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A plain-language summary of the cited sources below. Informational only — not medical advice.
Venlafaxine works by slowing the removal of certain chemical messengers in the brain — primarily serotonin and norepinephrine, and at higher doses, dopamine. When these messengers stay active longer in the gaps between nerve cells, mood can improve. It's prescribed for major depressive disorder, including to help prevent depression from returning after someone has recovered.
The medication comes in immediate-release and extended-release forms, which affect how long it stays active in the body. The extended-release version stays in the system longer. Venlafaxine is broken down mainly by an enzyme called CYP3A4, and it also produces an active metabolite (a substance the body converts it into) that continues working after the original medication is processed.
Your family member may experience increases in blood pressure or heart rate while taking venlafaxine. Some people also notice changes in cholesterol or triglyceride levels during treatment. Sexual dysfunction and pupil dilation (mydriasis) have been reported. Serious but less common effects include seizures, elevated blood pressure that needs immediate treatment, and life-threatening bleeding. Venlafaxine can also cause low sodium levels in the blood or a condition called serotonin syndrome, which is potentially life-threatening and involves too much serotonin building up in the body.
Venlafaxine must not be combined with monoamine oxidase inhibitors (MAOIs), reversible MAOIs like moclobemide, linezolid, or intravenous methylene blue. If your family member has been taking a MAOI, they need to wait at least 14 days before starting venlafaxine; if stopping venlafaxine to start a MAOI, they need to wait at least 7 days. The medication is also contraindicated for anyone with a known allergy to venlafaxine or its inactive ingredients.
Common off-label uses observed in AU practice — none of these are TGA-approved indications for this substance. If the documented purpose is one of these, the prescription falls outside the TGA-approved set and may sit inside the chemical-restraint frame depending on jurisdiction and context.
These are practitioner observations, not TGA-approved indications. A use being off-label does not by itself imply a regulated restrictive practice; review the documented purpose against the observed function in context.
Major depressive disorders Clinical criteria: The condition must be stable for the prescriber to consider the listed maximum quantity of this medicine suitable for this patient.
“Non-clinical studies have shown that desvenlafaxine is a selective serotonin and noradrenaline reuptake inhibitor (SNRI).”
“The mean terminal half-life (t 1/2 ) is approximately 11 hours.”
“In vitro studies showed that CYP3A4 is the predominant cytochrome P450 isozyme mediating the oxidative metabolism (N-demethylation) of desvenlafaxine.”
A plain-language summary of the cited sources below. Informational only — not medical advice.
Venlafaxine is a serotonin-norepinephrine reuptake inhibitor (SNRI) indicated for the treatment of major depressive disorder, including relapse prevention. It is a synthetic phenethylamine bicyclic derivative that blocks the reuptake of serotonin and norepinephrine at synaptic transporters; at higher doses it weakly inhibits dopamine reuptake, and because the frontal cortex relies on norepinephrine transporters for dopamine clearance, venlafaxine can enhance dopaminergic neurotransmission in that region. Its active metabolite, desvenlafaxine, is also a selective SNRI and is primarily metabolised via CYP3A4-mediated N-demethylation. The terminal half-life is approximately 11 hours for the active metabolite, with the parent compound showing a half-life of 5±2 hours for immediate-release and 15±6 hours for extended-release formulations.
Common adverse effects include increases in blood pressure and heart rate, small increases in lipid parameters (total cholesterol, LDL, triglycerides), mydriasis, and sexual dysfunction. Serious adverse effects reported include serotonin syndrome or neuroleptic malignant syndrome-like reactions, seizures, life-threatening haemorrhages, hypertensive crises requiring immediate treatment, and hyponatraemia or SIADH. Venlafaxine is contraindicated in patients with hypersensitivity to venlafaxine, desvenlafaxine, or formulation excipients, and must not be used concurrently with monoamine oxidase inhibitors or within 14 days of MAOI discontinuation; conversely, venlafaxine must be ceased for at least 7 days before initiating MAOI therapy.
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Curated subset. The full adverse-effect list is in the TGA Product Information; click any citation above to open it.