DRUGS ACTING ON AUTONOMIC NERVOUS SYSTEM
Introduction:
The autonomic nervous system controls involuntary body functions such as heart rate, respiration, digestion, glandular secretion, and smooth muscle activity. Drugs acting on this system modify these functions by stimulating or blocking nerve responses.
Sympathomimetic Drugs (Adrenergic Agonists):
These drugs stimulate adrenergic receptors and mimic the action of epinephrine and norepinephrine. They may act directly or indirectly.
Classification Based on Use:
- Vasoconstrictors: Norepinephrine, Metaraminol
- Cardiac stimulants: Dopamine, Dobutamine
- CNS stimulants: Amphetamine
- Smooth muscle relaxants: Epinephrine, Isoprenaline
- β2 agonists: Salbutamol
- Anti-allergic agents: Epinephrine, Ephedrine
- Local vasoconstrictors: Phenylephrine
- Appetite suppressants: Phentermine
Direct Acting Agents:
Act directly on α and β receptors.
- Norepinephrine
- Epinephrine
- Phenylephrine
- Dopamine
- Salbutamol
Norepinephrine: Causes vasoconstriction and increases blood pressure in hypotension.
Indirect Acting Agents:
Release stored norepinephrine from nerve endings.
- Pseudoephedrine
- Hydroxyamphetamine
Pseudoephedrine: Used as nasal decongestant and mild bronchodilator.
Mixed Acting Agents:
Act directly and also release norepinephrine.
- Ephedrine
- Metaraminol
Ephedrine: Used in asthma, hypotension, and allergic reactions.
Adrenergic Antagonists (Sympatholytics):
Block adrenergic receptors and reduce sympathetic activity.
- α-blockers: Prazosin, Phentolamine
- β-blockers: Propranolol, Atenolol
Propranolol: Used in hypertension, arrhythmia, anxiety, and migraine.
Cholinergic Drugs (Parasympathomimetics):
Mimic acetylcholine and stimulate muscarinic or nicotinic receptors.
- Direct acting: Acetylcholine, Pilocarpine
- Indirect acting: Neostigmine, Edrophonium
Pilocarpine: Used in glaucoma and dry mouth.
Cholinergic Antagonists (Parasympatholytics):
Block muscarinic receptors and reduce parasympathetic activity.
- Atropine
- Ipratropium
- Tropicamide
- Dicyclomine
Ipratropium: Used as bronchodilator in COPD.
