Phentermine and Phenylephrine interaction
Phentermine and Phenylephrine: both prescribing labels flag this combination with the strongest language, such as a contraindication, a boxed warning, or an instruction to avoid it.
Do not combine without a prescriber's guidance. The label language below is the strongest FDA uses.
What the FDA labels say
From the Phentermine (Phentermine hydrochloride) label · effective 2026-08-17
…states • History of drug abuse • Pregnancy [ see Use in Specific Populations () ] • Nursing [ see Use in Specific Populations ( 8.3 ) ] • Known hypersensitivity, or idiosyncrasy to the sympathomimetic amines • History of cardiovascular disease (e.g., coronary artery disease, stroke, arrhythmias, congestive heart failure, uncontrolled hypertension) () • During or within…
• Known hypersensitivity, or idiosyncrasy to the sympathomimetic amines ( 4 )
From the Phenylephrine (Biorphen) label · effective 2026-03-31
Pressor Effect with Concomitant Oxytocic Drugs Oxytocic drugs potentiate the increasing blood pressure effect of sympathomimetic pressor amines including BIORPHEN [see Drug Interactions (7.1) ] , with the potential for hemorrhagic stroke.
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.