Drug interactions
Morphine + Primidone
Severity: Major
Morphine and Primidone: major interaction.
Last updated 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, so combining it with morphine produces additive sedation and respiratory depression. Concurrent use can cause profound drowsiness and impaired psychomotor function.
What this interaction means in plain words
Morphine 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.
Morphine belongs to Musculoskeletal; Primidone belongs to Central Nervous System.
Why it happens
Additive CNS depression from opioid receptor agonism and barbiturate-mediated GABA-A potentiation.
What to do
Use the lowest effective doses and monitor for sedation and respiratory depression, particularly during dose titration. Advise patients to avoid alcohol and other sedatives.
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?
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References
Other interactions of Morphine
- Alvimopan + Morphine Contraindicated
- Isocarboxazid + Morphine Contraindicated
- Morphine + Olanzapine / samidorphan Contraindicated
- Morphine + Phenelzine Contraindicated
- Morphine + Tranylcypromine Contraindicated
- Alfentanil + Morphine Major
Other interactions of Primidone
- Lorlatinib + Primidone Contraindicated
- Lurasidone + Primidone Contraindicated
- Primidone + Ranolazine Contraindicated
- Primidone + Sofosbuvir-velpatasvir-voxilaprevir Contraindicated
- Primidone + Voriconazole Contraindicated
- Abiraterone + Primidone Major
Frequently asked questions
Can I take Morphine with Primidone?
MediHelp rates the interaction as major. Morphine 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, so combining it with morphine produces additive sedation and respiratory depression. Concurrent use can cause profound drowsiness and impaired psychomotor function.
How serious is the interaction between Morphine 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: Use the lowest effective doses and monitor for sedation and respiratory depression, particularly during dose titration. Advise patients to avoid alcohol and other sedatives.
What other medicines interact with Morphine?
MediHelp also lists interactions of Morphine with, for example, Alvimopan, Isocarboxazid, Olanzapine / samidorphan. The full list is on the Morphine page.
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