Drug interactions
Diphenhydramine + Methamphetamine
Severity: Minor
Diphenhydramine and Methamphetamine: 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 inhibits CYP2D6, which may modestly raise methamphetamine levels, while the stimulant may mask diphenhydramine sedation. The combined effect is usually small but can cause increased stimulant effects or unpredictable alertness.
What this interaction means in plain words
Diphenhydramine and Methamphetamine 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; Methamphetamine belongs to Central Nervous System.
Why it happens
CYP2D6 inhibition by diphenhydramine and opposing CNS effects of a stimulant and a sedating antihistamine.
What to do
No routine dose change is needed; monitor heart rate and blood pressure and counsel about 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 Methamphetamine
- Isocarboxazid + Methamphetamine Contraindicated
- Linezolid + Methamphetamine Contraindicated
- Methamphetamine + Phenelzine Contraindicated
- Methamphetamine + Procarbazine Contraindicated
- Methamphetamine + Rasagiline Contraindicated
- Methamphetamine + Safinamide Contraindicated
Other interactions of Diphenhydramine
Frequently asked questions
Can I take Diphenhydramine with Methamphetamine?
MediHelp rates the interaction as minor. Diphenhydramine and Methamphetamine 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 inhibits CYP2D6, which may modestly raise methamphetamine levels, while the stimulant may mask diphenhydramine sedation. The combined effect is usually small but can cause increased stimulant effects or unpredictable alertness.
How serious is the interaction between Diphenhydramine and Methamphetamine?
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 dose change is needed; monitor heart rate and blood pressure and counsel about driving.
What other medicines interact with Methamphetamine?
MediHelp also lists interactions of Methamphetamine with, for example, Isocarboxazid, Linezolid, Phenelzine. The full list is on the Methamphetamine page.
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