What are the guidelines for using antimalarial drugs?

Guidelines for Using Antimalarial Drugs

The selection of appropriate antimalarial drugs should be based on the geographic area of travel, patient characteristics, and drug resistance patterns, with chloroquine remaining the standard prophylaxis in areas without resistance, while mefloquine, doxycycline, or combination therapies are recommended for areas with chloroquine-resistant Plasmodium falciparum. 1

Key Principles of Antimalarial Prophylaxis

• Compliance is essential for effective prophylaxis; most malaria deaths occur in those who do not fully comply with the recommended regimen 1
• Start chemoprophylaxis 1-2 weeks before travel to malarious areas (except doxycycline, which can begin 1-2 days before) to establish adequate blood levels and assess for potential side effects 1
• Continue prophylaxis during travel in malarious areas and for 4 weeks after leaving (except mefloquine, which requires only two additional doses after leaving the area) 1
• Store all antimalarial medications in child-proof containers out of children's reach, as overdose can be fatal 1

Drug Selection Based on Resistance Patterns

For Areas Without Chloroquine Resistance:

• Chloroquine 300 mg base weekly is the standard prophylaxis 1
• Well-tolerated with rare serious adverse reactions at prophylactic doses 1, 2
• Minor side effects (gastrointestinal disturbance, dizziness) are typically transient and self-limited 1

For Areas With Chloroquine-Resistant P. falciparum:

• Mefloquine alone is recommended as first-line prophylaxis 1
• In areas with limited to moderate chloroquine resistance, chloroquine plus daily proguanil provides substantial protection, though less than mefloquine 1
• Doxycycline is an alternative for short-term travelers who cannot take mefloquine 1
• For areas with mefloquine-resistant falciparum malaria (East Asia), doxycycline is becoming increasingly useful 1

Special Populations Considerations

Children:

• Children of any age can contract malaria and require appropriate prophylaxis 1
• Mefloquine is contraindicated in children weighing less than 15 kg (30 lbs) 1
• Doxycycline is contraindicated in children less than 8 years of age 1
• Pediatric doses should be calculated carefully according to body weight 1

Pregnant Women:

• Malaria infection in pregnant women may be more severe with increased risk of adverse pregnancy outcomes 1
• Chloroquine is safe during pregnancy and remains the drug of choice in areas without resistance 1
• Pregnant women should avoid travel to areas with chloroquine-resistant P. falciparum as mefloquine and doxycycline are contraindicated during pregnancy 1
• Proguanil has been widely used for decades with no established adverse effects on pregnancy or fetus 1

Breastfeeding Women:

• Small amounts of antimalarial drugs are secreted in breast milk but are insufficient to provide protection to nursing infants 1
• Infants requiring chemoprophylaxis should receive the recommended dosages of antimalarials directly 1

Drug-Specific Considerations and Side Effects

Mefloquine:

• Not recommended for travelers with hypersensitivity to mefloquine, history of epilepsy or psychiatric disorder, or those using beta blockers 1
• Neuropsychiatric side effects (anxiety, depression, sleep disturbances, hallucinations) may occur, usually with the first three doses 1
• Women of childbearing potential should use reliable contraception during prophylaxis and for 2 months after the last dose 1

Doxycycline:

• May cause photosensitivity (minimize by avoiding sun exposure, using UVA-absorbing sunscreens, taking the drug in evening) 1
• Can increase frequency of monilial vaginitis 1
• Gastrointestinal side effects may be minimized by taking with meals 1

Primaquine:

• May cause severe hemolysis in G6PD-deficient individuals 1
• G6PD deficiency should be ruled out by laboratory testing before use 1
• Contraindicated during pregnancy as it may cause hemolytic anemia in a G6PD-deficient fetus 1

Proguanil:

• Rarely causes adverse reactions at prophylactic dosage 1
• Reported side effects include nausea, vomiting, and mouth ulcers 1

Hydroxychloroquine:

• Similar to chloroquine with rare serious adverse reactions at prophylactic doses 2, 3
• Requires ophthalmologic monitoring for retinopathy with long-term use (>6 years) 2, 3
• Use with caution in patients with G6PD deficiency 4, 3

Emerging Approaches to Antimalarial Therapy

• Artemisinin derivatives show excellent efficacy against P. falciparum with minimal toxicity 5, 6
• Combination therapy (particularly artemisinin-based combinations) is increasingly recommended to reduce the risk of resistance development 7, 8
• Using combinations of antimalarials with different resistance mechanisms significantly reduces the chance of selection for resistant parasites 7, 8

Prevention Beyond Chemoprophylaxis

• Use insect repellents containing DEET on exposed skin (apply sparingly to minimize adverse reactions) 1
• Sleep under mosquito nets impregnated with pyrethroids (e.g., permethrin) 1
• Wear long-sleeved clothing and long trousers if outdoors after sunset 1
• Use electric mats to vaporize synthetic pyrethroids or burn mosquito coils overnight 1