The effects of melatonin premedication on propofol and thiopental induction dose-response curves: a prospective, randomized, double-blind study.
BACKGROUND
The effect of melatonin on the intraoperative requirements for i.v.anesthetics has not been documented. We studied the effect of melatonin premedication on the propofol and thiopental dose-response curves for abolition of responses to verbal commands and eyelash stimulation.


METHODS
This prospective, randomized, double-blind study included 200 adults with ASA physical status I. Patients received either 0.2 mg/kg melatonin or a placebo orally for premedication (n = 100 per group). Approximately 50 min later, subgroups of 10 melatonin and 10 placebo patients were administered various doses of propofol (0.5, 1.0, 1.5, 2.0, or 2.4 mg/kg) or thiopental (2.0, 3.0, 4.0, 5.0, or 6.0 mg/kg) for anesthetic induction. The ability of each patient to respond to the command, "open your eyes," and the disappearance of the eyelash reflex were assessed 60 s after the end of the injection of propofol or thiopental. Dose-response curves were determined by probit analysis.


RESULTS
Melatonin premedication decreased thiopental ED50 values for loss of response to verbal command and eyelash reflex from 3.4 mg/kg (95% confidence interval, 3.2-3.5 mg/kg) and 3.7 mg/kg (3.5-3.9 mg/kg) to 2.7 mg/kg (2.6-2.9 mg/kg) and 2.6 mg/kg (2.5-2.7 mg/kg), respectively (P < 0.05). Corresponding propofol ED50 values decreased from 1.5 mg/kg (1.4-1.6 mg/kg) and 1.6 mg/kg (1.5-1.7 mg/kg) to 0.9 mg/kg (0.8-0.96 mg/kg) and 0.9 mg/kg (0.8-0.95 mg/kg), respectively (P < 0.05).


CONCLUSIONS
Melatonin premedication significantly decreased the doses of both propofol and thiopental required to induce anesthesia.
Naguib
Mohamed
M
Department of Anesthesiology and Pain Medicine, University of Texas M.D. Anderson Cancer Center, Unit 409, 1400 Holcombe Boulevard, Houston, TX 77030, USA. naguib@mdanderson.org
Samarkandi
Abdulhamid H
AH
Moniem
Mohamed A
MA
Mansour
Emad El-Din
Eel-D
Alshaer
Ahmad A
AA
Al-Ayyaf
Hasan A
HA
Fadin
Awatif
A
Alharby
Saleh W
SW
D000293:Adolescent; D000328:Adult; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008550:Melatonin / Q000494:pharmacology*; D008875:Middle Aged; D011292:Premedication; D015742:Propofol / Q000494:pharmacology*; D011446:Prospective Studies; D011963:Receptors, GABA-A / Q000187:drug effects; D013874:Thiopental / Q000494:pharmacology*
D011963:Receptors, GABA-A; D013874:Thiopental; D008550:Melatonin; D015742:Propofol