The document discusses drugs that affect the sympathetic nervous system. It describes both sympathetic stimulants and depressants. Sympathetic stimulants include adrenaline, noradrenaline, and dopamine. Sympathetic depressants are classified into adrenergic receptor blockers, adrenergic neuron blockers, ganglion blockers, and central sympathetic depressants. Specific drugs discussed in depth include prazosin, an alpha-adrenergic receptor blocker used to treat hypertension, and propranolol, a non-selective beta-adrenergic receptor blocker used for cardiovascular diseases. Side effects and therapeutic uses are provided for various sympathetic drugs.

1. Sympathetic
System
DR/ Dina Medhat Elhantery
Helwan University

2. Distribution & effect of sympathetic nervous
system:

4. - Drugs That Affect Sympathetic System
• Are classified into:
I- Sympathetic Stimulant “Sympathomimetics” (drugs that
produce effects similar to sympathetic nerve stimulation).
1- Adrenalin
2- Noradrenalin
3-Dopamine
4- Ephedrine
5- Amphetamine
6-Salbutamol.

5. II- Sympathetic Depressant “Sympatholytics”
Classifications:
• I- Adrenergic receptors blockers:
1- Alpha blockers e.g. phentolamine.
2- Beta blockers e.g. propranolol.
3- Alpha & Beta blockers e.g. labetalol
• II- Adrenergic neuron blockers:
1- Drugs inhibit synthesis e.g. alpha-methyl dopa.
2- Drugs inhibit storage e.g. reserpine.
3- Drugs inhibit release e.g. guanethidine.

6. • III- Ganglion blockers e.g. trimetafan.
• IV- Central sympathetic depressant:
Drugs act centrally by stimulating alpha 2 (α2)- receptors →
inhibiting noradrenaline release e.g. clonidine

7. Adrenaline
• Adrenaline is secreted from adrenal medulla.
• Not absorbed after oral intake (adrenaline is destroyed by
gastric secretion).
• s.c.: slow absorption (adrenaline produces vasoconstriction of
skin blood vessels).
• i.m: rapid absorption (adrenaline produces vasodilatation of
skeletal muscles vessels).

8. • Mechanism of action:
Adrenaline is a non-selective agonist for all adrenergic receptors.
• Local: applied on mucus membrane it produces decongestion. It can
stop bleeding from nose (hemostasis).
• Systemic : Adrenaline stimulates the heart → ↑blood pressure.
• Smooth Muscles:
Airway: bronchodilatation.
Uterus: both contraction and relaxation depending on the menstrual
period and gestational stage.
• Histamine antagonism: Adrenaline is the physiological antagonist of
histamine.

9. • Therapeutic uses:
1. Adrenalin derivative (dipivefrin) in glaucoma.
2. Epistaxis (local application on m.m).
3. Bronchial asthma (s.c and inhalation) however, now is
replaced by β2 selective agonist.
4. Anaphylactic shock (adrenaline is life saving).
5. Cardiac arrest (adrenaline is injected intracardial).

10. • Adverse Effects:
1. CNS: anxiety, restlessness and tremors.
2. Eye irritation (with dipivefrin).
3. Gangrene of finger and toe (if adrenaline is injected around it
with local anesthetics).
4. Tachycardia, palpitation, angina and arrhythmia.
• Contraindications:
1. CVS disease as: hypertension, angina and arrhythmias.
2. Thyrotoxicosis.
3. Pulmonary embolism.
4. Around finger & toe with local anesthetics.

11. Sympathetic Depressant “Sympatholytics”
Classifications:
I- Adrenergic receptors blockers:
1- Alpha- adrenergic receptors blocker e.g. phentolamine.
2- Beta-adrenergic receptors blockers e.g. propranolol.
3- Alpha & Beta receptors blockers e.g. labetalol.

12. Sympathetic Depressant “Sympatholytics”
II- Adrenergic neuron blockers (anti-adrenergic drugs):
1. Drugs inhibit synthesis e.g. alpha-methyl dopa.
2. Drugs inhibit storage e.g. reserpine.
3. Drugs inhibit release e.g. guanethidine.
III- Ganglion blockers e.g. trimetafan.
IV- Central sympathetic depressant:
Drugs act centrally by stimulating alpha 2 (α2)- receptors →
inhibiting noradrenaline
release e.g. clonidine

13. Alpha-Adrenergic Blockers
• Classification:
1. Ergot alkaloid derivatives e.g. ergotamine.
2. Prazosin

14. Prazosin
• Prazosin is a competitive reversible α – adrenergic receptors
blocker.
• Blood vessels: vasodilatation and decrease blood pressure.
Therapeutic uses:
1. Essential hypertension.
2. Pheochromocytoma (Plus β– adrenergic receptors blocker).
3. Peripheral vascular diseases.
4. Senile enlarged prostate.
5. Congestive heart failure.

15. Prazosin
Side Effects:
1- Syncope and postural hypotension
2- Skin flush and nasal stuffness.
3- Failure of ejaculation.

16. Beta-Adrenergic Receptors Blockers
• Propranolol is a non selective beta adrenergic receptors blocker
• Therapeutic uses:
1. Cardiovascular diseases : Hypertension, angina pictoris, cardiac
arrhythmias.
2. Thyrotoxicosis (symptomatic treatment).
3. Prophylaxis against migraine headache.
4. In cases of social anxiety and phobia.
5. Essential tremors.

17. Adverse Effects:
1- Sedation, depression, sleep disturbances and bad dreams.
2- CVS: bradycardia, heart block, hypotension and heart failure.
3- Airway: bronchospasm and may precipitate bronchial asthma
in susceptible patients.
4- Metabolic: hypoglycemia and musk its warning symptoms in
diabetic patients.
5- Sudden stop of β– blocker → arrhythmias and hypertension.

18. • Contraindications:
1- CVS: heart block, sever heart failure, hypotension and
Prinzmetal’s (variant) angina.
2- Peripheral vascular diseases.
3- Bronchial asthma.
4- Uncontrolled diabetes mellitus

19. II- Parasympatholytic
Classification:
I- Natural alkaloid:
o Atropine
o Hyoscine
II: Synthetic Atropine substitutes:
For GIT: pirenzepine and Probanthine
For treatment of bronchial asthma: ipratropium
For treatment of parkinsonism: benzotropine
For eye: homatropine, eucatropine and tropicamide
For urinary tract: Emepronium

20. Atropine
• Atropine is a natural plant alkaloid.
• Atropine competes with acetylcholine at muscarinic receptors
(reversible antagonist)

21. Therapeutic uses:
1- Parkinsonism, motion sickness.
2- Fundal examination and eye infection.
3- Peptic ulcer, intestinal colic and diarrhea.
4- Bradycardia and digitalis toxicity.
5- Bronchial asthma.
6- Renal colic.
7- In organic phosphate poisoning.
8- In hyperhydrosis to inhibit over sweating.

22. Side Effects: (all are expected):
1. Blurred vision.
2. Atropine may precipitate glaucoma.
3. Dry mouth.
4. Flushed skin.
5. Tachycardia.
6. Constipation.
7. Urine retention.
8. Restlessness, confusion and hallucination (toxic dose).

23. Contraindications:
1. Senile prostate (benign enlarged prostate).
2. Glaucoma (angle closure glaucoma).