title: Plasma hydroxychloroquine concentrations and efficacy in rheumatoid arthritis.
abstract: Plasma levels of hydroxychloroquine (HCQ) and its metabolites were measured, by high performance liquid chromatography, in 37 rheumatoid arthritis patients who could be clearly distinguished as responders (n = 28) or nonresponders (n = 9) to HCQ, 400 mg/day. Efficacy in both groups was determined by the patients' erythrocyte sedimentation rates, joint counts, morning stiffness, global assessments, concurrent drug therapies, and grip strength. The response rate was 76%. Responders had a mean HCQ level of 213 ng/ml, versus 306 in nonresponders (P less than 0.05). The mean level of HCQ plus total metabolites in responders was 363 ng/ml, versus 554 in nonresponders (P less than 0.01). We conclude that monitoring plasma HCQ levels is unlikely to be helpful in individualizing effective drug dosage.
mesh_terms: D001172:Arthritis, Rheumatoid / Q000188:drug therapy*; D006801:Humans; D006886:Hydroxychloroquine / Q000097:blood / Q000627:therapeutic use*; D008991:Monitoring, Physiologic
chemical_list: D006886:Hydroxychloroquine