Neuromuscular junction blocker/Skeletal muscle relaxant

Introduction

DefinitionThese are the Drug produce relaxant of skeletal muscle by inhibitingthe transmission of nerve impulse at neuromuscular junction

History CURARE:- it is the generic name for certain plant extracts used by South America tribal's as arrow poison for game Hunting. the animal get paralyzed even if not killed. natural source of curare- Strychnos toxifera, - Chondrodendron tomentosus

Uses• general anesthetics to provide muscle Relaxant for surgery•Painful muscle spasms•Spastic neurological condition

Classifications

I. Neuromuscular Blocking Agent A. Nondepolarizing (Competitive) blockers) 1.Long acting: d-Tubocurarine, Pancuronium, Doxacurium, Pipercuroniun 2. Intermediate acting: Vecuronium, Atracurium, Cisatracurium, Rocuronium Rapacuronium 3. Short acting: Mivacurium B. Depolarizing blockers -Succinylcholine, DecamethoniumII. Directly acting agent -Dantrolene sodium -Quinine

d-Tubocurarine

Source: (CURARE) Chondrodendron tomentosus, Strychnos lethalisIt is dextro rotatory competitive blockers.Mainly used as an Arrow poison in hunting animals

MOA

It binds to the Nicotinic receptors on the motor end plate N thus blocks the action of Ach by competitive blockadeIf the concn of Ach varies (increase) d- Tubocurarine bockade is reversed

Pharmacological ActionSkeletal muscle initially paralyses smaller muscle (finger, toes eyes ear)

latter bigger muscle (limbs, neck, trunk followed by intercostal muscles)

Diaphragm is affected at last N recovery is reversed.

CNS don’t cross BBB & PB i.e no effect on CNS

Autonomic ganglia partially blockade both autonomic ganglia & adernal medulla resulting fall of B.P

Histamine Release directly act on mast cell & produce Histamin causes >bronchospasm >increase salivary >gastric acid seceration

Pharmacokinetics:

A not absorb from GIT but well absorbed through IM D doesn't pass BBB &PB M in liver E urine

ADR