Melatonin for preoperative and postoperative anxiety in adul
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Anxiety in relation to surgery is a well?known problem. Melatonin offers an alternative treatment to benzodiazepines for ameliorating this condition in the preoperative and postoperative periods. To assess the effects of melatonin on preoperative and postoperative anxiety compared to placebo or benzodiazepines a study was conducted.

Researchers included randomized, placebo?controlled or standard treatment?controlled studies that evaluated the effects of preoperatively administered melatonin on preoperative or postoperative anxiety. Adult patients of both sexes (15 to 90 years of age) undergoing any kind of surgical procedure for which it was necessary to use general, regional, or topical anaesthesia were included. 27 randomized controlled trials (RCTs) were included , involving 2319 participants, that assessed melatonin for treating preoperative anxiety, postoperative anxiety, or both.

24 studies compared melatonin with placebo. 11 studies compared melatonin to a benzodiazepine (7 studies with midazolam, 3 studies with alprazolam, and 1 study with oxazepam). Other comparators in a small number of studies were gabapentin, clonidine, and pregabalin.

No studies were judged to be at low risk of bias for all domains. Most studies were judged to be at unclear risk of bias overall. Eight studies were judged to be at high risk of bias in one or more domain, and thus, to be at high risk of bias overall.

Melatonin probably results in a reduction in preoperative anxiety measured by a visual analogue scale (VAS, 0 to 100 mm) compared to placebo based on a meta?analysis of 18 studies. Melatonin may reduce immediate postoperative anxiety measured on a 0 to 100 mm VAS compared to placebo and may reduce delayed postoperative anxiety measured six hours after surgery using the State?Trait Anxiety

Adverse events: 14 studies did not report on adverse events. 6 studies specifically reported that no side effects were observed, and the remaining 7 studies reported cases of nausea, sleepiness, dizziness, and headache; however, no serious adverse events were reported.

11 studies measured psychomotor and cognitive function, or both, and in general, these studies found that benzodiazepines impaired psychomotor and cognitive function more than placebo and melatonin. 14 studies evaluated sedation and generally found that benzodiazepine caused the highest degree of sedation, but melatonin also showed sedative properties compared to placebo.

When compared with placebo, melatonin given as premedication (as tablets or sublingually) probably reduces preoperative anxiety in adults (measured 50 to 120 minutes after administration), which is potentially clinically relevant. The effect of melatonin on postoperative anxiety compared to placebo (measured in the recovery room and six hours after surgery) was also evident but was much smaller, and the clinical relevance of this finding is uncertain. There was little or no difference in anxiety when melatonin was compared with benzodiazepines. Thus, melatonin may have a similar effect to benzodiazepines in reducing preoperative and postoperative anxiety in adults.