pharmacology: Neuromuscular blockers

Neuromuscular blockers:

Drugs which can cause complete muscular paralysis or relaxation. there are 2 groups:

1. Competitive: characterized by long duration effects 
2. depolarizing neuromuscular: have short duration of effect.

 note: therapeutic use of these group of drug depends on the duraction of surgical procedure which we need muscular relaxation to perform. so for long duration like intraabdominal operation we will use competitive type; while for short procedure like Endotracheal intubation or electronconvulsive therapy we will use the depolarizing one (e.g., succinylicholine or suxamethonium)

note: depolarizing neuromuscular blocking agents usually given by IV infusion; because of their short duration effect.

note: after given of succinylcholine; at the beginning there will be muscular contraction; then after exhaustion of the muscle there will be relaxation.

adverse effects:

• bradycardia
• increase intraocular pressure 
• prolonged paralysis 
• malignant hyperthermia

bradycardia:
succinylcholine has muscurinic agonist activity similar to acetycholine; meaning that it can produce arrhythmia; and this might due to increase in plasma potassium level (hyperkalemia); that's why succinylcholine should be avoided in patient with severe muscular damage or tramua; becasue in these condition the plasma (blood) potassium is elevated.

Increase intraocular pressure:
succinylcholine may lead to increase introcular pressure; so its better not to use it in operation of eyeball; because it will lread to extravasation of intraocular fluid due increase in pressure

Prolonged paralysis:
these cases has been reported after treatment with succinlycholine; but only in patient with specific cases:

• patients who are genetically predisposed to have choline esterase deficiency (hypocholine esterasemia); so if there is a decrease in this enzyme (meaning choline esterase); the succinylcholine will stay for longed period in plasma or tissue; giving along duration of effect; prolonged paralysis 
• patients who receives anticholine esterase drugs 
• neonates and patients with their live disease; might have prolonged apnea; because in these group of patient there is inefficient metabolism of succinylecholine. 

Malignant hyperthermia: 
when used in patient who are receiving halogenated hydrocarbon for their general anethesia; some of theme may develop malignant hyperthermia