Pethidine
| Pethidine |
Pethidine is a synthetic phenylpiperidine opioid agonist, structurally dissimilar to morphine. It has low oral bioavailability, and is more lipophilic than morphine, with faster onset and shorter duration of action after parenteral administration.
Pethidine is unsuitable for the relief of chronic pain, and it should not be used for more than 72 hours for shorter-term analgesia. It has been removed from the Pharmaceutical Benefits Scheme (including from the doctor’s bag emergency drug supply list) and from a number of Australian hospitals as it has shown no advantage compared to other parenteral opioids and has a number of significant disadvantages. These disadvantages include:
- Accumulation of the active metabolite, norpethidine, can cause hyperexcitability, tremors, myoclonus and seizures, especially with repeated dosing or renal impairment.
- Its effect on the sphincter of Oddi is similar to morphine—there is no evidence to support the preferential use of pethidine in gall bladder or pancreatic disease.
- There is no evidence that pethidine is better than morphine in the management of renal colic or obstetric pain.
- Pethidine can cause serotonin syndrome when combined with other serotonergic medication
It has a higher potential for abuse.
Absorption of intramuscular pethidine is extremely variable in postoperative patients. Regular intramuscular use postoperatively is associated with widely fluctuating plasma concentrations and variable levels of analgesia.
Pethidine should be avoided, because of its short duration of action, its neurotoxic metabolite (norpethidine), and its high propensity to induce drug-seeking behaviour.
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