The response rate was worse in dental procedures than <strong>with</strong>other surgical procedures. Codeine performed unfavourablycompared <strong>with</strong> simple analgesics such as paracetamol andNSAIDs. 5 When combined <strong>with</strong> paracetamol, <strong>codeine</strong> appearedmore clinically useful. However, the additional effect of <strong>codeine</strong>,compared <strong>with</strong> the same dose of paracetamol alone, wasmodest, <strong>with</strong> a further 10–15% of patients achieving adequateanalgesia. 6 A meta-analysis of opioids for osteoarthritis of theknee or hip found that the modest benefits of <strong>codeine</strong> wereoutweighed by adverse events. 7Many of the preparations available in Australia contain less<strong>codeine</strong> than the doses studied in most clinical trials (generally60 mg <strong>codeine</strong>). It is questionable if these low-dose <strong>codeine</strong>combination products (containing 8–15 mg <strong>codeine</strong> per tablet)provide meaningful analgesia over simple non-opioid analgesicsalone. 8Adverse effectsThe common adverse effects of <strong>codeine</strong>, which include nausea,vomiting, constipation, drowsiness and dizziness, becomemore likely <strong>with</strong> higher or repeated doses. Constipation can beparticularly problematic <strong>with</strong> larger doses and <strong>codeine</strong> is bestavoided after bowel surgery. Medication overuse headachesare a concern in people using <strong>codeine</strong>-containing medicationsregularly (more than 10 days per month). While the risk ofdeveloping medication overuse headache <strong>with</strong> <strong>codeine</strong> isunknown (given multiple confounding factors in observationalstudies), combination analgesics and opioids (such as <strong>codeine</strong>)are likely to have a significantly higher risk than simple analgesicssuch as paracetamol or NSAIDs. 9,10 Less well appreciated, butseen in some epidemiological studies, is the small but significantrisk of falls, fractures and even motor vehicle accidents. 11-13At higher doses, or in ultrafast metabolisers, life-threateningrespiratory depression can occur especially when <strong>codeine</strong> iscombined <strong>with</strong> other respiratory depressant drugs, such asbenzodiazepines.BreastfeedingAttention was raised to the potential harms of <strong>codeine</strong> duringbreastfeeding after the death of a neonate whose mother hadbeen prescribed <strong>codeine</strong> postpartum. Very high concentrationsof morphine in the deceased baby's blood were attributed tothe mother being a CYP2D6 ultrafast metaboliser. 14,15 The USFood and Drug Administration issued a letter outlining theneed for caution and close monitoring if prescribing <strong>codeine</strong> tobreastfeeding women. 15 The <strong>Australian</strong> Medicines Handbookadvises avoiding <strong>codeine</strong> in breastfeeding women. 16ChildrenDue to their developing physiology and body composition,infants and young children have an increased susceptibilityto the adverse effects of opioids. Pharmacogenetic variantswere identified as a causal factor in the death and anoxic braininjury of two young children given <strong>codeine</strong> for analgesia aftertonsillectomy. Several countries have set minimum ages for<strong>codeine</strong> use, however the age they set varies considerablygiven the lack of clarity as to when the risk diminishes. 1Some children's hospitals have removed <strong>codeine</strong> from theirformularies. 1 The UK Medicines and Healthcare ProductsRegulatory Agency advises that <strong>codeine</strong>-containing preparationsfor cough should not be used by people less than 18 years old,as the risks outweigh the benefits. 17ElderlyOlder people have an increased susceptibility to opioids. Theymay also be taking interacting drugs. Pharmacogenetic variabilitycan have a considerable impact on adverse effects such assedation, confusion, falls and injury. While combination productscontaining <strong>codeine</strong> are often considered safe, a cohort studyfound the risk of injury was higher in older people using theseproducts than in those taking other opioids or sedating drugs. 13Drug dependence and <strong>codeine</strong> abuseAlthough considered a weak opioid, <strong>codeine</strong>, like all opioids, isassociated <strong>with</strong> the problems of tolerance and drug dependence<strong>with</strong> long-term use. Codeine abuse is also of concernparticularly <strong>with</strong> combination products, as it frequently results inexposure to supratherapeutic doses of paracetamol or NSAIDs.Deaths and serious morbidity, such as liver toxicity and gastrichaemorrhage, have been reported. 18Access to <strong>codeine</strong> <strong>with</strong>in Australia is inconsistent. Codeine 30 mgtablets are classified Schedule 8 (drugs <strong>with</strong> potential for abuse oraddiction), whereas the same dose combined <strong>with</strong> paracetamol isclassified Schedule 4 (drugs available <strong>with</strong> prescription). A largenumber of lower-dose combination preparations are available<strong>with</strong>out prescription. Codeine dependence and subsequent abusehas been reported to occur in people who had initially usedover-the-counter products for painful conditions. 18ConclusionCodeine's use as an analgesic is confounded by variablepharmacokinetics that make its efficacy and safety difficult topredict in an individual.The limited efficacy seen in clinical trials, even at higher doses,is disappointing and raises questions as to the value of thelow-dose combination preparations available in Australia. Inmany instances where a combination containing <strong>codeine</strong> hasbeen prescribed, treatment <strong>with</strong> paracetamol or an NSAID mayhave been just as effective. In cases where there is a genuineneed for stronger analgesia, treatment <strong>with</strong> a low dose of theactive metabolite morphine (or one of the synthetic alternatives)provides a more predictable response.While <strong>codeine</strong>'s adverse effects are generally troublesomerather than serious, there are reports of serious adverse eventsand fatalities. The potential for drug dependence and misuse,resulting in toxicity from the paracetamol or NSAIDs used134 | Volume 34 | NUMBER 5 | OCTOBER 2011 www.australianprescriber.com
