Drug interactions
Diphenhydramine + Modafinil
Severity: Minor
Diphenhydramine and Modafinil: 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
Diphenhydramine causes sedation and psychomotor impairment, while modafinil promotes wakefulness, so the two oppose each other. Modafinil may mask drowsiness without reliably normalising performance.
What this interaction means in plain words
Diphenhydramine and Modafinil have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised.
Diphenhydramine belongs to Respiratory; Modafinil belongs to Central Nervous System.
Why it happens
Opposing pharmacodynamic effects on CNS arousal (H1 blockade versus wake-promoting action).
What to do
Advise caution when driving; consider a non-sedating antihistamine or avoid diphenhydramine as a sleep aid in patients taking modafinil.
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 Modafinil
Other interactions of Diphenhydramine
Frequently asked questions
Can I take Diphenhydramine with Modafinil?
MediHelp rates the interaction as minor. Diphenhydramine and Modafinil have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised. Diphenhydramine causes sedation and psychomotor impairment, while modafinil promotes wakefulness, so the two oppose each other. Modafinil may mask drowsiness without reliably normalising performance.
How serious is the interaction between Diphenhydramine and Modafinil?
MediHelp rates it minor, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Advise caution when driving; consider a non-sedating antihistamine or avoid diphenhydramine as a sleep aid in patients taking modafinil.
What other medicines interact with Modafinil?
MediHelp also lists interactions of Modafinil with, for example, Lenacapavir, Leniolisib, Lorlatinib. The full list is on the Modafinil page.
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