To the Editor.
—Nifedipine is a calcium channel-blocking agent that is being used with increasing frequency for the treatment of ischemic heart disease and hypertension.1-3 Since these are common problems in patients receiving dialysis, it may be anticipated that many such patients will be treated with this drug. We recently saw a patient on continuous ambulatory peritoneal dialysis (CAPD) who had been taking 20 mg of nifedipine four times a day for angina, but were unable to find any published data concerning the use of this drug in this setting. To determine if any dosage modification is necessary, we measured plasma levels and drug removal by peritoneal dialysis.The patient was studied in our CAPD Unit, where multiple dialysis exchanges were performed. Peritoneal fluid samples were collected from the dialysate effluent at the completion of each drainage (time intervals given in the Table) and sent to a laboratory (Pfizer