Natural opium alkaloids
ATC code: N02AA01 (Morphine)
Brand names
MS Contin, Avinza, Kadian
Full μ-opioid receptor agonist in the CNS, activating descending pain-inhibitory pathways. Reduces pain perception and emotional response. At therapeutic doses produces analgesia, sedation, euphoria, miosis, and respiratory depression. The comparator for all opioid analgesics — oral morphine 30 mg = 10 mg IV = 100 mg oral codeine. About 5–7 % of Europeans have genetically reduced μ-opioid receptor activity.
First line
Standard for severe acute pain in hospital. IV 2–5 mg every 5–10 minutes to analgesia. In postoperative patients, patient-controlled analgesia (PCA) is used. Per CDC 2022, outpatient courses for acute pain should not exceed 3–7 days.
In severe acute pain (MI, major trauma, postoperative pain) in hospital settings.
First line
First-line for moderate-to-severe cancer pain per Cancer Pain Ladder and ESMO 2018. In cancer patients, opioids are used without upper dose ceiling when properly titrated and tolerated. Opioid-naive starting dose: 5–10 mg orally every 4 hours (immediate release) or 1–2 mg IV. After stabilization, switch to extended-release twice daily. Duration is not capped.
Not recommended
Morphine is not used in mild-to-moderate non-cancer pain. Opioids in chronic non-cancer pain per CDC 2022 are the exception, not the rule. Foundation: paracetamol, NSAIDs, gabapentinoids, antidepressants tailored to pain type, and non-pharmacological measures.
Boxed warning
FDA boxed warning: high risk of addiction, abuse, and severe respiratory depression, especially with benzodiazepines or other CNS depressants. Neonatal exposure can cause withdrawal syndrome. Concomitant alcohol use is potentially fatal.
Long-term use in the third trimester is associated with neonatal abstinence syndrome. In pregnant patients with severe pain, use is justified at the minimum effective dose. In opioid-dependent pregnant women, methadone or buprenorphine maintenance is the standard — not abrupt discontinuation.
Transfers into breast milk in small amounts. Short-term standard-dose use is compatible with breastfeeding per LactMed. Long-term high-dose therapy requires pediatric consultation.
morphine is evaluated for the following indications with varying evidence strength: Chronic cancer pain (evidence tier A), Acute moderate-to-severe pain (evidence tier A), Mild to moderate pain in adults (evidence tier F). See the full indication matrix with dosing and citations above on this page.
Common side effects of morphine (≥ 1 in 100): Constipation (in 90 % of patients), Nausea, vomiting (especially in the first days), Sedation, drowsiness, Pruritus, Dry mouth, Urinary retention. See the Safety section for uncommon and serious reactions.
Long-term use in the third trimester is associated with neonatal abstinence syndrome. In pregnant patients with severe pain, use is justified at the minimum effective dose. In opioid-dependent pregnant women, methadone or buprenorphine maintenance is the standard — not abrupt discontinuation.
Transfers into breast milk in small amounts. Short-term standard-dose use is compatible with breastfeeding per LactMed. Long-term high-dose therapy requires pediatric consultation.
morphine is contraindicated in: Respiratory depression, respiratory failure; Acute or severe bronchial asthma; Paralytic ileus; Acute abdomen of unknown etiology; Concurrent or recent MAOI (within 14 days). Full list in the Safety section.
FDA boxed warning: high risk of addiction, abuse, and severe respiratory depression, especially with benzodiazepines or other CNS depressants. Neonatal exposure can cause withdrawal syndrome. Concomitant alcohol use is potentially fatal.