Hydroxychloroquine is classified as an anti-malarial drug. It is similar to chloroquine (Aralen) and is useful in treating several forms of malaria as well as lupus erythematosus and rheumatoid arthritis. Its mechanism of action is unknown. Malarial parasites invade human red blood cells. Hydroxychloroquine may prevent malarial parasites from breaking down (metabolizing) hemoglobin in human red blood cells. Hydroxychloroquine is effective against the malarial parasites Plasmodium vivax, P. malariae, P. ovale, and susceptible strains of P. falciparum. Hydroxychloroquine prevents inflammation caused by lupus erythematosus and rheumatoid arthritis. The FDA approved hydroxychloroquine in April, 1955.

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Side effects include irritability, headache, weakness, hair lightening or loss, stomach upset, nausea, dizziness, muscle pain, rash and itching. Rarely, hydroxychloroquine can affect the bone marrow leading to reduced white blood cells (leukopenia) or platelets (thrombocytopenia) and abnormal red blood cells (anemia). Rare but potentially serious eye toxicity can occur. This toxicity affects a part of the eye called the retina and can lead to color blindness and even loss of vision. An ophthalmologist (eye specialist) often can detect changes in the retina that suggest toxicity before serious damage occurs. Therefore, regular eye examinations, even when there are no symptoms, are mandatory. Patients who are genetically deficient in a certain enzyme, called G6PD, can develop a severe anemia resulting from the rupture of red blood cells. This enzyme deficiency is more common in persons of African descent and can be evaluated by blood testing. Hydroxychloroquine may worsen psoriasis.

The usual adult dose for treating malaria is 800 mg initially, followed by 400 mg 6-8 hours later and then 400 mg at 24 hours and 48 hours. The dose for malaria prevention is 400 mg every week starting 1 or 2 weeks before exposure and for 4 weeks after leaving the high risk area.

The recommended adult dose for rheumatoid arthritis is 400-600 mg daily for 4-12 weeks followed by 200-400 mg daily.

Systemic lupus erythematosus is treated with 400 mg once or twice daily for several weeks then 200-400 mg daily. Hydroxychloroquine should be taken with food or milk in order to reduce stomach upset.

Administration of hydroxychloroquine with penicillamine (Cuprimine, Depen) may increase penicillamine levels, increasing the risk of penicillamine side effects. The mechanism is unknown. Combining telbivudine (Tyzeka) and hydroxychloroquine may increase the risk of unexplained muscle pain, tenderness, or weakness because both drugs cause such side effects.

Hydroxychloroquine suppresses the immune system and should not be combined with drugs that also suppress the immune system or live vaccines.

Hydroxychloroquine should only be used in pregnant women for malaria prophylaxis or treatment.

Hydroxychloroquine may be secreted in breast milk and may cause side effects in the infant.

What preparations of hydroxychloroquine are available?

Tablet: 200 mg.

How should I keep hydroxychloroquine stored?

Hydroxychloroquine should be stored at room temperature up to 30 C (86 F) in a sealed, light resistant container.