Amide Local Anaesthetics

All local anaesthetics have a lipid-soluble ring (Fig 1a) linked to an amine-containing group (Fig 1b). The two groups of local anaesthetic differ in the type of linkage.

The general structure of local anaesthetics and the amide linkage is shown in Fig 1c. The amide link is more stable than the ester linkage.

The following agents are all amide local anaesthetics:

Lidocaine
Bupivacaine
Prilocaine
Ropivacaine

Amide local anaesthetics (Fig 2) are more highly protein-bound than ester local anaesthetics, which correlates with a longer duration of action.

Fig 1a Lidocaine local anaesthetic (lipid soluble ring)

Fig 1b Lidocaine local anaesthetic (amine-containing group)

Fig 1c Lidocaine local anaesthetic (amide linkage)

Fig 2 Amide local anaesthetics