text: what is hydroxychlorq? i would like to know what it is used for and side effects. do you mean hydroxychloroquine? if so, then it's an anti-malarial drug. it's used to treat or to prevent infection from mosquitoes. it's also used as an immune system suppressant for people with autoimmune diseases like lupus or rheumatoid arthritis. side effects: nausea, stomach cramps, loss of appetite, diarrhea, dizziness, or headache may occur. those are the most common. this med can also cause eye and muscle damage.