The effects of oral hydralazine on blood pressure, cardiac output and peripheral resistance with respect to dose, age and acetylator status.

Cardiovascular responses are reported in 21 patients with carcinoma of the bronchus taking part in a study of tumour perfusion. There were eight slow and 12 fast acetylators; acetylator status was not determined in one patient with a history of sulphonamide allergy. Hydralazine dose ranged from 25 to 150 mg orally (equivalent to 0.37 to 2.86 mg/kg). Mean arterial blood pressure fell from 98 mmHg before hydralazine to 90 mmHg 60 min after hydralazine (p = 0.002) and mean cardiac output rose from 5.53 l/min to 7.75 l/min (p = 0.00005). Calculated total peripheral resistance fell by 30% (p = 0.0002). Falls in peripheral resistance per milligram hydralazine administered were greater in patients over 70 years of age. Acetylator status was a poor predictor of response. Side-effects were reported by eight patients and were related to the magnitude of fall in peripheral resistance (p = 0.0005) but not to falls in blood pressure (p = 0.12).