Pethidine (INN, AAN, BAN) or meperidine (USAN) was once a popular synthetic opioid analgesic of the phenylpiperidine class. Synthesized in 1939 as a potential anticholinergic agent by the German chemist Otto Eisleb, its analgesic properties were first recognized by Otto Schaumann while working for IG Farben, Germany.
Pethidine is indicated for the treatment of moderate to severe pain, and is delivered as a hydrochloride salt in tablets, as a syrup, or by intramuscular, subcutaneous, or intravenous injection. For much of the 20th century, pethidine was the opioid of choice for many physicians; in 1975, 60% of doctors prescribed it for acute pain and 22% for chronic severe pain.
Compared with morphine, pethidine was thought to be safer, carry a lower risk of addiction, and to be superior in treating the pain associated with biliary spasm or renal colic due to its putative anticholinergic effects. These were later discovered to be all myths, and it carried an at least equal risk of addiction, possessed no advantageous effects on biliary spasm or renal colic compared to other opioids, and due to its toxic metabolite, norpethidine, was more toxic than other opioids, especially during long-term use. The norpethidine metabolite was found to have serotonergic effects, so pethidine could, unlike most opioids, contribute to serotonin syndrome.