Plaquenil (generic name: hydroxychloroquine) is a medicine that doctors often prescribe for rheumatoid arthritis, systemic lupus erythematosus and a number of other rheumatic and inflammatory conditions. It is considered an "antimalarial" drug. That’s because it belongs to a class of antibiotics that help treat malaria.

Hydroxychloroquine is considered one of the safest arthritis drugs available. 

In addition to its use as a treatment, recent studies suggest that it may also help prevent certain conditions or complications. For example, it may be associated with a lower risk of developing diabetes. And it may help prevent lupus from becoming a more severe disease. Many lupus experts now recommend their patients take hydroxychloroquine even if their disease is quiet.

Most people taking hydroxychloroquine have no side effects. But as with any medicine, allergic reactions sometimes happen. These include hives, other rashes or, rarely, more severe allergic reactions.

More common side effects include nausea, loss of appetite or diarrhea. In rare cases, patients get fever, blurred vision, nightmares, or muscle weakness.  

The most concerning side effect is damage to the retina at the back of the eye. This critical part of the eye receives visual information and sends it to the brain. For this reason, people taking hydroxychloroquine long term should have regular eye exams by an eye specialist. This is especially important if you take it for more than 5 years or if you are less than 135 pounds. 

Fortunately, when you take hydroxychloroquine in recommended doses and you’re properly monitored, damage to the eye is very rare.