Oral Clonidine Reduces Thiamylal Requirement for Induction of Anesthesia in Adult Patients

Although preanesthetic clonidine, an α-2 agonist, is known to reduce anesthetic requirements, the effect of preanesthetic oral clonidine medication per se on the requirement of thiamylal in adult humans has not yet been examined. One hundred and sixty-one adult patients (14–78 years of age) were randomly assigned to groups that received oral clonidine (5μg·kg−1 (n=51), 2.5μg·kg−1 (n=55), or none (n=55)) in addition to 20mg oral famotidine 90min before anesthesia induction. Thiamylal was injected at the rate of 25mg every 15 s until the eyelash reflex disappeared, while blood pressure and heart rate were recorded at 30-s intervals from the start of the induction. Thiamylal requirements were significantly less in both clonidine groups (2.95±0.09 and 3.14±0.10 mg·kg−1 (mean±SE) for patients receiving 5μg·kg−1 and 2.5μg·kg−1 clonidine, respectively) than in the control group (3.81±0.11 mg·kg−1,P<0.05); however, no difference was found between the two clonidine groups. Although mean blood pressure and heart rate during the study period were significantly lower in both clonidine groups than in the control group, no profound hypotension or marked bradycardia were noted in the clonidine groups.