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 liver.

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.

Primaquine 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 Primaquine 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 Primaquine without consulting your doctor.

Do not give Primaquine 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.

The recommended dose of primaquine for adults varies depending on the person’s weight, the climate where the person had been travelling, and whether they are deficient in the enzyme G6PD. Usual dosages range between 15 mg and 30 mg, taken once daily for 14 days. Your doctor will determine the best dose for you based on your circumstances.

The dose of primaquine for children is based on body weight and whether they are deficient in the enzyme G6PD. Your doctor will calculate the correct 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 Primaquine 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.

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 Primaquine. If you are concerned about side effects, discuss the risks and benefits of Primaquine with your doctor.

The following side effects have been reported by at least 1% of people taking Primaquine. 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
• dizziness
• heartburn
• itching
• nausea
• rash
• 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 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 Primaquine.

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 26.3 mg of primaquine phosphate USP (equivalent to 15 mg of primaquine base). Nonmedicinal ingredients: carnauba wax, cellulose (microcrystalline), lactose, magnesium stearate Opacode Black ink S-1-177003 (contains shellac glaze, propylene glycol, N-butyl alcohol, black iron oxide, ethanol and methanol), Opadry white YS-1-7443 (contains hypromellose, polyethylene glycol 400, titanium dioxide, polysorbate 80), polyethylene glycol 400, red iron oxide, starch, and talc.

Do not take Primaquine if you:

• are allergic to primaquine or any ingredients of the medication
• are experiencing a flare-up of Rheumatoid Arthritis or Lupus erythematosus
• are very sick with a disease or condition that affects blood cell production
• are receiving other medications that cause breakdown of blood cells or reduced blood cell production
• have recently been treated with the medication quinacrine
• are pregnant
• have severe glucose-6 phosphate dehydrogenase (G6PD) deficiency

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

• Abiraterone acetate
• Amiodarone
• Apalutamide
• antipsychotics (e.g., Chlorpromazine,  Fluphenazine, Haloperidol, Olanzapine, Quetiapine, Risperidone, Ziprasidone)
• asunaprevir
• beta-adrenergic blockers (e.g., Atenolol, Propranolol, Sotalol)
• Bosentan
• Bupropion
• Carbamazepine
• chloroquine
• Cinacalcet
• Clobazam
• Cobicistat
• Cyclosporine
• Dapsone
• Darifenacin
• Deferasirox
• Digoxin
• Disopyramide
• Dronedarone
• Duloxetine
• Enzalutamide
• HIV non-nucleoside reverse transcriptase inhibitors (NNRTIs; e.g., efavirenz, etravirine, nevirapine)
• HIV protease inhibitors (e.g., atazanavir, darunavir, ritonavir, tipranavir)
• lidocaine
• macrolide antibiotics (e.g., clarithromycin, erythromycin)
• lumacaftor and Ivacaftor
• Mefloquine
• Methadone
• Mirabegron
• Mitotane
• Modafinil
• pentamidine
• Phenobarbital
• Phenytoin
• prilocaine
• primidone
• procainamide
• Propafenone
• protein kinase inhibitors (e.g., Dabrafenib, Dasatinib, imatinib, Nilotinib, Vandetanib)
• quinidine
• quinine
• quinolone antibiotics (e.g., ciprofloxacin, Norfloxacin, Ofloxacin)
• rifabutin
• rifampin
• St. John's wort
• Sarilumab
• selective serotonin reuptake inhibitors (SSRIs; e.g., Citalopram, Fluoxetine, Paroxetine, Sertraline)
• siltuximab
• sotalol
• terbinafine
• theophyllines (e.g., Aminophylline, Oxtriphylline, Theophylline)
• Tizanidine
• Tocilizumab
• tricyclic antidepressants (e.g., Amitriptyline, Clomipramine, Desipramine, Trimipramine)

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 Primaquine. 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.

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 Primaquine.

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.

Dizziness/reduced alertness: Primaquine may cause dizziness, affecting your ability to drive or operate machinery. Avoid driving, operating machinery, or performing other potentially hazardous tasks until you have determined how you are affected by Primaquine.

Glucose-6-phosphate dehydrogenase enzyme deficiency (G6PD): G6PD deficiency is a hereditary disorder that affects red blood cells. Primaquine can cause destruction of red blood cells for people lacking this enzyme. Before starting Primaquine, your doctor will test to see if you have G6PD deficiency. People without the G6PD enzyme require lower doses of primaquine.

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 Primaquine may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Primaquine, 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.

Liver function: Liver disease or reduced liver function may cause Primaquine to build up in the body, causing side effects. If you have liver problems, discuss with your doctor how Primaquine may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Primaquine, and whether any special monitoring is needed. Your doctor may want to test your liver function regularly with blood tests while you are taking Primaquine.

Other medical conditions: If you have a history of hemolytic anemia, 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: Information about the safety of using Primaquine during pregnancy is limited. It may harm the developing baby if taken by the mother during pregnancy and should not be used during pregnancy. Pregnancy should be avoided during treatment and for 2 menstrual cycles after completing treatment. If you become pregnant while taking Primaquine, contact your doctor immediately. Men taking primaquine should use an effective method of contraception during treatment and for 3 months after the last dose.

Breast-feeding: Primaquine passes into breast milk. If you are a breast-feeding mother and are taking primaquine, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.