Minor
Probable
Description
Hydroxychloroquine has intrinsic insulin-sensitising properties that may augment the glucose-lowering effect of metformin, occasionally producing hypoglycaemia.
Mechanism
Hydroxychloroquine inhibits insulin degradation in lysosomes and may improve insulin receptor sensitivity; combined with metformin's suppression of hepatic glucose output, additive hypoglycaemia can occur.
Clinical Significance
Clinical studies in diabetic patients with rheumatoid arthritis show improved glycaemic control with hydroxychloroquine, occasionally necessitating metformin dose reduction.
Management
Monitor blood glucose more closely when starting or stopping hydroxychloroquine; consider reducing antidiabetic drug doses if hypoglycaemia occurs.