Where data were available, more than half of codeine-related deaths involved people who were prescribed codeine.1 However 40% of people had used over-the- counter products and this suggests a serious issue for clinical practice that involves both prescribers and pharmacists.1
The numbers of patients who died from intentional overdose in this study suggests that prescribers should consider screening for depression and suicide risk prior to prescribing codeine. The high prevalence of substance use problems in patients who died from accidental overdose suggests that prescribers need to consider the risk of substance misuse before prescribing codeine, as is recommended for prescribing Schedule 8 substances.2
Prescribers need to be aware that codeine metabolism is dependent on the activity of cytochrome P450 2D6. Genetic variation in this enzyme produces some individuals (about 1%–2% of the white population) who are classed as ultrarapid metabolisers and have a greater risk of adverse events such as respiratory depression and fatal overdose due to the greater conversion of codeine to morphine.1,3 Conversely, poor metabolisers (about 5%–10% of the white population) have little codeine converted to morphine and therefore receive little analgesic benefit.1,3
Patient education is essential whether codeine is prescribed or dispensed over the counter. Pharmacists play a key role ensuring patients understand the potential dangers of codeine, particularly when taken in combination with other medicines (ie, benzodiazepines or opioids). Patients also need to understand the harms associated with combination products, such as paracetamol–codeine combinations or cold and flu medicines.