Sedative and cardiovascular effects of clonidine and nitrazepam

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Abstract
Healthy male subjects (5) 26-35 yr old 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. Clonidine induced a maximal fall in systolic blood pressure from 104.2 .+-. 1.6 to 84.7 .+-. 1.4 mm Hg (.hivin.x [mean] .+-. SEM [SE of mean]) after 3.5 h and nitrazepam from 102.9 .+-. 1.9 to 90.3 .+-. 2.6 mm Hg after 1.0 h 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 h study. Total sleep time increased from 90.3 .+-. 25.5 min after placebo to 256.2 .+-. 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 < 0.05), while the greatest increase was observed in stage 11: 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 h (P < 0.05) and after clonidine from 0.23 .+-. 0.07 to 0.07 .+-. 0.02 ng/ml after 2 h (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.