BNF for Children 2011-2012

BNFC 2011–2012 4.7.2 Opioid analgesics 203Pregnancy Respiratory depression and withdrawalsymptoms can occur in the neonate if opioid analgesicsare used during delivery; also gastric stasis and inhalationpneumonia has been reported in the mother ifopioid analgesics are used during labour.Side-effects Opioid analgesics share many sideeffects,although qualitative and quantitative differencesexist. The most common side-effects include nauseaand vomiting (particularly in initial stages), constipation,dry mouth and biliary spasm; larger doses producemuscle rigidity, hypotension and respiratory depression(for reversal of opioid-induced respiratory depression,see section 15.1.7); neonates, particularly if preterm,may be more susceptible. Other common side-effectsof opioid analgesics include bradycardia, tachycardia,palpitation, oedema, postural hypotension, hallucinations,vertigo, euphoria, dysphoria, mood changes, dependence,dizziness, confusion, drowsiness, sleep disturbances,headache, sexual dysfunction, difficulty withmicturition, urinary retention, ureteric spasm, miosis,visual disturbances, sweating, flushing, rash, urticaria,and pruritus. Overdosage: see Emergency Treatment ofPoisoning, p. 28.Long-term use of opioid analgesics can lead to hypogonadismand adrenal insufficiency in both boys andgirls. This is thought to be dose related and can lead toamenorrhoea, reduced libido, infertility, depression, anderectile dysfunction. Long-term use of opioid analgesicshas also been associated with a state of abnormal painsensitivity (hyperalgesia). Pain associated with hyperalgesiais usually distinct from pain associated with diseaseprogression or breakthrough pain, and is oftenmore diffuse and less defined. Treatment of hyperalgesiainvolves reducing the dose of opioid medication orswitching therapy; cases of suspected hyperalgesiashould be referred to a specialist pain team.Interactions See Appendix 1 (opioid analgesics)(important: special hazard with pethidine and possiblyother opioids and MAOIs).Skilled tasks Drowsiness may affect performance ofskilled tasks (e.g. driving); effects of alcohol enhanced.Driving at the start of therapy with opioid analgesics,and following dose changes, should be avoided.Strong opioids Morphine remains the most valuableopioid analgesic for severe pain although it frequentlycauses nausea and vomiting. It is the standard againstwhich other opioid analgesics are compared. In additionto relief of pain, morphine also confers a state ofeuphoria and mental detachment.Morphine is the opioid of choice for the oral treatmentof severe pain in palliative care. It is given regularlyevery 4 hours (or every 12 or 24 hours as modifiedreleasepreparations). For guidelines on dosage adjustmentin palliative care, see p. 17.Buprenorphine has both opioid agonist and antagonistproperties and may precipitate withdrawal symptoms,including pain, in children dependent on other opioids.It has abuse potential and may itself cause dependence.It has a much longer duration of action than morphineand sublingually is an effective analgesic for 6 to 8hours. Unlike most opioid analgesics, the effects ofbuprenorphine are only partially reversed by naloxone.It is used rarely in children.Diamorphine (heroin) is a powerful opioid analgesic. Itmay cause less nausea and hypotension than morphine.In palliative care the greater solubility of diamorphineallows effective doses to be injected in smaller volumesand this is important in the emaciated child.Diamorphine is sometimes given by the intranasal routeto treat acute pain in children, for example, in accidentand emergency units; however, as yet, there is limitedsafety and efficacy data to support this practice.Alfentanil, fentanyl and remifentanil are used byinjection for intra-operative analgesia (section15.1.4.3). Fentanyl is available in a transdermal drugdelivery system as a self-adhesive patch which is changedevery 72 hours.Methadone is less sedating than morphine and acts forlonger periods. In prolonged use, methadone should notbe administered more often than twice daily to avoid therisk of accumulation and opioid overdosage. Methadonemay be used instead of morphine when excitation (orexacerbation of pain) occurs with morphine. Methadonemay also be used to treat children with neonatal abstinencesyndrome (section 4.10).Papaveretum should not be used in children; morphineis easier to prescribe and less prone to error with regardto the strength and dose.Pethidine produces prompt but short-lasting analgesia;it is less constipating than morphine, but even in highdoses is a less potent analgesic. Its use in children is notrecommended. Pethidine is used for analgesia in labour;however, other opioids, such as morphine or diamorphine,are often preferred for obstetric pain.Tramadol is used in older children and producesanalgesia by two mechanisms: an opioid effect and anenhancement of serotonergic and adrenergic pathways.It has fewer of the typical opioid side-effects (notably,less respiratory depression, less constipation and lessaddiction potential); psychiatric reactions have beenreported.Weak opioids Codeine is used for the relief of mild tomoderate pain but is too constipating for long-term use.Dihydrocodeine has an analgesic efficacy similar tothat of codeine; doses may be given every 4 hours.Dose Doses of opioids may need to be adjustedindividually according to the degree of analgesia andside-effects; response to opioids varies widely, particularlyin the neonatal period. Opioid overdosage can haveserious consequences and the dose should be calculatedand checked with care.Postoperative analgesia A combination of opioidand non-opioid analgesics is used to treat postoperativepain (section 15.1.4.2). The use of intra-operativeopioids affects the prescribing of postoperative analgesics.A postoperative opioid analgesic should be givenwith care since it may potentiate any residual respiratorydepression (for the treatment of opioid-inducedrespiratory depression, see section 15.1.7).Morphine is used most widely. Tramadol is not aseffective in severe pain as other opioid analgesics.Buprenorphine may antagonise the analgesic effect ofpreviously administered opioids and is generally notrecommended. Pethidine is unsuitable for post-operativepain because it is metabolised to norpethidinewhich may accumulate, particularly in neonates and inrenal impairment; norpethidine stimulates the centralnervous system and may cause convulsions.4 Central nervous system