Does captopril exacerbate psoriasis?

blood biochemical values were: urea 21-2 mmol/l, creatinine 428 limol/l, sodium 143 mmol/l, chloride 112 mmol/l, potassium 7-2 mmol/l. Muscle cramps due to dehydration and hyperkalaemia were diagnosed and his diuretics and captopril were stopped. He was treated with an insulin-dextrose infusion and calcium resonium. Over the next two days his cramps improved considerably and his serum potassium concentration fell to 4-8 mmol/l. He was restarted on frusemide 40 mg/day and 10 days later was ready for discharge with good control of his heart failure. Biochemical values then were: urea 14-8 mmol/l, creatinine 311 ,umol/l, sodium 142 mmol/l, chloride 105 mmol/l, potassium 4 0 mmol/l. This case highlights the potentially dangerous interaction between angiotensin converting enzyme in-hibitors and potassium sparing diuretics and the resultant rise in serum potassium concentration. Administration ofcaptopril to patients taking diuretics causes a rise in serum potassium concentration.' This is associated with a fall in circulating aldosterone values2 and reduced potassium loss from the distal tubule. Captopril and other angiotensin converting enzyme inhibitors block the production of angio-tensin II, which is the main stimulant to aldosterone release. Concurrent administration of potassium sparing diuretics or potassium supplements with captopril has been associated with hyperkalaemia.23 This was probably the cause in our patient, with his mild chronic renal failure also contributing, as captopril causes a rise in serum potassium values in chronic renal failure.'4 The large dose of potassium sparing diuretic was probably also important. Hyperkalaemia with angiptensin converting enzyme inhibitors and potassium sparing diuretics is well recognised, but with combined preparations ofpotassium sparing and losing diuretics this interaction may be overlooked. Further confusion may arise with Frusene or similarly named preparations as these could potentially be mistaken for plain frusemide. This interaction may be so serious3 that practitioners should have a clear knowledge of patients' diuretic or other treatment when initiating treatment with angiotensin converting enzyme inhibitors, and this risk should be borme in mind. hypokalaemia in uncomplicated systemic hypertension: effect of captopril on blood pressure, plasma potassium and ven-tricular ectopic activity. azotemic patients during angiotensin-converting enzyme inhibition and aldosterone reduction with captopril. Am J Med 1982;73:719-25. 3 Packer M, Lee WH. Provocation of hyper-and hypokalemic sudden death during treatment with and withdrawal of converting enzyme inhibition in severe chronic congestive heart failure.