ATROPINE

1) Action

• Parasympatholytic; anticholinergic

2) Mechanism

• Cholinergic-blocker; Muscarinic receptor blocker

• Causes reversible blockage of Ach at muscarinic receptors

• Central & peripheral actions

• Blocks vagal stimulation of heart

3) Indications

• Premed to decrease salivary & bronchial secretions & to diminish risk of vagal inhibition of heart

• Bradycardias

• Concurrently with anticholinesterases (eg neostigmine) to block adverse muscarinic effects

• Organic phosphate cholinesterase inhibitor poisoning (insecticide)

4) Effects on organs—side effects

• Reduces salivary, sweat, GIT and bronchial secretions

• Relaxes smooth muscle [esp GIT]

• Dilates pupil

5) Toxic effects/ precautions with administration

• Anticholinergic effect exacerbated by other drugs with anticholinergic effects eg antihistamines, phenothiazines, tricyclics, butyrophenones

• Toxic doses associated with mental disturbances [delirium, hallucinations]

6) Contraindications

• GIT obstruction

• Tachycardias

• Asthma

7) Reversal, antagonism or antidote

• Barbiturate or benzodiazepine for CNS excitement

8) Loading dose, maintenance dose, frequency & method of administration

• Pre anaesthetic: 0.4 - 0.6 mg

• Vagal block:1.5 - 2 mg

9) Drug’s metabolism—Drug’s excretion—Half life (pharmacokinetics)

• Ampoules: 600 mcg/ml; 1.2 mg/ml

• Elimination half life: 25 min

• % plasma protein binding: 30-50