A dose-response study of orally administered clonidine as premedication in the elderly: evaluating hemodynamic safety

Clonidine premedication in a dose of 5 micrograms/kg may be particularly well suited for elderly patients. To pursue this approach, sedation, intraocular pressure (IOP), and the hemodynamic profile of two doses of oral clonidine premedication were compared in 60 elderly patients, aged 65-82 yr, who underwent elective ophthalmic surgery under local anesthesia. Group 1 (n = 20) received placebo, Group 2 (n = 20) 150 micrograms of clonidine (2-2.5 micrograms/kg), and Group 3 (n = 20) 300 micrograms of clonidine (4-4.5 micrograms/kg) in a randomized, double-blind fashion. Decreases in mean arterial blood pressure were more pronounced and occurred earlier after 300 micrograms of clonidine (31.4 +/- 12.1%, P < 0.001) as compared to 150 micrograms of clonidine (18.1 +/- 10.9%, P < 0.001). Throughout the study, six patients (30%) in Group 3 (300 micrograms clonidine-treated group), but no patient in Groups 1 or 2, were treated at least once for hypotension (P < 0.05). Heart rate decreased significantly 18.5 +/- 8.1% (P < 0.001) only after 300 micrograms of clonidine. Clonidine 150 micrograms and 300 micrograms decreased IOP 32.1 +/- 14.3% (P < 0.001) and 47.8 +/- 17.2% (P < 0.001), respectively. After 150 micrograms of clonidine patients were significantly more sedated as compared to those given placebo (P < 0.01) but significantly less sedated than after 300 micrograms of clonidine (P < 0.01), where sedation persisted more than 6 h postoperatively.(ABSTRACT TRUNCATED AT 250 WORDS)