Drug interactions

Carisoprodol + Primidone

Severity: Major

Carisoprodol and Primidone: major interaction.

Last updated 29 Oct 2026 Sources: US FDA label

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

Primidone is metabolized to phenobarbital, which adds to carisoprodol's sedation. Enzyme induction may also alter carisoprodol metabolism.

What this interaction means in plain words

Carisoprodol and Primidone can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.

Carisoprodol belongs to Musculoskeletal; Primidone belongs to Central Nervous System.

Evidence level: Moderate

Why it happens

Additive CNS depression, with possible CYP induction by primidone and phenobarbital.

What to do

Avoid if possible; otherwise monitor sedation and respiratory status and use the lowest effective carisoprodol dose.

What to ask your pharmacist

Does the benefit of taking both outweigh the risk in my case?
Do I need any blood test, ECG or other check while on both?
What early warning signs should I watch for, and what should I do if they appear?

Bring a full list of your medicines, including over-the-counter products, supplements and herbal remedies, to every pharmacy visit.

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References

Carisoprodol - FDA drug label (DailyMed) - section 7 Drug Interactions (class statement: CNS depressants; "The sedative effects of carisoprodol and other CNS depressants (e.g., alcohol, benzodiazepines, opioids, tricyclic antidepressants) may be additive.") — DailyMed (FDA label)

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Frequently asked questions

Can I take Carisoprodol with Primidone?

MediHelp rates the interaction as major. Carisoprodol and Primidone can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Primidone is metabolized to phenobarbital, which adds to carisoprodol's sedation. Enzyme induction may also alter carisoprodol metabolism.

How serious is the interaction between Carisoprodol and Primidone?

MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid if possible; otherwise monitor sedation and respiratory status and use the lowest effective carisoprodol dose.

What other medicines interact with Carisoprodol?

MediHelp also lists interactions of Carisoprodol with, for example, Alfentanil, Alprazolam, Amobarbital. The full list is on the Carisoprodol page.

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