Sedative and cardiovascular effects of clonidine and nitrazepam.

Five healthy male subjects, aged 26 to 35 yr, received single oral doses of clonidine 0.3 mg, nitrazepam 20 mg, or placebo double-blind with an interval of at least 1 wk between each treatment. Clonodine induced a maximal fall in systo9lic blood pressure from 104.2 +/- 1.6 to 84.7 +/- 1.4 mm Hg (mean +/- SEM) after 3.5 hr and nitrazepam from 102.9 +/- 1.9 to 90.3 +/- 2.6 mm Hg after 1.0 hr while after placebo blood pressure rose steadily from 102.5 +/- 2.9 to 109.6 +/- 3.5 mm Hg at the end of the 8-hr study. Total sleep time increased from 90.3 +/- 2.5. min after placebo to 256.2 +/0 21.0 min after clonidine (p < 0.001) and 281.0 +/- 40.3 min after nitrazepam (p < 0.001). Stage I sleep increased from 49.7 +/- 11.2 to 76.9 +/- 10.2 min after clonidine and to 76.3 +/- 25.2 min after nitrazepam (p < 0.0), while the greatest increase was observed in stage II: 230.7 +/- 25.6 min after clonidine and 236.6 +/- 35.4 min after nitrazepam compared with only 48.5 +/- 15.8 min after placebo (p < 0.001). Plasma norepinephrine did not change after placebo but fell after nitrazepam from 0.28 +/- 0.04 to 0.14 +/- 0.02 ng/ml after 3 hr (p < 0.05) and after clonidine from 0.23 +/- 0.07 to 0.07 +/- 0.02 ng/ml after 2 hr (p < 0.01). Clonidine and nitrazepam both induced similar hypnotic and hypotensive effects with some evidence that this might be due to a reduction in sympathetic tone.