- Anticholinergics are those antagonize the effect of neurotransmitter (Ach) on autonomic effectors and in the CNS.
- The parasympatholytic drugs are bind to the cholinoreceptor (Muscarinic and nicotinic) and prevent the effect of Ach.
- Atropine sulphate is a tertiary amine (belladonna alkaloid).
- It binds competitively at binding site of the Ach.
- Atropine acts both centrally and peripherally.
- It shows CNS stimulant action, but not appropriate at low dose.
- Stimulate many medullary centres, vagal respiratory, vasomotor (controlling the internal diameter of blood volume).
- In high dose causes: Cortical excitation, Restlessness, Disorientation (A state of mental confusion), Hallucination and delirium (mental confusion).
- Tachycardia (Most prominent), due to blockade of M2 receptor at SA node.
- Topical ingestion of Atropine causes Mydriasis (Paralysis of sphincter pupillae).
- Paralysis of Accommodation (Cycloplegia)
- Increase in IOP.
- GIT relaxation: Mediated by M3 blockade.
- Contraction of stomach and intestine is reduced leads to constipation.
- Bronchodilation: Especially COPD and Asthma patient.
- Also antagonizes histamine, prostaglandin, leukotrienes, mediated vagal over activity.
- Relaxation of ureter and bladder.
- Atropine markedly decrease sweat, salivary tracheobronchial and lacrimal secretion by M3 blockade.
- Skin and eyes becomes dry, talking and swallowing may be difficult.
- Increase temperature, due to inhibition of sweating as well as stimulation of temperature regulating center in the hypothalamus.
- Mild anaesthetic action on the cornea.
- Sensitive to different organs and tissue: saliva, sweat, bronchial smooth muscle, heart smooth muscle, intestine, GIT.
- Rapidly absorbed from g.i.t.
- Freely penetrate cornea.
- Crosses BBB is somewhat restricted.
- About 50% metabolized in liver.
- Excreted unchanged in urine.
- t ½ 3-4 hours.
- Hyoscine is more completely metabolized and has better blood-brain barrier penetration.
- Pre-anesthetic medication: reduce excessive salivation and respiratory secretions.
- Peptic Ulcer: decrease gastric secretion and provide symptomatic relief in peptic ulcer.
- Gastritis, gastric hypermotility
- Bronchial asthma
- As Mydriatics and Cycloplegia
- Parkinsonism as an adjuvant to Levodopa.
- Antagonize muscarinic effects of anticholinesterase (Mushroom poisoning)
- Tertiary amine (alkaloid).
- Produce peripheral effect as well as CNS effects.
- Peripheral effect similar to Atropine, but greater action on CNS (longer action as compare to Atropine).
- Effective anti-motion sickness.
- Produce sedation (higher dose) and excitement.
- Euphoria (state of intense excitement and happiness)
- Motion sickness
- Postoperative nausea and vomiting