Use in palliative care
Opioid use at different ages
Opioid use in pregnancy, neonates and infants
Opioid use in neonates and infants should be initiated and managed by specialists.
Although there is extensive knowledge about pain treatment during labour, there has been little discussion concerning the treatment of pain during pregnancy. Only a few case studies have been published, in which opioids, non-steroidal anti-inflammatory drugs (NSAIDs), antidepressants, mu opioid receptor agonists, and anticonvulsants were used in the treatment of pain.
None of the currently prescribed pain medications and adjuvant drugs are categorically proven to be safe for the developing foetus. The main role of animal studies is to understand the mechanisms of teratogenicity, but they cannot always predict whether a drug will be teratogenic in humans.
Opioid use in children
Opioid use in children should be initiated and managed by specialists.
When treating pain in infants, it is important to understand that, although most of the major organ systems are anatomically well developed at birth, their functional maturity is often delayed.
There are several factors to consider in assessing pain:1
- the pain itself (child’s opinion, parent and staff observations, body sites, severity, times of pain, nature of the pain, precipitating and relieving factors);
- coping skills of the child and family;
- past experience of the child and family;
- anxiety and emotional distress levels in the child and family;
- meaning of the pain and underlying disease to the child and family.
Between 2 and 6 years of age, children may not have any logical explanation for pain or other symptoms. They may not understand or appreciate any type of intervention, especially those that are painful. Children between the ages of 7 and 10 years exhibit concrete-logical thinking, although they may remain confused about internal organs and functions, as well as other relationships.
Typically, children who are 8 years or older are capable of understanding numerical scales and word descriptors.
The World Institute of Pain discusses a best practice approach to pain management in children which includes:2
- Self Report, which is the golden standard to obtain, if possible.
- Behavioural methods, including neonatal facial coding, isolation, sleep and activity measures.
- Biological methods for vital signs and stress hormone measurement.
The paediatric population is at risk of inadequate pain management, with age-related factors affecting pain management in children. Children are often given minimal or no analgesia for procedures that would routinely be treated aggressively in adults. Although much is not known about pain management in children, it has not been widely or effectively translated into routine clinical practice.
Misconceptions that can lead to under treatment of pain in children3
- The myth that infants and children do not feel pain, or suffer less from it than adults.
- Lack of routine pain assessment in children.
- Lack of knowledge regarding newer modalities and proper dosing strategies for the use of analgesics in children.
- Fears of respiratory depression or other adverse effects of analgesic medications.
- The belief that preventing pain in children takes too much time and effort.
Most analgesics (including opioids and local anaesthetics) are conjugated in the liver.4 Newborns, and especially premature infants, have delayed maturation of the enzyme systems involved in drug conjugation, including sulphation, glucuronidation, and oxidation. Several of these hepatic enzyme systems, including cytochrome P450 subtypes, and the mixed-function oxidases, mature at varying rates over the first 1 to 6 months of life.5
Newborns, and especially premature infants, have diminished ventilatory responses to hypoxaemia and hypercarbia.6, 7 These ventilatory responses can be further impaired by CNS depressant drugs such as opioids and benzodiazepines.
Opioid use in older patients
Opioid medications are often under-used in the elderly.8 In a study of 4003 patients with cancer pain, those over 85 years were more likely to receive no analgesia.8 However, general opinion is that appropriate use of opioids can lead to significant improvement in the quality of life of elderly patients suffering from chronic pain.8
It should be remembered that renal function will naturally deteriorate with age, and hence the ability of older patients to handle renally excreted, active, opioid metabolites, such as morphine-6-glucuronide, can be expected to be reduced. In addition, as a result of other changes in physiology, elderly patients are also likely to suffer from some degree of hepatic impairment, decreased absorption, higher peak concentration and changes in lean body mass, which will result in a slower decline in the concentration-time curve.8
The elderly are also at greater risk of side effects, such as respiratory depression, due to drug accumulation (as a result of any concomitant heart or liver disease) and drug-drug interactions. This patient group also tend to be more susceptible to the effects of opioids as a result of neurochemical changes in the ageing brain.8 Opioids can affect cognition and psychomotor function, which can be potentially hazardous in this age group.8 This is especially true when doses are initiated or changed.8 Evidence also suggests that patients with a history of dementia are at greater risk from developing confusion.8
Every effort should be made to keep side effects to a minimum, some will resolve as the patient develops tolerance and others can be treated with concomitant medicaton, but when this is not the case, dose reduction accompanied by additional, non-opioid, analgesic adjuvant therapy may prove beneficial.8
It is also important to allay any patient fears about addiction or concerns about the inability to stop the medication.8
Opioid medication has been shown to be a very useful tool in the treatment of pain in the elderly.8 However, as with all patients, individual patient response to opioids can vary widely9 and it is therefore important to treat patients on an individualised basis, titrating dose to patient response, whilst taking into account the risk of side effects.
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References
1) Faull C, Carter Y, Woof R (Eds.) Handbook of Palliative Care. p.262.
2) Bever JE, Wells N: The assessment of pain in children. Pediatr Clin North Am 1989; 36:837-854.
3) Committee on Psychosocial Aspects of Child and Family Health, American Academy of Pediatrics; Task Force on Pain in Infants, Children, and Adolescents, American Pain Society. The assessment and management of acute pain in infants, children, and adolescents. Pediatrics . 2001; 108(3):793-797.
4) http:/anti-infectives/Paris-Event/Live-Webcast.cfmwww.ama-cmeonline.com/pain_mgmt/module06/06phar/.
5) Tateishi T, Nakura H, Asoh M, et al. A comparison of hepatic cytochrome P450 protein expression between infancy and postinfancy. Life Sci . 1997; 61:2567-2574.
6) Martin RJ, DiFiore JM, Jana L, et al. Persistence of the biphasic ventilatory response to hypoxia in preterm infants. J Pediatr . 1998; 132:960-964.
7) Cohen G, Malcolm G, Henderson-Smart D. Ventilatory response of the newborn infant to mild hypoxia. Pediatr Pulmonol. 1997; 24:163-172.
8) Caracci G. The Use of Opioid Analgesics in the Elderly. Clinical Geriatrics. Vol 11; 18-21.
9) British National Formulary. Available from: URL: http:/anti-infectives/Paris-Event/Live-Webcast.cfmwww.bnf.org/bnf/.