Local Anaesthetics 115

Local anaesthetics reversibly block impulse
conduction in a restricted area of the body
where it is applied by topical application or
local injection. They are classified as in table
2.8.1.

All the local anaesthetics possess vary-
ing degree of water and lipid solubility. Both
the properties are essential for a local anaes-
thetic, lipid solubility helps in migration of
active drug into the neuronal fibre and wa-
ter solubility is essential to get the drug to
site of action from the site of administration.

Local anaesthetics are employed

routinely in dentistry by nerve block or by

infiltration and/or regional block techniques

to cary out varous operative procedures.

Local anaesthetics can also be classified

into two categories based on their chemical

structure:

a. Ester linked local anaesthetics e.g. co-

caine, procaine, tetracaine, benzocaine,

chloroprocaine.

b. Amide linked local anaesthetics e.g.

lidocaine, bupivacaine, dibucaine,

prilocaine, ropivacaine.

(Mode of Action of Drugs)

PharmacodynamicsPharmacodynamicsPharmacodynamicsPharmacodynamicsPharmacodynamicsPharmacodynamicsPharmacodynamicsPharmacodynamicsPharmacodynamicsPharmacodynamics

Chapter

1.4

Chapter

2.8 Local Anaesthetics

Local

Anaesthetics

Table 2.8.1: Classification of local anaesthetics.

I. Used topically

Lignocaine (XYLOCAINE) 1-5% (as ointment, jelly & topical solution)

Benzocaine (MANDELAY) 5% ointment

Tetracaine (ANETHANE) 0.25-0.5% (powder & ointment)

Dibucaine (NUPERCAINAL) 1% ointment

Oxethazaine (MUCAINE GEL) 2% suspension

II. Used parenterally

Procaine (NOVOCAINE) 0.5-2% inj

Lignocaine (XYLOCAINE) 0.5-2% inj, 5% for spinal anaesthesia

Tetracaine (ANETHANE) 0.25-0.5%

Bupivacaine (SENSORCAINE) 0.25-0.5% inj, 0.5-0.75% for spinal anaesthesia

Dibucaine (NUPERCAINE) 0.1-0.5%, 0.25-0.50% for spinal anaesthesia

Newer compounds are prilocaine, ropivacaine, etidocaine etc.