A 16-year-old boy is brought to your office for a routine ex…

A 16-year-old boy is brought to your office for a routine examination. He has had insulin-dependent diabetes for 13 years. He has been well but admits to nocturia and polyuria. His last hemoglobin A1C measurement was 13.2%. Physical examination shows a blood pressure of 142/92 mmHg. The remainder of the examination is unremarkable. Laboratory data show: Hemoglobin A1C = 14.1%, urinalysis specific gravity = 1.035, pH = 6.0, blood negative, sugar > 1000 mg/dl, ketones, trace; protein = 1+. The best class of drug to control his blood pressure would be: