To the Editor.— A patient I recently saw illustrates the importance of proper instruction regarding route of administration for a given medication and the importance of reinforcing package labeling to ensure proper drug administration and use. Report of a Case.— A 46-year-old man was referred to our hypertension clinic for blood pressure that was difficult to control. He previously had received a complete evaluation to rule out secondary causes of hypertension; results of this workup were negative. The referring physician had prescribed acebutolol, 400 mg twice daily, and a nitroglycerin transdermal patch, 5 cm2(2.5 mg/d), for control of his blood pressure. In the course of obtaining his medical history, the patient stated that he had been taking the nitroglycerin patch orally on a once-a-day basis for the first three days it was prescribed. On each of three occasions, approximately 20 to 30 minutes after ingestion of the patch