Anti-ischemic effects of first and second dose of 20 mg isosorbide dinitrate administered 5 hours apart: attenuation of effects despite rising plasma concentration.

Based on evidence that there may be early tolerance development even within the first daily cycle of treatment, this study was undertaken to evaluate the duration and extent of the antiischemic effects of two 20 mg doses of isosorbide dinitrate as used in a well-established regimen documented to maintain effectiveness during long-term treatment. Ischemia parameters were analyzed at 2 and 4 1/2 hours after the first dose as well as at 2 and 7 hours after the second dose given 5 hours later. The studies were performed in 10 male patients with documented coronary artery disease using bicycle ergometry and a double-blind, randomized, placebo-controlled, crossover protocol. ST-segment depression was reduced by 59% (p < 0.0005) at 2 hours and by 42% (p < 0.01) at 4 1/2 hours after the first tablet and by 38% (p < 0.005) at 2 hours and by 15% (p < 0.05) at 7 hours after the second tablet. Increments in ischemia-free workload capacity amounted to 112% (p < 0.005) and to 41% (p < 0.05) after the first tablet and 68% (p < 0.05) and 38% (p < 0.05) at 2 and 7 hours after the second tablet. At 2 and 4 1/2 hours after the first tablet, plasma concentrations of isosorbide dinitrate were 8.4 and 5.9 ng/ml, and those of isosorbide-5-mononitrate were 166.6 and 130.3 ng/ml. At 2 and 7 hours after the second tablet, the concentrations of isosorbide dinitrate were 9.1 and 5.9 ng/ml, and those of isosorbide-5-mononitrate were 224.5 and 148.1 ng/ml.(ABSTRACT TRUNCATED AT 250 WORDS)

RCT Entities:   Population Interventions Outcomes