Optimal administration time of intramuscular midazolam premedication

The optimal administration time for intramuscular injection of midazolam as premedication was studied. Sixty patients ranging in age from 40 to 65 were included. A combination of atropine 0.3-0.5 mg and midazolam 0.08 mg·kg(-1) was given to four groups of 15 subjects each in intramuscular injections 45, 30, 15 min, and immediately before entering the operating room. Blood pressure, heart rate, respiratory rate, depression of the root of the tongue, eyelash reflex, degree of sedation, and amnestic effect at the time of arriving the operating room were compared among the groups. There was no difference among the groups in blood pressure, heart rate, and respiratory rate. The depression of the root of the tongue, disappearance of verbal response, and eyelash reflex were found in the 30- and 45-min groups. The degree of sedation and amnestic effect were good except for the group who received midazolam immediately before entering the operating room. From the above results, intramuscular injection of midazolam 0.08 mg·kg(-1) with atropine 0.3-0.5 mg is considered best when administered 15 min before entering the operating room.