Chloroquine for Malaria Prophylaxis
Chloroquine remains effective for malaria prophylaxis only in geographic areas without chloroquine resistance, but is no longer appropriate for most malarious regions due to widespread resistance in P. falciparum and emerging resistance in P. vivax. 1
Geographic Limitations and Resistance Patterns
Chloroquine resistance is now widespread in P. falciparum globally and has been documented in P. vivax, particularly in Papua New Guinea, Indonesia (Irian Jaya), and parts of South Asia. 1
The FDA label explicitly states that chloroquine should not be used for malaria prophylaxis in areas where chloroquine resistance occurs, and travelers must verify regional appropriateness before use. 1
In sub-Saharan Africa, where 80% of U.S. civilian malaria cases were acquired during 1980-1988, chloroquine-resistant P. falciparum is common, making alternative agents necessary. 2
Research from Irian Jaya demonstrated that 70% of children under 4 years failed chloroquine treatment despite adequate blood concentrations, and 9 of 17 subjects on weekly prophylaxis developed parasitemia within 8 weeks. 3
Recommended Alternatives in Resistant Areas
For areas with high chloroquine resistance (particularly sub-Saharan Africa), mefloquine 250 mg weekly is the CDC's first-line alternative for prophylaxis. 4
Doxycycline serves as an alternative for short-term travelers or in mefloquine-resistant areas of East Asia. 2, 4
Atovaquone-proguanil is recommended by the CDC for areas with chloroquine resistance. 4
For travelers unable to take mefloquine, options include doxycycline alone or chloroquine with standby Fansidar treatment available while seeking medical evaluation for febrile illness. 2
Proper Use When Chloroquine Is Appropriate
When chloroquine is used in non-resistant areas, the standard dose is 300 mg base weekly, starting 1-2 weeks before travel and continuing for 4 weeks after leaving the endemic area. 2, 4
Hydroxychloroquine is interchangeable with chloroquine for prophylaxis in non-resistant areas, with both drugs rarely causing serious adverse reactions at prophylactic doses. 4
The CDC emphasizes that most malaria deaths occur in travelers who do not fully comply with prophylaxis regimens, making adherence critical. 4
Critical Limitations
Chloroquine does not prevent relapses from P. vivax or P. ovale because it does not treat the hypnozoite liver stage forms. 1
Additional treatment with primaquine (15 mg base daily for 14 days) is required for terminal prophylaxis after G6PD testing, particularly for persons with prolonged exposure. 4, 5
Chloroquine is not effective against complicated malaria (high-grade parasitemia, cerebral malaria, or acute renal failure). 1
Safety Monitoring
Periodic ophthalmologic examinations are recommended for persons using chloroquine for extended periods (>6 years cumulative weekly prophylaxis). 4
Chloroquine should be used with caution in patients with cardiac disease, as it can cause QT prolongation, ventricular arrhythmias, and cardiomyopathy. 1
The drug may exacerbate psoriasis and cause severe hypoglycemia, including loss of consciousness. 4, 1
Common Pitfalls
No prophylactic regimen guarantees complete protection—travelers must also use insect repellents, wear protective clothing, and seek immediate medical evaluation if fever develops during or after travel. 4
Chloroquine prophylaxis can change clinical manifestations and delay correct diagnosis, creating a false sense of security. 6
In areas where P. vivax predominates with low P. falciparum risk, standby treatment may be more appropriate than continuous prophylaxis to minimize drug overuse and adverse effects. 6