Venlafaxine in divided doses - a case report

Venlafaxine is a drug with at least two significant antidepressant mechanisms of action. Selective serotonin reuptake inhibition (5-HT) is observed even when low doses are used and noradrenalin reuptake inhibition can be seen when doses are higher. The cut-off point is usually a daily dose of 225 mg although a change from one mechanism of action into dual action is usually of spectral nature. It is possible that in daily doses higher than 375 mg, the drug exhibits dopaminergic effects, but such large doses are not recommended by the manufacturer. Using higher doses is associated with greater antidepressant efficacy. One should remember, however, that a change of dosage can be related to a different profile of adverse effects (which also depends on patient's individual sensitivity). The serotoninergic effects are also perceived as sedating, causing excessive drowsiness or even apathy. The noradrenergic effects can, however, evoke the feeling of excessive agitation and sleep disorders. Moreover, the perception of a given action, as indifferent or troublesome to functioning, depends on the time of a day at which it occurs. The sleep-inducing action is perceived as positive by patients in the evening and agitation may be considered positive in the morning. It seems that the time of using venlafaxine may affect the subjective drug tolerance. The article presents two cases that represent this viewpoint. It is not entirely clear why the action of the drug is experienced as the strongest by patients soon after administration (a specific placebo effect cannot be excluded). Despite this, subjective venlafaxine tolerance is undoubtedly associated with the manner of administration. Physicians should take this into consideration.