Yawning is a complex stereotyped behavior with unknown physiological functions. Excessive yawning without a decrease of the arousal level has been noted with various drugs (Sommet et al., 2007). Almost all these treatments have a central nervous system action. Venlafaxine, a selective serotonin and norepinephrine reuptake inhibitor (SNRI), is prescribed for the treatment of major depression and anxiety disorders. Although yawning was an uncommon side effect of venlafaxine during the premarketing and postmarketing clinical trials, no cases of severe and disabling yawning have been reported till now#
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