How does this medication work? What will it do for me?

Primaquine belongs to the class of medications called antimalarials. It is used to cure malaria caused by Plasmodium vivax and Plasmodium ovale by killing the parasite when it is in the bloodstream.

Certain types of mosquitoes in tropical climates carry the parasites that cause malaria. Humans develop malaria after they are bitten by a mosquito carrying the parasites. These parasites, Plasmodia, invade the red blood cells, multiply, and cause the red blood cells to burst. This releases more parasites into the blood and causes the symptoms associated with malaria infection.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

What form(s) does this medication come in?

Each pink, film-coated, convex, round tablet, imprinted in black ink with a stylized "W" and "P97" on one side and plain on the other side, contains primaquine phosphate USP 26.3 mg (equivalent to primaquine base 15 mg). Nonmedicinal ingredients: cellulose (microcrystalline), hydroxypropylmethylcellulose, lactose, magnesium stearate polyethylene glycol 400, polysorbate 80, red iron oxide, starch, talc, and titanium dioxide.

How should I use this medication?

The recommended adult dose of primaquine to cure vivax and ovale malaria is 15 mg (one tablet), taken by mouth, once daily for 14 days.

The dose for children is based on the child's body weight and is usually given as 0.39 mg primaquine base per kilogram of body weight. This dose is given once daily for 14 days. Your doctor will calculate the appropriate dose for your child.

Primaquine may be taken with food or on an empty stomach, but taking it after a meal may help to reduce side effects such as abdominal pain or cramping.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.

Do not dispose of medications in wastewater (e.g. down the sink or in the toilet) or in household garbage. Ask your pharmacist how to dispose of medications that are no longer needed or have expired.

Who should NOT take this medication?

Do not take this medication if you:

  • are allergic to primaquine or any ingredients of the medication
  • are experiencing a flare-up of rheumatoid arthritis or lupus erythematosus
  • are receiving other medications that cause breakdown of blood cells or reduced blood cell production
  • have recently been treated with the medication quinacrine

What side effects are possible with this medication?

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

  • abdominal cramps or pain
  • nausea
  • vomiting

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

  • signs of anemia (low red blood cells; e.g., dizziness,  pale skin, unusual tiredness or weakness, shortness of breath)
  • signs of abnormal heart rhythms (e.g., fast or slow heart rate, palpitations, fainting or seizures)
  • signs of infection (symptoms may include fever or chills, severe diarrhea, shortness of breath, prolonged dizziness, headache, stiff neck, weight loss, or listlessness)
  • signs of liver problems (e.g., nausea, vomiting, diarrhea, loss of appetite, weight loss, yellowing of the skin or whites of the eyes, dark urine, pale stools)
  • signs of red blood cells being destroyed (e.g., dark urine, fatigue, shortness of breath, lightheadedness, pale skin)

Stop taking the medication and seek immediate medical attention <if any of the following occur:

  • signs of methemoglobinemia (e.g., grey-blue shade to skin, lips, fingernails; headache, shortness of breath, fainting, irregular heart beat)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Are there any other precautions or warnings for this medication?

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Anemia: Primaquine may cause low levels of red blood cells. If you experience symptoms of reduced red blood cell count (anemia) such as shortness of breath, feeling unusually tired, or pale skin, contact your doctor as soon as possible.

Your doctor will do blood tests regularly to monitor the number of specific types of blood cells, including red blood cells, in your blood.

Heart rhythm: Primaquine can cause changes to the normal rhythm of the heart, including an irregular heartbeat called QT prolongation. QT prolongation is a serious life-threatening condition that can cause fainting, seizures, and sudden death. If you are at risk for heart rhythm problems (e.g., people with heart failure, angina, low potassium or magnesium levels), discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Infection: Primaquine can reduce the number of cells that fight infection in the body (white blood cells). Tell your doctor as soon as possible if you notice signs of an infection, such as fever or chills, severe diarrhea, shortness of breath, prolonged dizziness, headache, stiff neck, weight loss, or listlessness. Your doctor will do blood tests regularly to monitor the number of specific types of blood cells in your blood.

Other medical conditions: If you have a history of hemolytic anemia, glucose-6-phosphate dehydrogenase (G-6_PD) deficiency, nicotinamide adenine dinucleotide (NAD), or methemoglobin reductase deficiency, you may be at higher risk of side effects with primaquine. Inform your doctor if you have been diagnosed with any of these conditions at any point in time.

Pregnancy: This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: It is not known if primaquine passes into breast milk. If you are a breast-feeding mother and are taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

What other drugs could interact with this medication?

There may be an interaction between primaquine and any of the following:

  • abiraterone acetate
  • amiodarone
  • beta-adrenergic blockers (e.g., atenolol, propranolol, sotalol)
  • bexarotene
  • bosentan
  • bromazepam
  • bupropion
  • carbamazepine
  • celecoxib
  • chloroquine
  • chlorpromazine
  • cinacalcet
  • clobazam
  • clomipramine
  • clozapine
  • cyclobenzaprine
  • cyclosporine
  • dabrafenib
  • dacarbazine
  • dapsone
  • darunavir
  • deferasirox
  • desipramine
  • dexamethasone
  • digoxin
  • diphenhydramine
  • dofetilide
  • dronedarone
  • duloxetine
  • estrogens (estradiol, conjugated/equine, esterified, estropipate)
  • enzalutamide
  • fluoxetine
  • flutamide
  • fluvoxamine
  • haloperidol
  • HIV non-nucleoside reverse transcriptase inhibitors (NNRTIs; e.g., delaviridine, efavirenz, etravirine, nevirapine)
  • hydrocodone
  • imatinib
  • isoniazid
  • ketoconazole
  • lidocaine
  • lopinavir
  • medications to treat parasites (i.e., worms; albendazole, mebendazole, praziquantel, pyrantel pamoate)
  • mefloquine
  • melatonin
  • methadone
  • mexiletine
  • mirabegron
  • mirtazapine
  • mitotane
  • modafinil
  • nilotinib
  • olanzapine
  • paroxetine
  • peginterferon Alfa-2b
  • phenobarbital
  • phenytoin
  • pimozide
  • prilocaine
  • primidone
  • quinidine
  • quinine
  • rasagiline
  • rifabutin
  • rifampin
  • ritonavir
  • ropinirole
  • St. John's wort
  • sertraline
  • terbinafine
  • theophyllines (e.g., aminophylline, oxtriphylline, theophylline)
  • ticlopidine
  • tocilizumab
  • tranylcypromine

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

  • stop taking one of the medications,
  • change one of the medications to another,
  • change how you are taking one or both of the medications, or
  • leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.