Oramorph SR Dosage
Generic name: morphine sulfate
Dosage form: sustained release tablets
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NOTE: ORAMORPH SR TABLET MUST BE SWALLOWED WHOLE. DO NOT BREAK THE TABLET IN HALF. DO NOT CRUSH OR CHEW. TAKING BROKEN, CHEWED OR CRUSHED TABLETS COULD LEAD TO THE RAPID RELEASE AND ABSORPTION OF A POTENTIALLY TOXIC DOSE OF MORPHINE.
ORAMORPH SR is intended for use in patients who require more than several days of continuous treatment with a potent opioid analgesic. The sustained release nature of the formulation allows it to be administered on a more convenient schedule than conventional immediate-release oral morphine products (see CLINICAL PHARMACOLOGY - PHARMACOKINETICS). However, ORAMORPH SR does not release morphine continuously over the course of a dosing interval. The administration of single doses of ORAMORPH SR on a q12h dosing schedule will result in peak and trough plasma levels similar to those following an identical daily dose of morphine administered using conventional oral formulations on a q4h regimen. If pain is not controlled for a full 12 hours, then the dosing interval should be shortened, but to no less than 8 hours.
As with any potent opioid, it is critical to adjust the dosing regimen for each patient individually, taking into account the patient's prior analgesic treatment experience. Attention should be given to the following in determining the initial dose of ORAMORPH SR, (1) the daily dose, potency and characteristics of a pure agonist, or mixed agonist-antagonist, the patient has been taking previously, (2) the reliability of the relative potency estimate to calculate the dose of morphine needed [N.B.: potency estimates may vary with the route of administration], (3) the fact that roughly only 40% of the morphine sulfate in ORAMORPH SR becomes available after pre-systemic metabolization in the intestinal wall and the liver, (4) the degree of opioid tolerance, and (5) the general condition and medical status of the patient.
The following dosing recommendations for ORAMORPH SR, therefore, can only be considered suggested approaches to the series of clinical decisions in the management of pain of an individual patient.
Conversion from Conventional Immediate-Release Oral Morphine to ORAMORPH SR:
A patient's daily morphine requirement is established by using the Daily Oral Morphine Requirement of the immediate-release formulation which gives the Daily Oral Morphine Requirement for ORAMORPH SR. Since ORAMORPH SR is given on an 'every 12 hour' schedule, the single dose of ORAMORPH SR is half of the Daily Oral Morphine Requirement. Dose and dosing interval is adjusted as needed (see discussion below). For initial conversion, the 30 mg tablet strength is recommended for patients with a daily morphine requirement of 120 mg or less.
Conversion from Parenteral Morphine or Other Opioid Analgesics (parenteral or oral) to ORAMORPH SR:
Because of uncertainty about relative estimates of opioid potency and cross tolerance, as well as intersubject variation, initial dosing regimens should be conservative, i.e., an underestimation of the 24-hour oral morphine requirement is preferred to an overestimate. To this end, initial individual doses of ORAMORPH SR should be estimated conservatively. In patients whose daily morphine requirements are expected to be less than or equal to 120 mg per day, the 30 mg tablet strength is recommended for the initial titration period. Once a stable dose regimen is reached, the patient can be converted to the 60 mg or 100 mg tablet strength, as appropriate.
Estimates of the relative potency of opioids are only approximate, and are influenced by route of administration, individual patient differences, and possibly, by the patient's medical condition. Consequently, it is difficult to recommend any precise rule for converting a patient to ORAMORPH SR directly. However, the following general points should be considered:
- Parenteral to oral morphine ratio: Estimates of the oral-to-parenteral potency of morphine vary. Some authorities suggest that a dose of morphine only 3 times the daily parenteral morphine requirement may be sufficient in chronic use settings. (3 times the Daily Parenteral Morphine Requirement = the Daily Oral Morphine Requirement)
- Other parenteral or oral opioids to oral morphine: Because of a lack of reliable relative potency assays, specific recommendations are not possible. In general, it is safer to underestimate the Total Daily Dose of ORAMORPH SR required and rely upon ad hoc supplementation to deal with inadequate analgesia (see discussion which follows).
Use of ORAMORPH SR as the First Opioid Analgesic:
There has been no systematic evaluation of ORAMORPH SR as an initial opioid analgesic in the management of pain. Because it may be more difficult to titrate a patient using a sustained release morphine, it is ordinarily advisable to begin treatment using an immediate release formulation.
Considerations in the Adjustment of Dosing Regimens:
Whatever the approach, if signs of excessive opioid effects are observed early in a dosing interval, the next dose should be reduced. If this adjustment leads to inadequate analgesia, i.e., 'breakthrough' pain occurs late in the dosing interval, the dosing interval may be shortened. Alternatively, a supplemental dose of a short-acting analgesic may be given.
As experience is gained, adjustments can be made to obtain an appropriate balance between pain relief, opioid side effects and the convenience of the dosing schedule.
In adjusting dose requirements, it is recommended that the dosing interval never be extended beyond 12 hours, because the administration of very large single doses of ORAMORPH SR may lead to acute overdosage.
For patients with low daily morphine requirements, the 15 mg tablet should be used. In this regard, adjustment in dose should NOT be attempted by breaking or crushing the tablets. ORAMORPH SR tablets are intended to be swallowed whole.
Conversion from ORAMORPH SR to Parenteral Opioids:
When converting a patient from ORAMORPH SR to parenteral opioids, it is best to assume that the parenteral to oral potency relationship is high. NOTE THAT THIS IS THE CONVERSE OF THE STRATEGY USED WHEN THE DIRECTION OF CONVERSION IS FROM THE PARENTERAL TO ORAL FORMULATIONS. IN BOTH CASES, HOWEVER, THE AIM IS TO ESTIMATE THE NEW DOSE CONSERVATIVELY. For example, to estimate the required 24-hour dose of morphine for IM use, one could employ a conversion of 1 mg of morphine IM for every 6 mg of morphine as ORAMORPH SR. Of course, the IM 24-hour dose would have to be divided by six and administered on a q4h regimen. This approach is recommended because it is least likely to cause overdosage.