Drug interactions
Diphenhydramine + Phendimetrazine
Severity: Minor
Diphenhydramine and Phendimetrazine: minor interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Phendimetrazine is a stimulant anorectic, while diphenhydramine is sedating, so their effects on alertness oppose one another and the net result is unpredictable. Stimulant effects may mask sedation without improving psychomotor safety.
What this interaction means in plain words
Diphenhydramine and Phendimetrazine have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised.
Why it happens
Opposing pharmacodynamic effects on CNS arousal; no established pharmacokinetic interaction.
What to do
No routine change is needed. Counsel the patient that perceived alertness may not reflect actual performance when driving.
What to ask your pharmacist
- Is there anything I should notice while taking both?
- Do I need to tell my doctor at the next visit?
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Other interactions of Diphenhydramine
Frequently asked questions
Can I take Diphenhydramine with Phendimetrazine?
MediHelp rates the interaction as minor. Diphenhydramine and Phendimetrazine have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised. Phendimetrazine is a stimulant anorectic, while diphenhydramine is sedating, so their effects on alertness oppose one another and the net result is unpredictable. Stimulant effects may mask sedation without improving psychomotor safety.
How serious is the interaction between Diphenhydramine and Phendimetrazine?
MediHelp rates it minor, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: No routine change is needed. Counsel the patient that perceived alertness may not reflect actual performance when driving.
What other medicines interact with Diphenhydramine?
MediHelp also lists interactions of Diphenhydramine with, for example, Alfentanil, Belladonna and opium, Benzhydrocodone / acetaminophen. The full list is on the Diphenhydramine page.
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