Mst Continus (Q12h) (Morphine Sulfate Ph. Eur.)

Morphine sulfate is an opioid analgesic used to manage pain pathways associated with moderate to severe acute or chronic pain.

• Acute postoperative pain: provides effective relief of severe pain following surgical procedures.
• Cancer‑related pain: controls persistent pain in oncology patients when other analgesics are insufficient.
• Chronic non‑cancer pain: reduces pain intensity in long‑term conditions where alternative therapies have failed.

• Morphine sulfate exerts its analgesic effect by acting as a full agonist at μ‑opioid receptors located in the central nervous system and peripheral tissues. Binding to these G‑protein‑coupled receptors inhibits adenylate cyclase activity, reduces calcium influx, and increases potassium efflux, leading to hyperpolarization of neurons and decreased transmission of nociceptive signals. This results in diminished perception of pain and altered emotional response to painful stimuli.

Morphine sulfate may cause a range of adverse reactions, varying from mild to serious.

Common Side Effects

• Constipation: reduced gastrointestinal motility leading to hard stools.
• Nausea: feeling of sickness often accompanied by vomiting.
• Drowsiness: increased sleepiness or reduced alertness.
• Dry mouth: decreased salivation causing oral discomfort.
• Sweating: excessive perspiration without exertion.

Serious or Rare Side Effects

• Respiratory depression: slowed or shallow breathing that can be life‑threatening.
• Hypotension: significant drop in blood pressure causing dizziness.
• Severe allergic reaction: rash, itching, swelling, or anaphylaxis.
• Dependence and withdrawal: risk of physical dependence with abrupt discontinuation.
• Urinary retention: difficulty emptying the bladder.

When prescribing morphine sulfate, clinicians should consider several safety precautions to minimize risks.

• Assess pain severity: confirm that opioid therapy is appropriate for moderate to severe pain.
• Evaluate patient history: screen for respiratory disorders, head injury, or increased intracranial pressure.
• Monitor for sedation: observe patients for excessive drowsiness or impaired cognition.
• Adjust dose in renal/hepatic impairment: reduce dosage or increase dosing interval as needed.
• Avoid concurrent CNS depressants: limit use with benzodiazepines or alcohol.
• Store at ambient temperature: keep below 25 °C in the original packaging, protected from moisture and light.

Morphine sulfate can interact with other medicines, altering its effectiveness or safety profile.

Major Interactions (Avoid)

• Other opioids: combined use can cause profound respiratory depression.
• CNS depressants (e.g., benzodiazepines, barbiturates): increase risk of sedation and respiratory compromise.
• MAO inhibitors: may precipitate severe hypertension or serotonin syndrome.

Moderate Interactions (Monitor Closely)

• CYP3A4 inhibitors (e.g., ketoconazole, erythromycin): may raise morphine plasma levels.
• CYP3A4 inducers (e.g., rifampin, carbamazepine): may reduce analgesic effect.
• Anticholinergic agents: can worsen constipation.
• Diuretics: may enhance hypotensive effects.