Morphine

Drug Information: Morphine

Morphine is a potent opioid analgesic medication used to manage severe pain. Derived from the opium poppy, it is a Schedule II controlled substance due to its high potential for abuse and dependence. It works by binding to opioid receptors in the brain and spinal cord, effectively reducing the perception of pain. While highly effective, its use requires careful consideration of potential side effects and risks, and is typically reserved for situations where other pain relievers are inadequate.

Category

Analgesic

Mechanism of Action

Morphine exerts its analgesic effects by acting as an agonist at opioid receptors, primarily the mu (μ), kappa (κ), and delta (δ) opioid receptors, located throughout the central nervous system (CNS) and in the periphery. The primary analgesic effect is mediated through the activation of mu receptors. Activation of these receptors modulates pain pathways, reducing the transmission of pain signals from the periphery to the brain. Specifically, morphine binding leads to:

• Decreased neuronal excitability: Opioid receptor activation increases potassium conductance and decreases calcium conductance, leading to hyperpolarization and reduced neuronal firing.
• Inhibition of neurotransmitter release: Morphine inhibits the release of neurotransmitters such as substance P, glutamate, and acetylcholine from presynaptic terminals, further reducing pain signal transmission.
• Activation of descending inhibitory pathways: Morphine activates descending pain inhibitory pathways from the brainstem, which further modulate pain perception at the spinal cord level.

Beyond analgesia, the interaction with these receptors also accounts for other effects of morphine, including respiratory depression (primarily mu receptor-mediated), euphoria (primarily mu receptor-mediated), sedation, constipation, and physical dependence. The variability in individual responses to morphine is influenced by genetic factors affecting opioid receptor expression and function, as well as individual pain thresholds and psychological factors.

Clinical Uses

Morphine is primarily used for the management of severe pain, especially:

• Post-operative pain: It is frequently administered following surgical procedures to alleviate intense pain.
• Cancer pain: Morphine is a mainstay in the management of chronic pain associated with cancer, improving quality of life for patients.
• Acute pain from trauma: It is used to treat severe pain resulting from injuries, burns, or other traumatic events.
• Myocardial infarction (MI): Morphine is sometimes used in the initial management of MI to relieve pain and reduce anxiety.
• Pulmonary edema: Morphine can reduce preload and afterload in patients with acute pulmonary edema, improving breathing.

It’s crucial to use morphine judiciously, considering the potential for addiction and adverse effects. Alternative pain management strategies should be explored whenever possible, and patients should be closely monitored during morphine therapy.

Dosage

Dosage varies significantly depending on the individual, the severity of pain, and the route of administration. Here are some general guidelines:

• Adults:
  • Oral: 10-30 mg every 4 hours as needed. Sustained-release formulations are available for longer-lasting pain relief (e.g., 15-30 mg every 8-12 hours).
  • Intravenous (IV): 2.5-10 mg every 3-4 hours as needed.
  • Intramuscular (IM) or Subcutaneous (SC): 5-20 mg every 3-4 hours as needed.
  • Epidural: 2-10 mg (single dose) or continuous infusion.
• Pediatrics: (Use with extreme caution and only under close medical supervision)
  • Oral: 0.2-0.5 mg/kg every 4 hours as needed.
  • IV/IM/SC: 0.05-0.2 mg/kg every 3-4 hours as needed.

Dosage should be individualized and titrated to effect, with careful monitoring for respiratory depression and other adverse effects. Lower doses are generally recommended for elderly or debilitated patients.

Indications

Common indications for Morphine include:

• Severe acute pain
• Chronic pain management (e.g., cancer pain)
• Post-operative pain
• Pain associated with myocardial infarction
• Pain management in palliative care

Contraindications

Contraindications for Morphine include:

• Significant respiratory depression
• Acute or severe bronchial asthma in an unmonitored setting or in the absence of resuscitative equipment
• Known hypersensitivity to morphine or other opioids
• Paralytic ileus
• Delayed gastric emptying
• Concomitant use with monoamine oxidase inhibitors (MAOIs) or within 14 days of stopping MAOIs
• Head injury or increased intracranial pressure
• Severe liver or kidney impairment

FAQ

• Q: What are the common side effects of Morphine?
  A: Common side effects include constipation, nausea, vomiting, drowsiness, dizziness, itching, and respiratory depression.
• Q: Can Morphine cause addiction?
  A: Yes, Morphine has a high potential for addiction and physical dependence. Prolonged use can lead to tolerance, requiring higher doses to achieve the same effect.
• Q: What should I do if I miss a dose of Morphine?
  A: Take the missed dose as soon as you remember. However, if it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not double the dose to catch up.
• Q: Can I drink alcohol while taking Morphine?
  A: No, alcohol should be avoided while taking Morphine as it can significantly increase the risk of respiratory depression and other side effects.
• Q: Does Morphine interact with other medications?
  A: Yes, Morphine can interact with several medications, including other opioids, benzodiazepines, muscle relaxants, and certain antidepressants (MAOIs). Inform your doctor about all medications you are taking before starting Morphine.
• Q: How is Morphine administered?
  A: Morphine can be administered orally (tablets, capsules, or liquid), intravenously (IV), intramuscularly (IM), subcutaneously (SC), or epidurally.
• Q: What are the signs of a Morphine overdose?
  A: Signs of a Morphine overdose include slowed or stopped breathing, pinpoint pupils, severe drowsiness or loss of consciousness, and clammy skin. If you suspect an overdose, seek immediate medical attention.
• Q: How should Morphine be stored?
  A: Morphine should be stored in a secure location, out of reach of children and pets, and at room temperature, away from moisture and heat.