Everything about Primaquine totally explained
Primaquine (or
primaquine phosphate) is a medication used in the treatment of
malaria and
Pneumocystis pneumonia. It is a member of the
8-aminoquinoline group of drugs that includes
tafenoquine and
pamaquine.
Indications
Radical cure
Primaquine is mainly used to treat the
P. vivax or
P. ovale malaria. Once the parasite has been eliminated from the bloodstream, the remaining
hypnozoites must be removed from the liver and this is done by administering a 14 day course of primaquine (called
radical cure).
If primaquine isn't administered to patients with proven
P. vivax or
P. ovale infection, there's a very high likelihood relapse within weeks or months (sometimes years).
When attempting a radical cure, primaquine requires the presence of
quinine or
chloroquine in order to work. If primaquine is given alone, the cure rate is only 21%. This is why primaquine should always be given with quinine or chloroquine. It isn't known if other antimalarials such as
mefloquine are likewise able to potentiate the effect of primaquine.
Primary prophylaxis
Primaquine isn't routinely used to prevent malaria in travellers, and is only used as such when no other alternatives are appropriate. It isn't licensed for this use in the U.S. or UK.
Terminal prophylaxis
Primaquine is also sometimes used presumptively to prevent malaria in people who have gone to areas where
P. vivax or
P. ovale are endemic (called
terminal prophylaxis), but this practise isn't common outside of the U.S. and is controversial.
Pneumocystis pneumonia
Primaquine is also used in the treatment of
Pneumocystis pneumonia, a
fungal infection commonly occurring in people with
AIDS and, more rarely, in those taking
immunosuppressive drugs. To treat PCP effectively it's usually combined with
clindamycin.
Adverse reactions
Side effects of primaquine administration include
nausea, vomiting, and
stomach cramps. Other known adverse effects that occasionally occur are
headache, visual disturbances and intense
itching.
Primaquine has also been shown to cause
Hemolytic anemia in people of African or Mediterranean descent; this was a a plot point in an episode of
M*A*S*H, in which
Max Klinger developed anemia while taking primaquine, confusing the doctors who thought it was only a possibility if he were of African descent.
Primaquine causes
methemoglobinemia in all patients who take it (levels of up to 18% are reported, normal level is <1%), but this seldom causes symptoms and is always self-limiting. Dangerous levels of methemoglobinemia only occur in patients with
glucose-6-phosphate dehydrogenase deficiency.
Contraindications
Primaquine shouldn't be administered to anyone with
Glucose-6-phosphate dehydrogenase deficiency as there can be a severe reaction with
hemolytic anemia. Primaquine is contraindicated in pregnancy, because the
G-6-PD status of the fetus won't be unknown. Primaquine shouldn't be given to patients with
NADH methemoglobin reductase deficiency. (note that older authorities quote 15 mg instead);
Plasmodium ovale: 15 mg once daily for 14 days.
The FDA licensed dose in the U.S. is 15 mg once daily, but this isn't the dose recommended by the CDC for P. vivax; the FDA decision in 1952 to limit the primaquine dose to 15 mg was motivated by the fact that G-6-PD testing wasn't routinely available, 15 mg was known to be effective against the P. vivax strains found in Korea (in the US, the main use of primaquine at that time was to treat soldiers returning from war), and because 15 mg of primaquine isn't likely to cause hemolysis in G-6-PD deficient patients.Primary prophylaxis
The dose of primaquine in primary malaria prophylaxis is 30 mg once daily, starting the day before travel and continuing for 7 days after returning. It needs only to be given for seven days after returning because primaquine is active against liver schizonts (the exoerythrocytic stages) and is therefore a causal prophylactic. In children, the dose is 0.6 mg/kg/day (the maximum daily dose is 30 mg).
Manufacturing and availability
Primaquine was first tested on humans during the Stateville Penitentiary Malaria Study in 1944. Primaquine was licensed for use in the US by the FDA in 1952 and is available as a generic drug from a variety of manufacturers.
Primaquine isn't licensed for use in the UK. It is available on a named patient basis only from Durbin or IDIS. Primaquine tablets available in the UK contain 7.5 mg primaquine base (13.2 mg phosphate salt). Primaquine tablets available in the U.S. contain 15 mg base (26.3 mg phosphate salt).
Further Information
Get more info on 'Primaquine'.
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