Morphine/naltrexone

Morphine/naltrexone is a combination drug used in the management of chronic pain. It contains morphine, a powerful opioid analgesic, and naltrexone, an opioid antagonist. The purpose of the combination is to provide effective pain relief (from the morphine) while reducing the potential for misuse (through the inclusion of naltrexone).

Composition

The drug is composed of two active ingredients: morphine sulfate, an opioid analgesic, and naltrexone hydrochloride, an opioid antagonist. Morphine sulfate is responsible for the drug's pain-relieving effects, while naltrexone hydrochloride is intended to deter abuse of the drug.

Mechanism of Action

Morphine works by binding to mu-opioid receptors in the brain, spinal cord, and other areas of the body. This binding action reduces the perception of pain. Naltrexone, on the other hand, is an opioid antagonist. It works by binding to opioid receptors without activating them, effectively blocking the effects of opioids like morphine. In the case of morphine/naltrexone, the naltrexone is intended to remain sequestered and not released under normal conditions. However, if the drug is tampered with (for example, by crushing or dissolving for injection), the naltrexone is released and can block the effects of the morphine.

Indications

Morphine/naltrexone is indicated for the management of pain severe enough to require daily, around-the-clock, long-term opioid treatment and for which alternative treatment options are inadequate.

Side Effects

Common side effects of morphine/naltrexone include constipation, nausea, sleepiness, vomiting, tiredness, headache, dizziness, abdominal pain. Serious side effects may include addiction, abuse, and misuse, life-threatening respiratory depression, neonatal opioid withdrawal syndrome, and risks from concomitant use with benzodiazepines or other CNS depressants.

Contraindications

Morphine/naltrexone is contraindicated in patients with significant respiratory depression, acute or severe bronchial asthma in an unmonitored setting or in the absence of resuscitative equipment, known or suspected gastrointestinal obstruction, and hypersensitivity to morphine or naltrexone.

See Also

• Opioid
• Opioid antagonist
• Morphine
• Naltrexone