VPT 321: Veterinary Neuropharmacology (2+1) copy 1

INTRODUCTION

Local anaesthetics

• Agents applied locally to skin / mucosa for reversible blockade of the nerve impulses – they effectively block the somatic sensory, somatic motor, and ANS
• No need for general anaesthesia (GA) – surgery performed in standing posture with or without sedation –
• avoids prolonged recumbency and
• no specialized equipment or technique required and easy to practice
• Initially, in 1860 cocaine was  isolated from Erythroxylum coca – numbing of tongue (Niemann).
• Koller introduced it into surgery (1884)
• -- not used now– toxic and addictive

Ideal properties of a LA

• Should produce reversible paralysis
• Should be non addictive
• Should be readily soluble and stable in water
• Non irritant to the skin
• Minimal toxicity
• Compatible with epinephrine
• Slowly absorbed to have long duration of action
• Inexpensive
• Not induce hyperesthesia

Comparison of GA and LA

General anaesthetic	Local anaesthetic
Site of action CNS	Peripheral nerves
Whole body is involved	Restricted area is involved
Consciousness is lost	Consciousness is retained
Care of vital functions essential	Care of vital functions not needed usually
Risky in poor health	Safer even in poor health
Physiological trespass is high	Physiological trespass is low
Preferred for major surgeries	Not preferred (only minor surgeries can be performed)