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Meperidine (Demerol)


• Approved uses for meperidine (M) are
.    1) Post-operative shivering
.    2) Rigors
.    3) Short-term pain relief (<48 hours with no renal disease, must be allergic to all other opioids, and it should not be used in elderly patients)
• M is metabolized in the liver to normeperidine, a CNS excitotoxin with a half-life of 20 hours
• Normeperidine has a half-life of 85 hours in fetal and neonatal tissue, so don’t use in pregnant patients
• Normeperidine accumulates with prolonged use and can cause CNS toxicity
• Narcan does NOT reverse and may increase CNS hyperexcitability. Don’t use!
• Do not use in the presence of MAO inhibitors
• M can worsen tachycardia and hypotension
• It is the least potent of opiates
• Both M and morphine cause constriction of the sphincter of Oddi and the biliary tract
• M causes just as much respiratory depression as morphine
• Phenergan does NOT potentiate the analgesic effect of M or other opiates
• M is somewhat less constipating than morphine

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