Drug interactions
Diamorphine + Methocarbamol
Severity: Major
Diamorphine and Methocarbamol: major interaction.
Last updated Sources: UK SmPC
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
Diamorphine (heroin) is a potent opioid, and methocarbamol is a sedating skeletal muscle relaxant. Combined use can produce excessive sedation, slowed breathing and impaired alertness.
What this interaction means in plain words
Diamorphine and Methocarbamol 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.
Why it happens
Additive CNS and respiratory depression from opioid agonism plus methocarbamol's central depressant effect.
What to do
Start with reduced doses and titrate carefully. Monitor sedation level and respiratory rate, and counsel patients to avoid driving and other CNS depressants.
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 Methocarbamol
Frequently asked questions
Can I take Diamorphine with Methocarbamol?
MediHelp rates the interaction as major. Diamorphine and Methocarbamol 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. Diamorphine (heroin) is a potent opioid, and methocarbamol is a sedating skeletal muscle relaxant. Combined use can produce excessive sedation, slowed breathing and impaired alertness.
How serious is the interaction between Diamorphine and Methocarbamol?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Start with reduced doses and titrate carefully. Monitor sedation level and respiratory rate, and counsel patients to avoid driving and other CNS depressants.
What other medicines interact with Methocarbamol?
MediHelp also lists interactions of Methocarbamol with, for example, Alfentanil, Amobarbital, Belladonna and opium. The full list is on the Methocarbamol page.
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