Drug interactions
Diphenhydramine + Methocarbamol
Severity: Moderate
Diphenhydramine and Methocarbamol: moderate 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 is a strongly sedating first-generation antihistamine, often used as a sleep aid. With methocarbamol it can cause more drowsiness, dizziness and psychomotor impairment, and confusion and falls in older adults.
What this interaction means in plain words
Diphenhydramine and Methocarbamol can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Diphenhydramine belongs to Respiratory; Methocarbamol belongs to Musculoskeletal.
Why it happens
Additive CNS depression from a sedating antihistamine and a centrally acting muscle relaxant.
What to do
Monitor for oversedation and counsel against driving; avoid in older adults where possible. Use a non-sedating antihistamine if antihistamine therapy is needed.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Diphenhydramine and Methocarbamol, the additional notes, the evidence detail and the whole-prescription interaction checker.
- Full clinical management advice
- Additional notes
- Evidence detail
- Interaction checker for a whole prescription
Try Pro+ free for 7 days on the web. No card needed.
Other interactions of Methocarbamol
Other interactions of Diphenhydramine
Frequently asked questions
Can I take Diphenhydramine with Methocarbamol?
MediHelp rates the interaction as moderate. Diphenhydramine and Methocarbamol can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Diphenhydramine is a strongly sedating first-generation antihistamine, often used as a sleep aid. With methocarbamol it can cause more drowsiness, dizziness and psychomotor impairment, and confusion and falls in older adults.
How serious is the interaction between Diphenhydramine and Methocarbamol?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor for oversedation and counsel against driving; avoid in older adults where possible. Use a non-sedating antihistamine if antihistamine therapy is needed.
What other medicines interact with Methocarbamol?
MediHelp also lists interactions of Methocarbamol with, for example, Alfentanil, Amobarbital, Belladonna and opium. The full list is on the Methocarbamol page.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.
