SAR of Meperidine Analogues

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Chapter: Medicinal Chemistry : Narcotic Analgesics

Placement of m-hydroxyl group on the phenyl ring increases activity. The effect is more significant on the keto compound than on the pyridine.


SAR of Meperidine Analogues



  • Placement of m-hydroxyl group on the phenyl ring increases activity. The effect is more significant on the keto compound than on the pyridine.

  • Substitution of carbethoxy group in meperidine by acyloxy group provides better analgesic as well as spasmolytic activity (alpha prodine).

  • The presence of phenyl and ester group at 4th position of 1-methylpiperdine results in optimum activity.

  • The replacement of C-4 phenyl group of meperidine by hydrogen, alkyl, other aryl, aralkyl, and hetero cyclic groups reduces analgesic activity.

  • Replacement of phenyl group by phenyl ethyl derivatives is seen to be about three times as active as the meperidine. The amino analogue, anileridine is about four, times more active.

  • Contraction of piperidiene ring to the pyrrolidine gives a more active compound, but causes abuse liability. For example, alphaprodine and procilidine.

  • Enlargement of piperidine ring to a 7-membered hexa hydroazepine yield active compounds with low incidence of side effects. For example, Proheptazine.

  • The C-3 methyl analogue with an ester group at the C-4 position like lofentanil 8,400 times more potent than meperidine as an analgesic.

  • In fentanyl, the phenyl and acyl groups are separated by nitrogen. It is 50 times stronger than morphine with minimal side effects. Its short duration of action makes it well suited for use in anaesthesia.

  • The p-chloro analogue (loperamide) has been shown to bind to opiate receptors in the brain, but it cannot penetrate the blood-brain barrier sufficiently to produce analgesia.

  • Diphenoxylate, a structural hybrid of meperidine and methadone type, devoid of analgesic activites. It is effective as an intestinal spasmolytic and is used in the treatment of diarrhoea.

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