Hydroxychloroquine

Hydroxychloroquine is an antimalarial medication used to prevent and treat malaria in areas without chloroquine resistance. It is marketed under the brand name Quensyl® and as a generic.

In addition, hydroxychloroquine is an important medication for autoimmune diseases such as systemic lupus erythematosus (SLE) and rheumatoid arthritis. For malaria prophylaxis, it is only suitable in regions with chloroquine-sensitive plasmodia (parts of Central America, the Near East, parts of Asia).

Mechanism of action (malaria):

• Accumulates in the acidic food vacuole of the malaria parasite
• Inhibits the parasite's heme polymerase
• Toxic heme accumulates and kills the parasite
• Acts against the blood stages (erythrocytic schizonts)

Additional properties:

• Immunomodulatory (hence its use in autoimmune diseases)
• Anti-inflammatory
• Antiproliferative

Limitation: Hydroxychloroquine does not act against liver schizonts. It therefore has to be taken for 4 weeks after the trip to catch parasites that pass from the liver into the blood.

Hydroxychloroquine for malaria prophylaxis is suitable for:

• Travelers to areas WITH chloroquine-sensitive malaria
• Parts of Central America, the Middle East, parts of South Asia
• Long-term travelers (good for longer stays)

Not suitable:

• Areas with chloroquine resistance (sub-Saharan Africa, Southeast Asia, South America)
• Severe retinal diseases (retinopathy)
• Hypersensitivity to 4-aminoquinolines
• G6PD deficiency (risk of hemolysis)
• Myasthenia gravis

Malaria prophylaxis:

• 400 mg (2 tablets of 200 mg each) once weekly
• Start: 1–2 weeks before entering the country
• Throughout the entire stay: weekly
• After leaving the country: another 4 weeks

Available strengths:

• 200 mg film-coated tablets

Day of intake:

• Always take on the same day of the week
• Example: always on Mondays

Intake:

• Once weekly on the same day of the week
• Take with a meal
• With enough water

Prophylaxis schedule: 1. Start: 1–2 weeks before the trip 2. Weekly during the trip 3. Continue taking for 4 weeks after your return

Important notes:

• Take a missed dose as soon as possible
• Use sun protection (phototoxicity possible)
• Mosquito protection remains essential
• Regular eye examinations with long-term use

Hydroxychloroquine must not be taken in case of:

• Pre-existing maculopathy/retinopathy
• Hypersensitivity to hydroxychloroquine or chloroquine
• G6PD deficiency
• Myasthenia gravis

Caution with:

• Epilepsy (lowering of the seizure threshold)
• Liver function disorders
• Renal insufficiency
• Porphyria
• Psoriasis (worsening possible)
• QT prolongation or medications that prolong the QT interval
• Pregnancy (benefit-risk assessment; can be used for malaria prophylaxis)

Common (1–10%):

• Gastrointestinal complaints (nausea, abdominal pain, diarrhea)
• Headache
• Skin rash

Uncommon (0.1–1%):

• Visual disturbances
• Dizziness
• Nervousness, sleep disorders
• Hair loss
• Itching

Rare but serious (long-term use):

• Retinopathy (irreversible retinal damage) – regular eye check-ups!
• Cardiomyopathy
• Neuromyopathy
• Blood count changes
• QT prolongation

Note: With short-term malaria prophylaxis (a few weeks), the risk of serious side effects is very low. Retinopathy is mainly a problem with long-term therapy over years.

Do not use at the same time:

• Halofantrine
• MAO inhibitors
• Substances that damage the liver (caution also with alcohol in larger amounts)

Not recommended:

• Medicines that can damage the retina (e.g. tamoxifen)

Caution when taken at the same time as:

• Medicines that prolong the QT interval, e.g. amiodarone, tricyclic antidepressants, antipsychotics, moxifloxacin, azithromycin or fluconazole (increased risk of heart rhythm disorders)
• Other medicines that can lower the seizure threshold, e.g. mefloquine or bupropion (increased risk of seizures)
• Medicines for epilepsy (their effect may be reduced)
• Insulin and other blood sugar-lowering medicines (the lowering of blood sugar may be increased, and a lower dose of these medicines may be needed)
• Digoxin, dabigatran or ciclosporin (higher blood levels of these medicines possible)
• Methotrexate (its effect is increased)
• Cimetidine and substances that inhibit the breakdown of hydroxychloroquine, e.g. clarithromycin, itraconazole, ritonavir, fluoxetine, paroxetine or grapefruit juice (more side effects possible)
• Rifampicin, St John's wort, carbamazepine, phenobarbital or phenytoin (hydroxychloroquine may work less well)

Keep a time gap:

• Magnesium-containing antacids (stomach acid binders) or kaolin: at least two hours apart from hydroxychloroquine

Vaccinations:

• Rabies vaccination: Antibody formation may be reduced. Vaccination into the muscle is recommended.
• No effect on routine vaccinations (tetanus, diphtheria, measles, poliomyelitis, typhoid and tuberculosis) has been observed.

This list is not complete. Tell your doctor about all medicines you are taking.