Isosorbide dinitrate kinetics and dynamics after intravenous, sublingual, and percutaneous dosing in angina

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Abstract
Isosorbide dinitrate (ISDN) kinetics and dynamics were examined after various routes of administration for angina. Given i.v., ISDN kinetics were apparently linear over the range of infusion rate (0.083 and 0.133 mg/min) and duration (15 min and 1 and 2 h) studied. Mean .+-. systemic clearance of ISDN was 3.4 .+-. 1.4 l/min and volume of distribution (Vdss or Vdarea) about 100 l. These data are consistent with the presence of extensive extrahepatic metabolism. In 6 patients, sublingual ISDN (5 mg) was also given and mean bioavailability of 59% (19-93%) for this route was determined. For this group, sublingual absorption of intact ISDN was incomplete and variable. The presence of a longer disappearance t1/2 [half-life] after sublingual dosing suggested that the input process may be rate limiting. After percutaneous application of a topical formulation (100 mg over an area of 400 cm2), steady-state plasma concentrations at about 7 ng/ml were maintained from 6 to 24 h. The bioavailability of the topical application was estimated at 30%. At the doses given, i.v. ISDN had no apparent effect on heart rate but induced significant reduction in standing systolic blood pressure. The effect vs. the ISDN concentration profile was described by a hysteresis loop, indicating that changes in blood pressure response lag behind changes in plasma ISDN concentration. After i.v. dosing, peak plasma ISDN concentration and peak effect (maximum change in standing systolic blood pressure). At the doses used, both sublingual and percutaneous ISDN induced less distinct circulatory changes than the i.v. infusion.