Drug interactions
Carbidopa-entacapone-levodopa + Diphenhydramine
Severity: Moderate
Carbidopa-entacapone-levodopa and Diphenhydramine: 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 has anticholinergic and sedative effects that can worsen confusion, hallucinations and drowsiness in patients taking levodopa. Its anticholinergic action may also delay gastric emptying and reduce levodopa absorption.
What this interaction means in plain words
Carbidopa-entacapone-levodopa and Diphenhydramine 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.
Carbidopa-entacapone-levodopa belongs to Central Nervous System; Diphenhydramine belongs to Respiratory.
Why it happens
Additive anticholinergic and sedative effects with possible delayed levodopa absorption.
What to do
Monitor for cognitive effects, sedation and motor fluctuations, particularly in older adults. Avoid regular use and choose a less sedating non-anticholinergic antihistamine where possible.
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?
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Other interactions of Carbidopa-entacapone-levodopa
- Carbidopa-entacapone-levodopa + Isocarboxazid Contraindicated
- Carbidopa-entacapone-levodopa + Phenelzine Contraindicated
- Carbidopa-entacapone-levodopa + Selegiline transdermal Contraindicated
- Carbidopa-entacapone-levodopa + Tranylcypromine Contraindicated
- Amisulpride + Carbidopa-entacapone-levodopa Major
- Asenapine transdermal + Carbidopa-entacapone-levodopa Major
Other interactions of Diphenhydramine
Frequently asked questions
Can I take Carbidopa-entacapone-levodopa with Diphenhydramine?
MediHelp rates the interaction as moderate. Carbidopa-entacapone-levodopa and Diphenhydramine 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 has anticholinergic and sedative effects that can worsen confusion, hallucinations and drowsiness in patients taking levodopa. Its anticholinergic action may also delay gastric emptying and reduce levodopa absorption.
How serious is the interaction between Carbidopa-entacapone-levodopa and Diphenhydramine?
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 cognitive effects, sedation and motor fluctuations, particularly in older adults. Avoid regular use and choose a less sedating non-anticholinergic antihistamine where possible.
What other medicines interact with Carbidopa-entacapone-levodopa?
MediHelp also lists interactions of Carbidopa-entacapone-levodopa with, for example, Isocarboxazid, Phenelzine, Selegiline transdermal. The full list is on the Carbidopa-entacapone-levodopa page.
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