10 Questions
What is the purpose of chemoprophylaxis in travelers visiting malaria-endemic areas?
To prevent malaria infections
Why is chloroquine use restricted in many areas?
Due to the development of high rates of chloroquine resistance
What is the mechanism of action of chloroquine against malaria parasites?
Increasing oxidative damage to the parasite
What type of malaria parasites is chloroquine ineffective against?
Liver stage parasites
What is the reason for the toxicity of free heme to malaria parasites?
It causes oxidative damage
What is the primary mediator of chloroquine resistance in Plasmodium falciparum?
Mutations in PfCRT
What is the effect of verapamil on the heart?
It reduces the ionotropic, chronotropic, and dromotropic effects of the heart
What is the primary mechanism of chloroquine resistance reversal by certain agents?
Reversal of chloroquine efflux
What is the characteristic of chloroquine's distribution in the body?
It is rapidly distributed to the tissues and can cross the BBB and placenta
What is the limitation of using chloroquine for malaria treatment?
It does not eliminate hypnozoites of P. vivax and ovale
Study Notes
Chemoprophylaxis for Malaria
- Travelers visiting countries with common malaria are strongly encouraged to undergo chemoprophylaxis using five drugs: chloroquine, malarone, mefloquine, doxycycline, and primaquine.
- These drugs are used depending on the type of malaria and the area of travel.
Chloroquine
- Chloroquine is the oldest antimalarial drug and is commonly used but also misused, leading to high rates of resistance in most countries affected by malaria.
- It is still an effective drug but its use is restricted to areas without resistance.
- Chloroquine is a highly effective blood schizonticide, but it has no effect against other forms of malaria, such as liver stage parasites.
- The mechanism of action involves inhibiting the metabolism of heme groups, which are toxic to malarial parasites.
- Resistance to chloroquine is common among strains of P.falciparum and is increasing for P.vivax.
Resistance to Chloroquine
- Mutations in the PfCRT (P.falciparum chloroquine resistance transporter) are the primary mediators of resistance.
- Chloroquine resistance can be reversed by certain agents, including verapamil, desipramine, and chlorpheniramine.
Pharmacokinetics of Chloroquine
- Chloroquine is rapidly absorbed after oral administration, reaching Tmax in about 3 hours.
- It is rapidly distributed to tissues, including crossing the blood-brain barrier and placenta.
- It concentrates heavily in the spleen, kidneys, lungs, and leukocytes.
- It is excreted into the urine and has an early half-life of 3-5 days and an elimination half-life of 1-2 months.
- It exhibits a very long terminal elimination half-life.
Indications and Clinical Applications of Chloroquine
- Chloroquine is the drug of choice in areas without parasitic resistance and for uncomplicated non-falciparum and sensitive falciparum malaria.
- It is a wide-spectrum drug for parasites but clinical resistance is very high.
- It does not eliminate hypnozoites of P.vivax and ovale, so primaquine must be added to completely eradicate these hypnozoites.
- Chloroquine is safe to use in pregnancy.
This quiz covers the different drugs used for the treatment and prevention of malaria, including chloroquine, malarone, mefloquine, doxycycline, and primaquine.
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