Studies on hydralazine

Summary

After oral administration of a single 50 mg dose of hydralazine (Apresoline^®), the serum half-life (T1/2) and bioavailability (AUC_0−∞) were assessed in 16 healthy volunteers. The half-life was 2.57±0.14 h (S.E.) in 10 slow acetylators of sulphadimidine, and 2.18±0.15 h in 6 fast acetylators (difference not statistically significant). AUC_0−∞ was significantly higher in slow acetylators, at 1.04±0.10 µg·hour·ml⁻¹, compared to 0.66±0.12 µg·hour·ml⁻¹ in the fast acetylators (p<0.025). Treatment with Apresoline^® 25 mg tid produced minimum serum concentrations at steady-state of 57.3±7.3 ng·ml⁻¹ and 33.4±4.2 ng·ml⁻¹ in 8 slow and 5 fast acetylators, respectively (p<0.05). The corresponding maximum concentrations were 228.8±20.3 ng·ml⁻¹ and 147.6±15.0 ng·ml⁻¹ in slow and fast acetylators, respectively (p<0.025). First-pass metabolism of hydralazine could explain the difference in bioavailability of the drug between fast and slow acetylators, without any corresponding difference in the elimination rate of the drug in the post-distributive phase.