Plaquenil (generic: hydroxychloroquine) is a prescription medication used to reduce pain and swelling caused by diseases of the immune system such as rheumatoid arthritis, juvenile arthritis, and systemic lupus erythematosus (SLE). This medication belongs to a group of drugs called DMARDs (disease modifying antirheumatic drugs) which work by suppressing the excessive activity of the immune system.

Plaquenil is also used to prevent and treat malaria. For this reason, it is sometimes classified as an antimalarial drug. The exact way it works for this condition is unknown.

Plaquenil comes in tablet form. It is taken once or twice a day, unless it is used for the prevention of malaria, in which case it is taken once a week beginning 1 to 2 weeks prior to traveling to an area where malaria is common. Take this medication with a meal or a glass of milk to prevent stomach upset.

Common side effects include nausea, loss of appetite, headache, and diarrhea. Plaquenil can cause blurred vision and dizziness. Do not drive or operate heavy machinery until you know how it affects you.