1 What is this medicine
and what is it used for?
Primaquine is an 8-aminoquinoline antimalarial active
specifically against the dormant liver stage (hypnozoites) of Plasmodium vivax
and P. ovale malaria parasites — the only stage that can cause malaria relapses
weeks to months after the initial infection. It is the cornerstone drug for
radical cure (elimination of the hypnozoite reservoir) and relapse prevention
of P. vivax and P. ovale malaria.
It is used for:
• Radical cure (prevention of relapse)
of P. vivax and P. ovale malaria — 15 mg/day for 14 days (standard regimen) or
30 mg/day for 14 days in high-risk vivax regions.
• Causal prophylaxis of malaria in
travellers to P. vivax endemic areas — daily dosing.
• Gametocidal therapy in P. falciparum
malaria — a single dose (15–45 mg) to clear circulating gametocytes and reduce
transmission.
2 How to take this
medicine
Take once daily with food to reduce GI upset. Swallow whole
with water. A standard 14-day course requires 14 tablets. The 140-tablet pack
supports an extended prevention course. Take at the same time each day.
|
CRITICAL — G6PD TESTING BEFORE USE: Primaquine can cause severe haemolytic anaemia
(destruction of red blood cells) in patients with G6PD (glucose-6-phosphate
dehydrogenase) deficiency — a common inherited enzyme deficiency (affects up
to 10–20% of populations in malaria-endemic regions). ALL patients must have G6PD status confirmed
BEFORE starting primaquine — by either laboratory G6PD enzyme assay or
validated rapid diagnostic test. G6PD-deficient patients must NOT receive
standard daily primaquine — alternative regimens (weekly primaquine,
tafenoquine with specialist supervision) or alternative drugs should be
considered. Symptoms of haemolysis: dark urine
(brown/black), jaundice, pallor, rapid heart rate, severe fatigue — seek
medical attention immediately. |
3 Possible side effects
|
Frequency |
Side Effect |
What to Do |
|
Very Common (in G6PD
deficiency) |
Haemolytic anaemia |
STOP immediately; seek
urgent medical care. Transfusion may be required. |
|
Very Common (>10%) |
Nausea / abdominal
cramps |
Take with food.
Usually mild. |
|
Common (1–10%) |
Methemoglobinaemia
(especially at high doses) |
Symptoms: cyanosis
(bluish discolouration), headache, dizziness. Seek urgent review. |
|
Common (1–10%) |
Abdominal pain |
Usually mild; take
with food. |
|
Uncommon |
Agranulocytosis (very
rare) |
Report any infection,
fever, or mouth ulcers. |
4 Contraindications
Primaquine is contraindicated in: G6PD deficiency (standard
regimen — severe haemolysis risk); pregnancy (neonatal G6PD status unknown —
haemolysis risk in foetus); breastfeeding if infant's G6PD status unknown; and
concomitant use with other drugs causing haemolysis or methemoglobinaemia.
5 Drug interactions
• Quinacrine: potentiates primaquine
toxicity — do not combine.
• Drugs associated with haemolysis or
methemoglobinaemia (dapsone, sulfonamides, nitrofurantoin, certain
antimalarials): additive haematological toxicity.
• CYP2D6 inhibitors (fluoxetine,
paroxetine, quinidine): primaquine is metabolised by CYP2D6; inhibitors may
reduce conversion to active carboxyprimaquine and alter efficacy.
6 Storage
Store below 25°C, away from direct light. Original blister
pack. Keep out of reach of children.
7 Prescription
requirement
|
PRESCRIPTION ONLY MEDICINE (POM) — Prescribed
by a physician experienced in tropical medicine/infectious diseases. G6PD testing is mandatory before dispensing in
all patients. Document G6PD result in patient records before supplying. |
8 Guidance for patients
& caregivers
Primaquine is essential to prevent malaria relapsing weeks or
months after you return home from an endemic area. P. vivax malaria has dormant
parasites hiding in the liver that only primaquine can eliminate. Without this
14-day course, relapses can occur repeatedly.
Take every tablet with food and complete the full course.
Watch for dark (brown or black) urine, yellowing of skin or eyes, or unusual
pallor — these could be signs of haemolysis (blood cell breakdown) and require
urgent medical attention.
9 Pharmacist &
prescriber notes
The 140-tablet pack at 15 mg covers: 14-day standard course
(14 tablets) — 10 courses; or extended prophylaxis courses. In practice, a
14-day course for radical cure should be supplied as 14 tablets from this pack.
G6PD testing: quantitative spectrophotometric assay is gold
standard; qualitative rapid tests are acceptable in resource-limited settings.
For G6PD intermediate-activity patients: WHO recommends supervised weekly
primaquine 45 mg for 8 weeks as an alternative (reduces haemolysis risk).
Tafenoquine (a long-acting 8-aminoquinoline) is now available as a single-dose
alternative for radical cure in G6PD-normal patients — discuss with tropical
medicine specialist.
10 Frequently asked
questions
I completed my malaria treatment — why do I need this
course too?
Standard malaria treatment (e.g. chloroquine) kills the
blood-stage parasites that cause symptoms but does not eliminate the
liver-stage (dormant) parasites. Primaquine is the only medicine that
eliminates the liver stage.
What does dark or black urine mean?
If your urine turns dark brown or black, this could mean your
red blood cells are being destroyed (haemolysis). Stop primaquine immediately
and seek urgent medical attention. This is a sign of a potentially serious
reaction.
Can I take primaquine if I am pregnant?
No — primaquine is not safe in pregnancy because the baby's
G6PD status is unknown and haemolysis could harm the foetus. Malaria relapses
during pregnancy are managed with suppressive therapy (e.g. chloroquine weekly)
until the baby is born and G6PD tested.
Will I get sick if I have G6PD deficiency?
Standard daily primaquine (15 mg/day) can cause serious
haemolytic anaemia in G6PD-deficient patients. Alternative approaches — such as
weekly supervised primaquine — may be used in some cases. This decision must be
made by a tropical medicine specialist.