Morphine is a pure opioid agonist that produces analgesia by interacting with opioid receptors in the CNS, perhaps mimicking enkephalins and endorphins. It is relatively selective for the mu receptor, although it can interact with other opioid receptors at higher doses. In addition to analgesia, morphine also produces drowsiness, changes in mood, respiratory depression, decreased GI motility, nausea, vomiting, anxiolysis, euphoria, feelings of relaxation, and alterations of the endocrine and autonomic nervous system.
Extended-release morphine has demonstrated efficacy in the once-daily treatment of patients with chronic moderate to severe pain in several controlled and open-label clinical studies. Comparative studies with other long-acting analgesic preparations are not available.
|Oral bioavailability||Less than 40%|
|Protein binding||20% to 35%|
|AUC||273 ng/ml X hr|
|Volume of distribution||1 to 6 L/kg|
|Metabolism||Conjugation and demethylation in liver|
Patients with hypersensitivity to morphine or any product components
Patients with respiratory depression in the absence of resuscitative equipment
Patients with acute or severe bronchial asthma
Capsules and beads should be swallowed whole and must not be chewed, crushed, or dissolved.
Maximum daily dose should not exceed 1,600 mg.
Morphine can be abused, misused, or diverted.
Morphine can have additive effects when used with alcohol, other opioids, or illicit drugs that cause CNS depression.
Morphine may cause respiratory depression.
Respiratory depressant effects may be markedly exaggerated in the presence of head injury, other intracranial lesions, or a preexisting increase in intracranial pressure.
Morphine may cause severe hypotension.
Administer with caution to patients in circulatory shock.
Should not be given to patients with GI obstruction.
The most common (>10%) adverse effects were constipation, nausea, somnolence, vomiting, and headache.
Less common (5%-10%) adverse effects included peripheral edema, diarrhea, abdominal pain, infection, urinary tract infection, accidental injury, flu syndrome, back pain, rash, fever, insomnia, depression, paresthesia, anorexia, dry mouth, asthenia, and dyspnea.
Initial dose: 30 mg/day for patients who are not opioid-tolerant
Usual dose: Dosage is individualized
Maximum dose: 1,600 mg/day
Morphine sulfate extended-release capsules are a once-daily dosage form that has demonstrated safety and efficacy in the treatment of patients with chronic, moderate to severe pain who require around-the-clock therapy for an extended period. The product has a dual-release formulation that contains immediate- and sustained-release morphine beads. Once steady-state plasma levels are achieved (two to three days), the immediate-release beads provide rapid exposure to morphine while the sustained-release beads enable morphine to be absorbed by the body gradually, maintaining plasma morphine levels over a 24-hour dosing period. A potential advantage over other extended-release products is that Avinza capsules can be opened and sprinkled on food. The extended-release capsules provide a convenient, once- daily administration option for patients, but clinical comparisons to other long-acting analgesics, including additional morphine preparations, are not available.
Published June 2002. Content based on medical literature and product information available at that time.
P&T Portfolio--Avinza. Drug Topics 2002;14:HSE20.