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Alcohol and benzodiazepines
There is no cross‐tolerance between opioids and alcohol or benzodiazepines and there is
therefore no pharmacological reason to use higher than ‘standard’ initial opioid doses in
patients with an alcohol or benzodiazepine addiction.
Alcohol and/or benzodiazepine abuse is relatively common and prevention of withdrawal
should be a clinical priority in all patients. If benzodiazepines are administered for the
treatment of withdrawal signs and symptoms, patient sedation levels must be monitored,
especially if they are receiving concurrent opioids. Excessive sedation will limit the amount
of opioid than can safely be given.
Cannabinoids
Evidence supporting the effectiveness of cannabinoids in the management of acute pain is
mixed (see Section 4.3.8). Although anecdotal reports suggest higher opioid doses may be
required for the management of acute pain in patients who are heavy users of cannabinoids
there is no published information to support this.
11.8.3 CNS stimulant drugs
Abuse of CNS‐stimulant drugs (eg cocaine, amphetamines, ecstasy) is associated with a
psychological rather than physical dependence and only a low degree of tolerance; these
drugs do not exhibit any cross‐tolerance with opioids, and while behavioural and autonomic
effects are seen during acute exposure, withdrawal symptoms are predominantly affective
rather than physical.
Although cocaine and ecstasy (N‐Methyl‐3,4‐methylenedioxyamphetamine or MDMA) are
known to enhance the analgesic effects of morphine in animals (Kauppila et al, 1992; Gatch et al,
1999; Nencini et al, 1988), there are currently no data from human studies. In experimental pain
settings, subjects taking ecstasy have been shown to have a reduced pain tolerance (O'Regan &
Clow, 2004 Level III‐2) and those taking cocaine reduced cold‐pressor pain thresholds (Compton,
1994 Level III‐2). There are no data from the clinical setting of any difference in opioid
requirements compared from patients who do not use these drugs.
Withdrawal from methamphetamines is characterised by increases in sleepiness and appetite
that can last for a few days; the severity of sleepiness correlated with amount used (calculated
by cost per month) and length of regular use (McGregor et al, 2005).
11.8.4 Drugs used in the treatment of addiction disorders
Methadone
Methadone is a long‐acting opioid agonist used in the management of patients with an opioid
addiction. It is usually given once a day, which is often enough to suppress symptoms of opioid CHAPTER 11
withdrawal; the duration of any analgesic effect from the dose is likely to be much shorter
(Alford et al, 2006; Basu et al, 2007). Dividing the daily dose on a temporary basis (eg giving the
methadone in two equal doses twice a day) may allow some of the analgesic effect to be seen.
In the acute pain setting methadone should be continued, where possible, as usual at the
same dose. If there is any doubt about the dose (for example, there is a suspicion that the
patient is diverting part or the entire prescribed amount), it may be prudent to give part of the
reported dose and repeat this over the day if needed and if the patient is not sedated (Peng et
al, 2005). If the patient is unable to take methadone by mouth, substitution with parenteral
methadone or other opioids will be required in the short term (Mitra & Sinatra, 2004).
Parenteral methadone doses should be based on half to two‐thirds of the oral maintenance
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