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Morphine / Naltrexone Dosage

The information at is not a substitute for medical advice. ALWAYS consult your doctor or pharmacist.

Usual Adult Dose for:

Additional dosage information:

Usual Adult Dose for Pain

It is critical to adjust the dosing regimen for each patient individually, taking into account the patient's prior analgesic treatment experience. In selecting an initial dose, attention should be given to:
1) the total daily dose, potency, and kind of opioid the patient has been taking previously;
2) the reliability of the relative potency estimate used to calculate the equivalent dose of morphine needed;
3) the patient's degree of opioid experience and opioid tolerance;
4) the general condition and medical status of the patient;
5) concurrent medication(s);
6) the type and severity of the patient's pain.

The following dosing recommendations can be considered approaches to what is actually a series of clinical decisions over time in the management of the pain of an individual patient.

Care should be taken to use low initial doses in patients who are not already opioid tolerant, especially those who are receiving concurrent treatment with muscle relaxants, sedatives, or other CNS active medications. Patients may subsequently be titrated to a once a day or twice a day dosage which adequately maintains their pain.

Other oral morphine formulations may be converted to morphine-naltrexone by administering one-half of the patient's total daily oral morphine dose as morphine-naltrexone every 12 hours or by administering the total daily oral morphine dose as morphine-naltrexone once every 24 hours. Morphine-naltrexone should not be given more frequently than every 12 hours. It is better to underestimate the patient's 24 hour oral morphine requirement and provide rescue medication than to overestimate and manage an adverse event.

Morphine-naltrexone can be administered to patients previously receiving treatment with parenteral morphine or other opioids.
Parenteral to Oral Morphine Ratio:
It may take anywhere from 2 to 6 mg of oral morphine to provide analgesia equivalent to 1 mg of parenteral morphine. A dose of oral morphine three times the daily parenteral morphine requirement may be sufficient in chronic use settings.
Other Oral or Parenteral Opioids to Oral Morphine Sulfate:
There is a lack of systematic evidence available on these types of analgesic substitutions. Therefore, specific recommendations are not possible.

The first dose of morphine-naltrexone may be taken with the last dose of any immediate release (short acting) opioid medication due to the extended release characteristics of morphine-naltrexone.

Renal Dose Adjustments

In patients with end-stage renal disease start at the lower suggested dosage and the patient's needs, titrate dosage upwards slowly, and increase the dosage intervals to prevent accumulation of the metabolite morphine-6-glucoronide.

Naltrexone: Data not available

Liver Dose Adjustments

Morphine: Data not available

Naltrexone undergoes extensive hepatic metabolism and has the potential to cause further hepatic injury in patients with liver dysfunction. Therefore, the use of naltrexone is not recommended in patients with acute hepatitis or liver failure and should be used with caution in patients with active liver disease.


The 100 mg/4 mg capsules are for use only in opioid tolerant patients.

Safety and effectiveness have not been established in pediatric patients (less than 18 years of age).


A large percentage (50% to 100%) of a morphine dose is removed from circulation by hemodialysis.

Naltrexone: Data not available

Other Comments

Concurrent administration of high fat food decreases the rate and extent of morphine absorption. However, the total bioavailability is not affected. Coadministration of a high fat meal does not compromise sequestration of naloxone.

Morphine-naltrexone is to be swallowed whole or the contents of the capsules sprinkled on apple sauce and taken by mouth. The pellets in the capsules are not to be crushed, dissolved, or chewed before swallowing. Tampering with the formulation by crushing or chewing the pellets results in the rapid release and absorption of both morphine and naltrexone comparable to the oral solution.