Ester Local Anesthetics

Ester local anesthetics are used commonly to anesthetize body parts by local infiltration or by surface absorption in order to relieve painful conditions or to assist in completion of procedures.  Esters are metabolized by plasma cholinesterase.  In patients with pseudocholinesterase deficiency, metabolism may be prolonged.  Systemic toxicity is more likely for amide anesthetics than esters.

(A hint for classifying amide vs ester anesthetics: all amide anesthetics have 2 i's in their spelling.)

Class Drugs

• Procaine

• Tetracaine

• Chloroprocaine

• Cocaine

• Benzocaine

Class Mechanism of Action

Block nerve conduction sensory impulses from the periphery to the CNS

• Blockade of sodium ion channels

Prevents action potential from initiating and sending signals to the brain

• Causes vasodilation

This side effect is mitigated by co-administration of epinephrine, which limits diffusion by causing vasoconstriction

Class Application

Local anesthesia

• Via: topical administration, infiltration, nerve blocks, or neuraxial blocks (epidurals, etc.)

Class Adverse Effects

Systemic toxicity

• May be caused by overdose of local injection or iv injection of appropriate doses

• Treatment is generally supportive

Airway management

• Treatment of seizures

• Treatment of cardiac arrhythmias

• In severe cases lipid emulsion therapy rescue is indicated

Allergy

• Allergies are rare to local anesthetics, esters are more allergenic than amides

• Allergy to one ester rules out use of other esters as the allergic component is the same (para-aminobenzoic acid)

Drug Table

Drug Name	Application	Comments	Image
Procaine			"Pro" "Cane"
Tetracaine			"Tetris" "Cane"
Chloroprocaine			"Chlorine" "Cane"
Cocaine			"Coke" "Cane
Benzocaine		Adverse Reactions; Methemoglobinemia	"Mercedes-Benz logo" "Cane"