Phentermine and Venlafaxine interaction
Phentermine and Venlafaxine: both prescribing labels describe an interaction that usually calls for monitoring, a dose change, or spacing the doses.
Usually manageable with monitoring or a dose change. Tell your pharmacist you take both.
What the FDA labels say
From the Venlafaxine (Venlafaxine Hydrochloride) label · effective 2025-01-31
The risk is increased with concomitant use of other serotonergic drugs (including triptans, tricyclic antidepressants, fentanyl, lithium, tramadol, tryptophan, meperidine, methadone, busipirone, amphetamines, and St.
Monoamine Oxidase Inhibitors (MAOIs) [See Dosage and Administration ( 2.6 and 2.7 ), Contraindications ( 4.1 ), and Warnings and Precautions ( 5.2 ) . ] 7.10 Other Serotonergic Drugs The concomitant use of serotonergic drugs (including other SNRIs, SSRIs, triptans, tricyclic antidepressants, opioids, lithium, buspirone, amphetamines, tryptophan, and St.
The safety and efficacy of venlafaxine therapy in combination with weight loss agents, including phentermine, have not been established.
Drug-Laboratory Test Interactions False-positive urine immunoassay screening tests for phencyclidine (PCP) and amphetamine have been reported in patients taking venlafaxine.
Confirmatory tests, such as gas chromatography/mass spectrometry, will distinguish venlafaxine from PCP and amphetamine.
From the Phentermine (Phentermine hydrochloride) label · effective 2026-08-17
The safety and efficacy of combination therapy with phentermine and any other drug products for weight loss including prescribed drugs, over-the-counter preparations, and herbal products, or serotonergic agents such as selective serotonin reuptake inhibitors (e.g., fluoxetine, sertraline, fluvoxamine, paroxetine), have not been established.
Taking more than these two? Interactions stack. Check your whole list at once; it stays in your browser.
Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.