Drug interactions
Diphenhydramine + Loratadine
Severity: Minor
Diphenhydramine and Loratadine: 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 and could slightly raise loratadine exposure. The more relevant concern is that using two antihistamines together adds up antihistaminic and sedative effects, although loratadine contributes little sedation.
What this interaction means in plain words
Diphenhydramine and Loratadine 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; Loratadine belongs to Respiratory.
Why it happens
CYP2D6 inhibition by diphenhydramine and duplicated H1-antihistamine pharmacology.
What to do
Avoid combining two antihistamines unnecessarily. If both are used, monitor for sedation and anticholinergic effects, particularly in older adults.
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 Loratadine
- Acrivastine + Loratadine Moderate
- Amobarbital + Loratadine Moderate
- Fentanyl + Loratadine Moderate
- Isocarboxazid + Loratadine Moderate
- Levoketoconazole + Loratadine Moderate
- Loratadine + Mavacamten Moderate
Other interactions of Diphenhydramine
Frequently asked questions
Can I take Diphenhydramine with Loratadine?
MediHelp rates the interaction as minor. Diphenhydramine and Loratadine 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 and could slightly raise loratadine exposure. The more relevant concern is that using two antihistamines together adds up antihistaminic and sedative effects, although loratadine contributes little sedation.
How serious is the interaction between Diphenhydramine and Loratadine?
MediHelp rates it minor, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid combining two antihistamines unnecessarily. If both are used, monitor for sedation and anticholinergic effects, particularly in older adults.
What other medicines interact with Loratadine?
MediHelp also lists interactions of Loratadine with, for example, Acrivastine, Amobarbital, Fentanyl. The full list is on the Loratadine page.
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