How long does morphine work?

Morphine’s effect lasts for several hours, and the exact duration depends on how it’s given and the formulation:

- IV morphine: about 3–5 hours (sometimes up to ~6 hours)
- Subcutaneous or intramuscular morphine: about 4–6 hours
- Oral immediate-release morphine: about 4–6 hours
- Oral extended-release (long-acting) morphine: about 8–12 hours (often dosed every 8–12 hours; can be up to 24 hours for some products)
- Epidural morphine: relief can last roughly 12–24 hours, but varies

Individual factors that can change duration:
- Kidney or liver function (active metabolites can accumulate and extend effect)
- Age (older adults may metabolize more slowly)
- Tolerance from prior opioid use
- Other medications and overall health

If you’re asking about a specific route or product, tell me which one and I can give a more precise range. If this is for a patient, consult a clinician for dosing and safety guidance.