DRUGS
ACTING ON PERIPHERAL NERVOUS SYSTEM
PREPARED BY MR. ABHIJIT DAS
ADRENERGIC DRUGS
Adrenergic drugs are agents that activate the sympathetic
nervous system by stimulating the release of adrenaline
(epinephrine) and noradrenaline (norepinephrine). These drugs are also
known as sympathomimetic drugs.
CLASSIFICATION:
·
Direct-acting:
Directly stimulate adrenergic receptors.
Examples: Epinephrine, Norepinephrine, Salbutamol
·
Indirect-acting:
Increase the release of noradrenaline from nerve endings.
Examples: Amphetamine, Tyramine
·
Mixed-acting:
Both directly stimulate receptors and increase noradrenaline release.
Examples: Ephedrine, Pseudoephedrine
PHARMACOLOGICAL ACTIONS:
Ø Heart:
- Increases
heart rate and force of contraction.
Ø Blood
Vessels:
- Narrows
blood vessels (Vasoconstriction), raising blood pressure.
- Expands
vessels (Vasodilation) in muscles, improving blood flow.
Ø Lungs:
- Widens
airways (Bronchodilation), making breathing easier.
Ø Eye:
- Dilates
pupils.
- Lowers
eye pressure in glaucoma.
Ø GI
Tract:
- Slows
digestion by reducing movement.
- Tightens
digestive tract sphincters.
Ø Urinary
Tract:
- Relaxes
bladder, making it harder to urinate.
Ø Metabolism:
- Increases
blood sugar.
- Enhances
fat breakdown for energy.
ADVERSE EFFECTS:
a)
Increased heart rate (tachycardia)
b)
High blood pressure (hypertension)
USES:
a)
Treatment of asthma (bronchodilation)
b)
Management of shock (to raise blood
pressure)
CHOLINERGIC DRUGS
Cholinergic drugs are agents that activate the parasympathetic
nervous system by stimulating the release of Acetylcholine. These
drugs are also known as parasympathomimetic drugs.
CLASSIFICATION:
· Direct-acting:
Act directly on cholinergic receptors.
Examples: Pilocarpine, Bethanechol
· Indirect-acting:
Inhibit acetylcholinesterase, increasing acetylcholine levels.
Examples: Neostigmine, Physostigmine
PHARMACOLOGICAL ACTIONS:
Ø Eye:
· Constricts
pupils (miosis)
Ø Heart:
· Slows
heart rate (bradycardia)
· Reduces
force of contraction
Ø Lungs:
· Causes
bronchoconstriction
Ø GI
Tract:
· Increases
motility and secretion
· Relaxes
sphincters
Ø Urinary
Tract:
· Promotes
urination by contracting the bladder and relaxing sphincters
Ø Glands:
· Increases
secretion (sweat, saliva, tears)
Ø CNS:
· Improves
cognition
ADVERSE EFFECTS:
a)
Bradycardia
(slow heart rate)
b)
Excessive salivation
Uses:
a)
Treatment of glaucoma
(e.g., Pilocarpine)
b)
Treatment of urinary retention
(e.g., Bethanechol)
ANTI ADRENERGIC DRUGS
Anti-adrenergic drugs, also called sympatholytic
drugs, block the effects of the sympathetic nervous system. They
work by inhibiting adrenergic receptors, reducing the action of adrenaline
and noradrenaline in the body.
CLASSIFICATION:
Ø Alpha
Blockers
- Alpha-1
Blockers: Example: Prazosin, Doxazosin
- Alpha-2
Blockers: Example: Yohimbine
Ø Beta
Blockers
- Non-selective
Beta Blockers: Example: Propranolol
- Selective
Beta-1 Blockers: Example: Metoprolol
Ø Mixed
Alpha and Beta Blockers
- Example:
Carvedilol, Labetalol
PHARMACOLOGICAL ACTIONS:
Heart
- Decrease
heart rate: By reducing the force and rate of
heart contraction.
Lungs
- Bronchoconstriction:
Non-selective beta blockers can cause narrowing of airways.
Eye
- Pupil
constriction (miosis)
GI
- Increase
gastrointestinal motility: By relaxing
sphincters and promoting digestion.
ADVERSE EFFECTS:
a)
Bradycardia
(slow heart rate)
b)
Bronchoconstriction
(difficulty breathing, especially in asthmatic patients)
USES:
a)
Hypertension
(to lower blood pressure)
b)
Angina (to
reduce chest pain and improve heart function)
ANTI CHOLINERGIC DRUGS
Anti-cholinergic drugs, also known as parasympatholytic
drugs, block the effects of the parasympathetic nervous system by
inhibiting cholinergic receptors.
CLASSIFICATION:
Ø Muscarinic
Antagonists
- Example:
Atropine, Scopolamine
Ø Nicotinic
Antagonists
- Example:
Curare, Pancuronium
PHARMACOLOGICAL ACTIONS:
Heart
- Increase
heart rate
Lungs
- Bronchodilation
Eye
- Pupil
dilation (mydriasis)
GI
- Decrease
gastrointestinal motility
Urinary Tract
- Reduce
bladder contractions: Used in treating overactive
bladder.
ADVERSE EFFECTS:
a)
Dry mouth
b)
Blurred vision
USES:
a)
Treatment of motion sickness
(e.g., Scopolamine)
b)
Management of overactive bladder
(e.g., Oxybutynin)