Anti-Malarial Medications for Chemoprophylaxis
MALARIA
Anti-Malarial Medications for Chemoprophylaxis:
Control of malaria has become increasingly complex and controversial. Once suppressed by chloroquine alone, resistant strains of malaria have now developed in many areas. It may now be necessary to use a variety of medications to provide optimal protection depending on the areas being travelled. Travellers may encounter various recommendations reflecting the differences of opinion in this area.
Prophylaxis: Anti-malarial medication should be taken prior to arrival and throughout the stay in a malaria area. The medication is continued for a set time after departure from the malaria area.
The most widely used drugs to prevent malaria (i.e. mefloquine, chloroquine and doxycycline) suppress signs and symptoms of the disease by eliminating the parasites once they’ve left the liver, during the multiplication phase in the red blood cells. They work best against P. falciparum and P. malariae, as these parasites have a shorter liver phase, resulting in appearance in the bloodstream when the drugs are present. Disease in the blood from P. vivax and P. ovale cannot always be prevented when prophylaxis ends after four weeks, as they can lie dormant in the liver for a long time, with signs and symptoms not developing for months or even years.
Drugs like atovaquone/proguanil (Malarone®) and primaquine, however, eliminate the parasites in the liver as well as the blood, thus requiring a shorter period of use (7 days) following exposure. It is important to recommend a drug that will provide protection against the P. falciparum parasite, which causes the most serious and often fatal form of malaria.
Malaria Chemoprophylaxis Regimens for At-Risk Individualsa According to Presence of Drug Resistance Region Drug(s) of Choiceb Alternatives Chloroquine sensitive Chloroquine or hydroxychloroquine d Atovaquone/proguanil˓, doxycycline , mefloquine (Plaquenil®) e Chloroquine resistant d Primaquine Atovaquone/proguanil˓, doxycycline , or mefloquine Chloroquine and Mefloquine Doxycyclined or resistant atovaquone/proguanil˓ a. IMPORTANT: Protection from mosquito bites (bed nets, insect repellents, etc) is the first line of defense against malaria for ALL travellers b. See CATMAT Malaria Statement, Table 8.11 for adult and pediatric dosing information • In Canada, atovaquone/proguanil is currently licensed for prophylactic use in individuals greater than 11 kg. The Committee to Advise on Tropical Medicine and Travel (CATMAT) recommends the use in children less than 11kg • Although the manufacturer recommends that mefloquine not be given to children smaller than 5 kg (11 lb), according to CATMAT, mefloquine should be considered for all children at high risk of acquiring chloroquine-resistant P. falciparum, at a dose of 5 mg base/kg once weekly c. Contraindicated in pregnancy and insufficient data exist for use in children less than 5 kg d. Contraindicated in pregnancy, during breastfeeding and in children less than 8 years of age e. Contraindicated in G6PD (glucose-6-phosphate dehydrogenase) deficiency and in pregnancy June 26, 2020
ADDITIONAL NOTES:
Proguanil: • CATMAT does not recommend its use as a single agent for prophylaxis
Oral Anticoagulant Therapy and Malaria Chemoprophylaxis: • Refer to the specific section for further information
Malaria Prescription Referral Form (Section VI, Fact Sheets): • Use when referring a client to a prescriber for a prescription for malaria medication
Switching Antimalarial Medications: • This practice is not optimal since it can be complicated and if mistakes are made, they can in some cases, be life threatening • In most cases, it is recommended that the traveller remain on one antimalarial throughout the whole time needed for their trip • Prescribers, as well as the traveller, need to understand the principles and mechanics of switching between antimalarials; at times, changing from one antimalarial to another may be warranted in certain situations: o Not tolerating a medication o Lengthy trip (ex; in chloroquine sensitive area for long term stay then going to chloroquine resistant area long term) • Refer to Table 4-12 in the CDC Yellow Book, for guidelines on Changing Medications as a Result of Side Effects during Malaria Chemoprophylaxis
Doxycycline Use in Clients already taking Minocycline for a Pre-existing Condition: o Insufficient data exist on the antimalarial prophylaxis efficacy of minocycline, as noted by CDC and CATMAT o Travellers taking minocycline for the treatment of acne or rheumatoid arthritis and for whom doxycycline was recommended for malaria chemoprophylaxis should switch to doxycycline 100 mg daily the day before arrival in the malaria-endemic area. Once they have completed their anti-malarial chemoprophylaxis (including the 4 weeks of doxycycline chemoprophylaxis after leaving the malaria-endemic area), they should resume their former dose of minocycline. o Travellers should use an effective sunscreen, especially since the dose of doxycycline used for malaria chemoprophylaxis may be higher than the minocycline dose used in the treatment of acne. o Carefully document the plan for malaria chemoprophylaxis o Sources: . CATMAT Statement on Canadian Recommendations for the Prevention and Treatment of Malaria, 2019 (Chapter 8) . CDC Health Information for International Travel, Yellow Book, 2020 (page 280)
June 26, 2020 Malaria Life Cycle and Primary Areas of Drug Activity:
Source: CATMAT Statement on Canadian Recommendations for the Prevention and Treatment of Malaria, 2019 (Chapter 8)
June 26, 2020