Low-dose oral chloroquine in patients with porphyria cutanea tarda and low-moderate iron overload

Abstract

Objective: to assess the efficacy, tolerance and determinants for relapse in patients with porphyria cutanea tarda treated with low-dose oral chloroquine. Design: open trial with a median follow-up of 3 years. Setting: outpatient referral unit of a university hospital. Patients: 53 patients with low-moderate iron overload or intolerance to phlebotomies. Intervention: 250 mg twice weekly oral chloroquine diphosphate until remission or failure to respond. Measurements: porphyrin excretion, biochemical changes and development of side effects. Results: after administration of a median dose of 23.5 g of chloroquine (limits 12.6–56 g) during a median time of 8 months (limits: 1–26 months), 50 patients (94%) reached a metabolic remission (urinary uroporphyrin excretion < 100 μg/l). In 14 of these patients (28%), porphyrin excretion further decreased after finishing chloroquine therapy. Metabolic remission persisted during 24 months (limits 6–97 months). Side-effects (severe pruritus) appeared only in one patient. Twenty-two patients relapsed, the relapses being associated with greater basal values of serum AST, ALT, gammaglobulin, urinary uroporphyrin and to the time needed to achieve remission. One year and three years after finishing therapy the probabilities of relapse were 12% (95% C.I.: 5–27%) and 49% (95% C.I.: 34–67%), respectively. Time to achieve remission was the only independent predictor of relapse (hazard ratio: 1.2, 95% C.I.: 1.05–1.21, P < 0.01). Conclusion: low-dose oral chloroquine is a safe therapy that promotes a high proportion of remission and sustained control of porphyria cutanea tarda associated with low-moderate iron overload.