right<unk>  is quickly hydrolysed in the liver to<unk> c acid and is also demethylated to norpethidine, which has half the analgesic activity of<unk>  but a longer elimination half-life (8–12 hours); accumulating with regular administration, or in kidney failure. Norpethidine is toxic and has convulsant and hallucinogenic effects. The toxic effects mediated by the metabolites cannot be countered with opioid receptor antagonists such as naloxone or naltrexone, and are probably primarily due to norpethidine's anticholinergic activity probably due to its structural similarity to atropine, though its pharmacology has not been thoroughly explored. The neurotoxicity of<unk> 's metabolites is a unique feature of<unk>  compared to other opioids.<unk> 's metabolites are further conjugated with glucuronic acid and excreted into the urine. 600px
Pethidine
Esketamine
Ketamine
Fentanyl
Aceclidine
Nalorphine
Remifentanil
Procaine