Alberta Health Services (AHS) has recently approved a formulary restriction on codeine which limits the use of codeine-containing products to adults (patients over the age of eighteen) within all AHS facilities.
While this restriction only applies to inpatient AHS facilities, there may be an impact upon community practitioners, as pediatric patients are discharged from hospital.
Morphine is the alternative opioid being recommended, as its effects will be more predictable and reliable than codeine.
Tips for community pharmacists
- If you have a large pediatric clientele or are located near a hospital or urgent care center, you may wish to regularly stock small quantities of morphine.
- Morphine must always be prescribed on a triplicate prescription.
- Morphine is dosed according to body weight in children. The initial dose AHS recommends in opioid naïve children is 0.2 mg/kg/dose and this may be given every 4 hours (as needed). Since morphine is titrated to effect, there is a fairly broad range of acceptable doses (dose range: 0.1-0.5 mg/kg/dose, reference: Pediatric Lexicomp), but generally starting doses will be on the lower side of this dosing range.
- Morphine is available both in liquid and immediate release oral tablet forms.
- Morphine liquid and tablets should be dispensed in containers with child-resistant lids.
- Always dispense morphine liquid with an appropriately sized oral syringe.
- Demonstrate how to withdraw liquid using the syringe and show the caregiver where the dose volume would be on the syringe. The dose volume could be marked on the oral syringe with a waterproof marker if that is helpful.
- Do not pre-draw oral syringes as there is no good way to store these securely in the home.
- Always remind parents to store the medications safely out of reach of children.
- Often, children will be prescribed ibuprofen and acetaminophen as well. As you know, these products are available ‘over the counter’ and may be given to children without families making you aware of this. You may wish to inquire if other pain medications have been suggested, to assist in choosing an appropriate product and to ensure appropriate understanding of dose and administration.
Why the restriction?
The impetus for this restriction stems from several published cases of respiratory depression and death in children when they were given codeine.
Codeine is a prodrug that is converted by Cytochrome P450 2D6 (CYP2D6) to morphine. Codeine must be metabolized to its active metabolite – morphine – for its therapeutic effect. The activity of the enzyme CYP2D6 is highly variable in patient populations. Approximately 8% of Canadians are “ultra-rapid” metabolizers of codeine and convert codeine to morphine more quickly and completely than the general population. These patients can attain toxic morphine plasma levels, despite receiving only therapeutic codeine doses. Conversely, 10% of the population is considered to be “poor” metabolizers, which means they are unable to convert codeine to morphine at all. As a consequence, these patients experience little pain relief from codeine.
Testing for the “ultra rapid” and “poor” codeine CYP2D6 genetic variants is not yet readily available. At the bedside, it is impossible to predict who might be affected, even if a thorough medication history is taken.
