Pharmacotherapeutic profile of venlafaxine.
When selecting an antidepressant, a number of factors must be considered. These considerations are summarized under the mnemonic STEPS: Safety, Tolerability, Efficacy, Payment (eg, cost-effectiveness), and Simplicity of use. Venlafaxine is the first of a new class of antidepressants that selectively blocks the serotonin and noradrenaline uptake pumps without blocking muscarinic, histaminergic and adrenergic receptors or inhibiting sodium fast channels. Because venlafaxine avoids these mechanisms of action, it has a wide therapeutic index, an improved tolerability profile and a reduced risk of causing pharmacodynamically mediated drug-drug interactions when compared to tricyclic antidepressants (TCAs). In contrast to some other new antidepressants, venlafaxine also avoids effects on cytochrome P450 which are likely to cause clinically meaningful, pharmacokinetically mediated drug-drug interactions. The effects on the uptake pumps of both serotonin and noradrenaline appear to be responsible for some of venlafaxine's unique features in terms of antidepressant efficacy, including its ascending antidepressant dose-response curve and its apparent rapid onset of antidepressant action at the upper end of its clinically relevant dosing range. Venlafaxine is effective in a broad spectrum of patients, including outpatients and inpatients, those with and without melancholia, patients with symptoms of anxiety or agitation or retardation and patients with first time or recurrent episodes of major depression. An important factor when selecting an antidepressant is the simplicity of the dosing regimen and the ability to rapidly and confidently achieve the optimal dose for the patient. In this regard, venlafaxine can be initiated at a clinically effective dose from the beginning. If the patient fails to respond to this dose, there is evidence that increased antidepressant efficacy can be achieved by increasing the dose rather than having to resort to an augmentation strategy or switch to another class of antidepressants. In the immediate release form, venlafaxine has proven antidepressant efficacy when using a twice-or three-times-a-day schedule. A sustained release formulation is expected to be marketed soon and will permit once-a-day-dosing.
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