Documented interactions for Phentermine (phentermine). Each entry cites the prescribing information or FDA safety communication it is based on.
| Severity | Interacts with | Class | Concern |
|---|---|---|---|
| Contraindicated | MAO inhibitors (phenelzine, tranylcypromine, linezolid, methylene blue) | Monoamine oxidase inhibitor | Phentermine with MAO inhibitors is contraindicated |
| Contraindicated | MAO inhibitors (phenelzine, tranylcypromine, linezolid, methylene blue) | Monoamine oxidase inhibitor | Stimulant with MAO inhibitors is contraindicated |
| Moderate | Insulin and sulfonylureas | Antidiabetic | Stimulants may alter glucose control |
| Moderate | Other serotonergic drugs (tramadol, SSRIs, SNRIs, triptans, St John's Wort, linezolid) | Serotonergic agent | Stimulant with serotonergic drugs |
| Moderate | Other stimulants (amphetamine, methamphetamine, methylphenidate, phentermine) | CNS stimulant | Additive cardiovascular effects with other stimulants |
| Moderate | Other stimulants (amphetamine, methamphetamine, methylphenidate, phentermine) | CNS stimulant | Additive cardiovascular and psychiatric effects with other stimulants |
With: MAO inhibitors (phenelzine, tranylcypromine, linezolid, methylene blue) Monoamine oxidase inhibitor
Sympathomimetic amines release catecholamines; MAO inhibitors prevent their breakdown.
Extreme hyperadrenergic crisis with hypertension, hyperthermia, and seizures.
Do not combine. A washout period is required.
Basis: Phentermine HCl tablets prescribing information, Contraindications. source
With: MAO inhibitors (phenelzine, tranylcypromine, linezolid, methylene blue) Monoamine oxidase inhibitor
Sympathomimetic amines release catecholamines; MAO inhibitors prevent their breakdown.
Extreme hyperadrenergic crisis with hypertension, hyperthermia, and seizures.
Do not combine; a washout period is required.
Basis: Stimulant prescribing information, Contraindications. source
With: Insulin and sulfonylureas Antidiabetic
Sympathomimetics can raise blood glucose and reduce insulin effect.
Labeling notes that insulin or oral hypoglycemic dosages may need adjustment in some patients.
Monitor blood glucose more frequently if you have diabetes.
Basis: Phentermine HCl tablets prescribing information, Drug Interactions. source
With: Other serotonergic drugs (tramadol, SSRIs, SNRIs, triptans, St John's Wort, linezolid) Serotonergic agent
Additive serotonergic activity.
Serotonin syndrome is possible.
Disclose antidepressants to the prescriber.
Basis: Stimulant prescribing information, Warnings. source
With: Other stimulants (amphetamine, methamphetamine, methylphenidate, phentermine) CNS stimulant
Additive sympathomimetic activity.
Increased risk of tachycardia, hypertension, and insomnia.
Prescribers monitor blood pressure and heart rate.
Basis: Phentermine HCl tablets prescribing information, Warnings and Precautions. source
With: Other stimulants (amphetamine, methamphetamine, methylphenidate, phentermine) CNS stimulant
Additive sympathomimetic activity.
Tachycardia, hypertension, insomnia, agitation.
Monitor blood pressure and heart rate.
Basis: Stimulant prescribing information, Warnings and Precautions. source
We have documented 6 interaction classes for Phentermine in our dataset. Usually avoided, or used only with explicit prescriber oversight and close monitoring. The most serious items on this page are marked contraindicated or major.
Alcohol interacts with most of the medications on this site because it adds to sedation and slows breathing. For the specific documented risk, see the relevant entry above. The general rule from labeling is to avoid alcohol.
No. An empty result only means our curated dataset has no matching rule. A pharmacist can run a full interaction screen against every medication and supplement you take.
This site provides educational information only and does not sell, prescribe or dispense medications. Always consult a licensed healthcare provider. This page is not medical advice.