IN LUPUS ERYTHEMATOSUS AND RHEUMATOID ARTHRITIS, RESPONSE TO TREATMENT MAY NOT BE APPARENT FOR UP TO 6 MONTHS BUT IF THERE IS NO IMPROVEMENT BY THEN, TREATMENT SHOULD BE STOPPED. IN THE UK, TREATMENT IS USUALLY STARTED WITH 400 MG DAILY IN DIVIDED DOSES WITH MEALS. IN THE USA, RECOMMENDED INITIAL DOSES ARE 400 TO 600 MG DAILY FOR RHEUMATOID ARTHRITIS AND 400 MG ONCE OR TWICE DAILY FOR LUPUS ERYTHEMATOSUS. DOSES ARE REDUCED TO THE MINIMUM EFFECTIVE DOSE FOR MAINTENANCE; THIS IS USUALLY 200 TO 400 MG DAILY BUT SHOULD NOT EXCEED 6.5 MG/KG DAILY (OR 400 MG DAILY WHICHEVER IS THE SMALLER). TO AVOID EXCESSIVE DOSAGE IN OBESE PATIENTS, SPECIAL CARE IS NEEDED TO CALCULATE THE DOSAGE ON THE BASIS OF LEAN BODY-WEIGHT. FOR FURTHER DETAILS, SEE UNDER EFFECTS ON THE EYES IN CHLOROQUINE. IN CHILDREN, THE MINIMUM EFFECTIVE DOSE SHOULD BE USED UP TO A MAXIMUM OF 6.5 MG/KG DAILY (OR 400 MG DAILY WHICHEVER IS THE SMALLER).
HYDROXYCHLOROQUINE SULFATE IS ALSO USED IN SIMILAR DOSES FOR THE TREATMENT OF LIGHT-SENSITIVE SKIN ERUPTIONS, BUT TREATMENT SHOULD ONLY BE GIVEN DURING PERIODS OF MAXIMUM EXPOSURE TO LIGHT.
HYDROXYCHLOROQUINE SULFATE MAY BE USED IN MALARIA BOTH FOR TREATMENT AND PROPHYLAXIS, WHEN CHLOROQUINE IS NOT AVAILABLE, WITH THE SAME LIMITATIONS AS FOR CHLOROQUINE. IN THE USA, A LICENSED DOSE FOR PROPHYLAXIS OF MALARIA IS 400 MG EVERY 7 DAYS; CHILDREN MAY BE GIVEN A WEEKLY PROPHYLACTIC DOSE OF 6.5 MG/KG (UP TO A MAXIMUM OF 400 MG). IN TREATING AN ACUTE MALARIAL ATTACK, A DOSE OF 800 MG HAS BEEN USED, FOLLOWED AFTER 6 TO 8 HOURS BY 400 MG AND A FURTHER 400 MG ON EACH OF THE 2 FOLLOWING DAYS; ALTERNATIVELY, A SINGLE DOSE OF 800 MG HAS BEEN GIVEN. IN CHILDREN, AN INITIAL DOSE OF 13 MG/KG MAY BE GIVEN, FOLLOWED BY 6.5 MG/KG AFTER 6 HOURS AND AGAIN ON THE SECOND AND THIRD DAYS. HYDROXYCHLOROQUINE HAS BEEN DESCRIBED BY SOME AS AN ANTIPLATELET AGENT AND ALTHOUGH ITS MECHANISM OF ACTION IS UNCERTAIN THE INCIDENCE OF FATAL PULMONARY EMBOLISM HAS BEEN REDUCED IN PATIENTS GIVEN HYDROXYCHLOROQUINE PROPHYLACTICALLY AFTER TOTAL HIP REPLACEMENT; THE USUAL DAILY DIVIDED DOSE WAS ABOUT 800 MG FROM THE DAY BEFORE SURGERY UNTIL DISCHARGE; LARGER DOSES HAD BEEN USED.