الحلقة 8 من كورس كلنيكال فارما (ANS)

Antinicotinic Agents

Ganglionic Blockers (GB)

- They are drugs which block nicotinic receptors of both sympathetic

parasympathetic autonomic ganglia (no selectivity toward the parasympathetic or

sympathetic ganglia).

- Ganglionic blockers is rarely used therapeutically, but often serves as a tool in

experimental pharmacology because they can block all autonomic outflow.

- Classification according to mechanism of action.

A) Depolarizing GB: -

First in stimulation and then in paralysis of all ganglia i.e. Stimulation→

prolonged stimulation→ paralysis of ganglia.

B) Non-Depolarizing GB (Competitive):

Inhibition of postganglionic action of ACh.

Pharmacological Effect of Ganglion-Blocking Drugs:-

CNS - Sedation, tremor, choreiform movement and mental aberrations.

Eye

Ciliary muscle → Primary innervated by parasympathetic→ block ganglia in

parasympathetic ciliary muscle fiber cause→ Cycloplegia.

- Iris → Parasympathetic and sympathetic innervation → parasympathetic tone

usually dominates → block ganglia cause → Moderate mydriasis.

CVS

- Arterioles & Veins (direct innervated by sympathetic)→ block ganglia cause

→ marked decrease in arteriolar and venomotor tone→ Hypotension

(Orthostatic).

- Heart (SA node usually dominated by parasympathetic) → Moderate

tachycardia.

GIT - GIT → decrease GI secretions (not significant decrease in gastric acid secretion)

and decrease GI motility→ Constipation.

Urinary

bladder

- Urinary bladder relaxation of bladder wall and contraction of sphincter

→ Urinary retention.

Exocrine

glands

- Salivary gland (Parasympathetic)→ Decrease salivation (xerostomia).

- Sweat gland (Sympathetic)→ Decrease sweating.

Male sex

organs

- Erection (Parasympathetic)→ Impotency (decrease erection).

- Ejaculation (Sympathetic) →Failure of ejaculation.

Depolarizing Ganglionic Blockers

Nicotine Lobeline

- Nicotine and lobeline are tertiary amines found in the leaves of tobacco and

lobelia plants.

They are stimulates nicotinic receptors in small dose → prolonged stimulation with

dose increased → paralysis (desensitization) of ganglia →(blocker effect).

- No therapeutic uses, except for nicotine to assist given up smoking.

Non-Depolarizing Ganglionic Blockers (Competitive)

Tetraethylammonium

(TEA)

Hexamethonium Pentamethonium

-Quaternary ammonium Compound (QAC)→ Don't pass BBB.

- Used as a tool in experimental pharmacology.

Pempidine Tertiary amine (Non polar) → Pass BBB.

Trimethaphan (Arfonad®) Mecamylamine (Inversine)

- Mono sulfonium (S+)

- Don't pass BBB

- Ultra short duration of action(10 to 15 min.)

- Not given orally (IV)

- Treatment emergency hypertension

(hypertensive crisis)

- Cause histamine release→ Flushing

-Secondary amine

- Pass BBB

- Longer duration of action

- Given orally

- Treatment hypertension (moderate

hypertension )

- Not cause histamine release 

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