in travelers taking mefloquine 250 mg once weekly for 3 months. Multiple mefloquine concentrations were measured by high pressure liquid chromatography following the 1st, 2nd and 10th to 13th of 13 weekly doses of 250 mg mefloquine taken by 15 Canadian travellers (median age 23 years; 6 male, 14 white). Steady state was achieved in all subjects by or before the 10th dose. Mefloquine pharmacokinetic values were comparable to those previously reported by other investigators. In 7 subjects, 2 peaks of mefloquine and metabolite concentration followed ingestion, suggesting redistribution of mefloquine. Mefloquine concentration 14 d after the last dose was 74% of the level 7 d after the last dose. In conclusion, pharmacokinetic values determined by this study support mefloquine weekly dosing for long-term malaria chemoprophylaxis; toxic accumulation does not occur and weekly dosing is associated with significantly higher trough levels than 14 d dosing.

Malaria: protection of the international traveler

Thorough counseling with emphasis on the importance of mosquito bite avoidance, as well as on compliance with prophylactic antimalarial regimens, remains an important task for the physician preparing a patient for international travel. Chloroquine continues to be the drug of choice for prophylaxis in areas not reporting chloroquine resistance. Otherwise, mefloquine is the first-line agent. Under special circumstances, alternatives to mefloquine can be employed and include doxycycline or proguanil plus chloroquine.