Local Anesthetics

Question 1

What is a local anesthetic?

Answer 1

Drugs that reversibly block nerve conduction

When applied locally on nerve tissue

In appropriate concentrations

Question 2

What are the types of local anesthetics?

Answer 2

Amides (better)

Esters

Amides
Lignocaine
Bupivacaine
Prilocaine

Esters
Cocaine (alkaloid)
Procaine

Question 3

What are the desirable properties of local anesthetic?

Answer 3

Water soluble

Sterilizable by heat

Rapid onset

Appropriate duration of action

Non toxic locally and systemically

No after effects

Question 4

What is the mechanism of action of local anesthetic?

Answer 4

Use dependent block

Of voltage gated Na+ channels

In sensory, motor and autonomic fibers

Small fibers > large fibers

Question 5

What are the important pharmacokinetics of local anesthetic?

Answer 5

Fast onset within 5 mins

Duration 2 hours

Stable acid salts (less active in acidic tissue)

Metabolized in liver

Excreted in urine

Mostly vasodilators (except cocaine)

Used with 1:200,000 adrenaline to delay systemic absorption and toxicity, increases duration of action, allows higher concentrations

Question 6

What are the indications for local anesthetic?

Answer 6

Minor surgery that doesn’t need loss of consciousness

Adjunct to major surgery

Postop analgesia

Question 7

What are the precautions when using local anesthetic?

Answer 7

Aspirate before injecting

Don’t give to infected sites

Cardiotoxic

Don’t give to infants

No Adrenalin in CVD

Question 8

What are the side effects of local anesthetics?

Answer 8

Paresthesia

Anxiety

Tremor

Convulsions

Respiratory depression

Cardiovascular collapse

Hypersensitivity to esters (not amides)