Chloroquine and Hydroxychloroquine interaction
Chloroquine and Hydroxychloroquine: both prescribing labels flag this combination with the strongest language, such as a contraindication, a boxed warning, or an instruction to avoid it.
Do not combine without a prescriber's guidance. The label language below is the strongest FDA uses.
What the FDA labels say
From the Hydroxychloroquine (Plaquenil) label · effective 2026-04-09
Therefore, PLAQUENIL is not recommended in patients taking other drugs that have the potential to prolong the QT interval.
Cimetidine Concomitant use of cimetidine resulted in a 2-fold increase of exposure of chloroquine, which is structurally related to hydroxychloroquine.
Praziquantel Chloroquine has been reported to reduce the bioavailability of praziquantel.
Antacids and kaolin Antacids and kaolin can reduce absorption of chloroquine; an interval of at least 4 hours between intake of these agents and chloroquine should be observed.
Ampicillin In a study of healthy volunteers, chloroquine significantly reduced the bioavailability of ampicillin.
From the Chloroquine (Chloroquine Phosphate) label · effective 2026-01-13
Patients infected with a resistant strain of plasmodia as shown by the fact that normally adequate doses have failed to prevent or cure clinical malaria or parasitemia should be treated with another form of antimalarial therapy.
WARNINGS Chloroquine-Resistant Malaria Chloroquine phosphate tablets are not effective against chloroquine- or hydroxychloroquine-resistant strains of Plasmodium species (see CLINICAL PHARMACOLOGY , Microbiology ).
Taking more than these two? Interactions stack. Check your whole list at once; it stays in your browser.
Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.