in combination products, also raises concerns regarding theavailability of <strong>codeine</strong> in the community. As <strong>with</strong> any medicine,due care should be taken in recommending or prescribing thisdrug. In other words, take caution <strong>with</strong> <strong>codeine</strong>.References1. MacDonald N, MacLeod SM. Has the time come to phaseout <strong>codeine</strong>? Can Med Assoc J 2010;182:1825.2. Analgesic: Getting to know your drugs [2007]. In: eTGcomplete [Internet]. Melbourne: Therapeutic Guidelines;2010.3. Miks G, Trausch B, Rodewald C, Hofmann U, Richter K,Gramatte T, et al. Effect of <strong>codeine</strong> on gastrointestinalmotility in relation to CYP2D6 phenotype.Clin Pharmacol Ther 1997;61:459-66.4. Zhou S. Polymorphism of human cytochrome P450 2D6and its clinical significance. Part 1. Clin Pharmacokinet2009;48:689-723.5. Derry SM. Single dose <strong>codeine</strong>, as a single agent, for acutepostoperative pain in adults. Cochrane Database Syst Rev2010;14:CD008099.6. Toms L, Derry S, Moore RA, McQuay HJ. Single doseoral paracetamol (acetaminophen) <strong>with</strong> <strong>codeine</strong> forpostoperative pain in adults. Cochrane Database Syst Rev2009;21:CD001547.7. Nuesch ER, Rutjes AW, Husni E, Welch V, Juni P. Oral ortransdermal opioids for osteoarthritis of the knee or hip.Cochrane Database Syst Rev 2009;7:CD003115.8. Murnion BP. Combination analgesics in adults. Aust Prescr2010;33:113-5.9. Williams D. Medication overuse headache. Aust Prescr2005;28:143-5.10. Headache Classification Committee, Olesen J, Bousser MG,Diener HC, Dodick D, First M, et al. New appendix criteriaopen for a broader concept of chronic migraine. Cephalalgia2006;26:742-6.11. Vestergaard P, Rejnmark L, Mosekilde L. Fracture riskassociated <strong>with</strong> the use of morphine and opiates.J Intern Med 2006;260:76-87.12. Bachs LC, Engeland A, Morland JG, Skirtveit S. The risk ofmotor vehicle accidents involving drivers <strong>with</strong> prescriptionsof <strong>codeine</strong> or tramadol. Clin Pharmacol Ther 2009;85:596-9.13. Buckeridge D, Huang A, Hanley J, Kelome A, Reidel K,Verma A, et al. Risk of injury associated <strong>with</strong> opioid use inolder adults. J Am Geriatr Soc 2010;58:1664-70.14. Kennedy D. Analgesics and pain relief in pregnancy andbreastfeeding. Aust Prescr 2011;34:8-10.15. Use of <strong>codeine</strong> products in nursing mothers – questions andanswers. 2007. US Food and Drug Administration.www.fda.gov/Drugs/DrugSafety/PostmarketDrugSafetyInformationforPatientsandProviders/ucm118113.htm [cited 2011 Sep 9]16. <strong>Australian</strong> Medicines Handbook. Codeine – Analgesics. In:<strong>Australian</strong> Medicines Handbook. Adelaide: AMH Pty Ltd;2011. p. 50-1.17. Medicines and Healthcare Products Regulatory Agency. Oralliquid cough medicines containing <strong>codeine</strong> should not beused in children and young people under 18 years. 2010.www.mhra.gov.uk [cited 2011 Sep 9]18. Frei MY, Neilsen S, Dobbin MD, Tobin CL. Serious morbidityassociated <strong>with</strong> misuse of over-the-counter <strong>codeine</strong>ibuprofenanalgesics: a series of 27 cases. Med J Aust2010;193:294-6.Conflict of interest: none declaredSelf-test questionsThe following statements are either true or false(answers on page 159)3. Patients who are ultrafast metabolisers of <strong>codeine</strong> needhigher doses to obtain satisfactory analgesia.4. The dose of <strong>codeine</strong> found in over-the-counterproducts is too low to cause drug dependence.Dental notesPrepared by Michael McCullough, Chair,Therapeutics Committee, <strong>Australian</strong> DentalAssociation<strong>Cautions</strong> <strong>with</strong> <strong>codeine</strong>Patients who present <strong>with</strong> profound dental pain often do notrequire prescribed analgesics if they are treated promptlyby a dentist. In the vast majority of presentations, the dentaltreatment will manage the patients' pain. Nevertheless,although the prescription of an analgesic for ongoing painmanagement is often not required, professional advice aboutthe most appropriate and effective over-the-counter medicine touse is a professional courtesy we should offer to our patients.The considerable inter-individual variation in the effectivenessof <strong>codeine</strong>, combined <strong>with</strong> its rare but potentially seriousadverse events, suggests that <strong>codeine</strong> for dental pain should beavoided. Patients <strong>with</strong> ongoing pain who are able to use anon-steroidal anti-inflammatory drug, such as ibuprofen, arelikely to have more predictable control of their pain. The painmanagement strategies outlined in Therapeutic Guidelines: Oraland dental 1 provide clear advice to help patients manage theirpain or their expected pain, following dental treatment.The warning 'take caution <strong>with</strong> <strong>codeine</strong>' should resound inthe dental setting, particularly <strong>with</strong> patients who specificallyrequest opioid drugs as an alternative to adequate dentaltreatment.Reference1. Oral and Dental Expert Group. Dental management ofpatients taking medications. In: Therapeutic guidelines: oraland dental. Version 1. Melbourne: Therapeutic GuidelinesLimited; 2007. p.62.www.australianprescriber.com| Volume 34 | NUMBER 5 | OCTOBER 2011 135