Primaquine is prescribed to prevent relapses of malaria caused by Plasmodium vivax. It also helps to prevent the spread of falciparum malaria. It is not used alone but in combination with other antimalarial drug/drugs for these purposes. It may also be used to prevent malaria in travelers.
Primaquine is also used in combination with clindamycin for treating pneumocystis pneumonia (a fungal infection in lungs commonly seen in AIDS patients and patients taking immunity-suppressing drugs).
Primaquine should not be taken in the following conditions:
• Glucose-6-phosphate dehydrogenase (G6PD) enzyme deficiency. Lack of the enzyme leads to red blood cell destruction on administration of drugs like primaquine
• Autoimmune diseases (in which the body immune system mistakenly produces antibodies and attacks its tissues) such as rheumatoid arthritis and lupus erythematosus, since there is a tendency for granulocytopenia (reduced number of granulocytes-a type of white blood cells)
• Hemolytic anemia or patients taking hemolytic drugs (that cause destruction of red blood cell)
Methemoglobinemia (higher blood levels of methemoglobin, an atypical form of hemoglobin)
• Bone marrow depression and leukopenia as it has toxic effects on the blood
• Pregnant women and infants
• Patients who are taking or have recently taken quinacrine, since quinacrine increases the toxicity of primaquine
The dosage of the drug is usually calculated as a base. Each 26.3mg tablet of primaquine phosphate is equivalent to 15mg primaquine base. The dosage may vary according to local or regional recommendations.
a) For preventing relapses of malaria:
Adult dose: The recommended dose is 15mg base once daily for 14 days
b) For preventing spread of falciparum malaria:
45 mg single dose on the second day of treatment (Ref: Guidelines for Diagnosis and Treatment of Malaria in India 2014; National Institute of Malaria Research / National Vector Borne Disease Control Program, New Delhi)
c) For treating Pneumocystis jiroveci pneumonia:
The recommended dose in treating AIDS (HIV infected) patients is 30mg orally once daily for 21 days in combination with clindamycin.
d) Travellers to malaria-infected areas:
Persons should start taking primaquine before 2 days, during the stay and for 7 days after leaving the infected area. Travelers who were continuously exposed to P. vivax or P.ovale should take it for 14 days after leaving the place along with another antimalarial drug (Ref: CDC). The recommendations however vary depending on the country being visited.
• Primaquine comes as a tablet and to be taken by mouth.
• It should be taken at the same time every day.
• Skipping the doses or stop taking the tablets may not completely cure the infection and may come back.
• Large doses of primaquine must be avoided as leukopenia (a decrease in the number of white blood cells) can occur.
• Primaquine treatment should be discontinued immediately when leukopenia occurs.
• Patients should avoid pregnancy during primaquine treatment.
• Sexually active women should take effective contraceptive pills and men should use a condom during and 3 months after stopping the treatment.
• Gastrointestinal:Pain in the stomach, heartburn, nausea and vomiting
• Eye: Blurred vision
• Cardiovascular system: Fast, slow or irregular heartbeat (prolonged QT interval may be noted on ECG)
• Blood: Reduced white blood counts. Hemolysis may occur especially in patients with G6PD enzyme deficiency. The patient may present with yellow discoloration of eyes, dark colored urine, pale lips or skin, shortness of breath, and dizziness. Methemoglobinemia may also occur with symptoms of grayish discoloration of the skin and lips, headache, fatigue and chestpain
• Allergic reaction: Rashes, itching
• Blood cell counts and hemoglobin levels should be monitored regularly as anemia, leucopenia, and methemoglobinemia could occur during the therapy.
• Since G6PD test assay is widely not available, due to the risk of hemolysis (rupturing of red blood cell), adequate medical support and follow-up should always be available.
• ECG monitoring is required particularly in patients with heart illness as primaquine can result in abnormal heart rhythm.
Several drugs interact with primaquine. Some of the interactions include:
• Chances of bleeding may increase with drugs that can cause hemolysis including cephalosporin, nitrofurantoin, levofloxacin, penicillin, levodopa, methyldopa, and NSAIDs
• Quinacrine increases the toxicity of primaquine
• Prolonged QT interval (heart rhythm problem) could occur when given with other drugs like quinidine, thioridazine or amiodarone administered with primaquine.
• Store at a room temperature in the tight container.
• It should be protected from light.
• Keep away from excess heat and moisture.
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