Mst® Continus® (Morphine Sulfate)

Morphine sulfate is an opioid analgesic used to treat pain conditions that involve the central nervous system.

• Acute postoperative pain: provides rapid relief of severe pain following surgery.
• Cancer‑related pain: controls persistent pain associated with malignant disease.
• Chronic severe non‑cancer pain: manages long‑term severe pain when other therapies are inadequate.

• Morphine sulfate acts as a full agonist at μ‑opioid receptors in the central nervous system. Binding to these G‑protein‑coupled receptors inhibits adenylate cyclase activity, reduces calcium influx and increases potassium efflux, leading to hyperpolarization of neurons. This suppresses the transmission of nociceptive signals and alters the perception of pain, while also producing sedation and euphoria. The effect is dose‑dependent and reversible upon discontinuation.

Morphine sulfate may cause a range of adverse reactions, varying from mild to life‑threatening.

Common Side Effects

• Nausea: feeling of sickness that may lead to vomiting.
• Constipation: reduced bowel movements and hard stools.
• Drowsiness: increased sleepiness or fatigue.
• Dry mouth: reduced salivation causing throat discomfort.

Serious or Rare Side Effects

• Respiratory depression: slowed or shallow breathing that can be fatal.
• Severe hypotension: marked drop in blood pressure leading to dizziness or fainting.
• Anaphylactic reaction: sudden allergic response with rash, swelling, and airway compromise.

When prescribing morphine sulfate, clinicians should observe several safety measures to minimize risk.

• Assess pain severity: confirm that opioid therapy is appropriate for the patient’s pain level.
• Evaluate organ function: check hepatic and renal function before initiating therapy.
• Monitor respiratory status: observe for signs of respiratory depression, especially after dose adjustments.
• Avoid abrupt discontinuation: taper the dose gradually to prevent withdrawal symptoms.
• Use caution in the elderly: start with lower doses and monitor for increased sensitivity.
• Store at ambient temperature: keep in the original container, protect from moisture and heat.

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

Major Interactions (Avoid)

• Central nervous system depressants (e.g., benzodiazepines, alcohol): may cause profound sedation and respiratory depression.
• Monoamine oxidase inhibitors (MAOIs): increase risk of severe hypertension or serotonin syndrome.
• Strong CYP3A4 inhibitors (e.g., ketoconazole, itraconazole): raise morphine plasma concentrations, enhancing toxicity.

Moderate Interactions (Monitor Closely)

• CYP3A4 inducers (e.g., rifampin, carbamazepine): may reduce morphine levels, decreasing analgesic effect.
• Selective serotonin reuptake inhibitors (SSRIs) or serotonin‑norepinephrine reuptake inhibitors (SNRIs): can increase the risk of serotonin syndrome.