Prophylactic mirtazapine reduces intrathecal morphine-induced pruritus.
BACKGROUND
Activation of the serotonergic system is an important factor in the pathogenesis of intrathecal morphine-induced pruritus. Mirtazapine is a new antidepressant that selectively blocks 5-HT(2) and 5-HT(3) receptors. We therefore tested the hypothesis that preoperative mirtazapine would reduce the incidence of intrathecal morphine-induced pruritus.


METHODS
One hundred and ten ASA I patients undergoing lower limb surgery under spinal anaesthesia were randomly allocated into two equal groups and received either mirtazapine 30 mg or an orally disintegrating placebo tablet 1 h before operation in a prospective, double-blinded trial. All patients received an intrathecal injection of 15 mg of 0.5% isobaric bupivacaine and 0.2 mg preservative-free morphine. The occurrence and the severity of pruritus were assessed at 3, 6, 9, 12, and 24 h after intrathecal morphine.


RESULTS
Pruritus was significantly more frequent in the placebo group compared with the mirtazapine group (75% vs 52%, respectively; P=0.0245). The time to onset of pruritus in the two groups was also significantly different. The patients who experienced pruritus in the placebo group had a faster onset time than that in the mirtazapine group [mean (sd): 3.2 (0.8) vs 7.2 (4.1) h, P<0.0001].


CONCLUSIONS
Mirtazapine premedication prevents pruritus induced by intrathecal morphine in patients undergoing lower limb surgery with spinal anaesthesia.
Sheen
M J
MJ
Department of Anaesthesiology, Tri-Service General Hospital, National Defense Medical Center, 325, Cheng-gong Road Section 2, Neihu, Taipei 11490, Taiwan. mkjsheen@ndmctsgh.edu.tw
Ho
S-T
ST
Lee
C-H
CH
Tsung
Y-C
YC
Chang
F-L
FL
Huang
S-T
ST
D000328:Adult; D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000009:adverse effects*; D000775:Anesthesia, Spinal; D004311:Double-Blind Method; D005260:Female; D006634:Histamine H1 Antagonists / Q000009:adverse effects / Q000627:therapeutic use; D006801:Humans; D007278:Injections, Spinal; D035002:Lower Extremity / Q000601:surgery; D008297:Male; D008803:Mianserin / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000627:therapeutic use; D000078785:Mirtazapine; D009020:Morphine / Q000008:administration & dosage / Q000009:adverse effects*; D011229:Preanesthetic Medication / Q000379:methods; D011446:Prospective Studies; D011537:Pruritus / Q000139:chemically induced / Q000473:pathology / Q000517:prevention & control*; D012702:Serotonin Antagonists / Q000009:adverse effects / Q000627:therapeutic use*; D012720:Severity of Illness Index; D016896:Treatment Outcome
D000701:Analgesics, Opioid; D006634:Histamine H1 Antagonists; D012702:Serotonin Antagonists; D008803:Mianserin; D009020:Morphine; D000078785:Mirtazapine