ATROPINE

Atropine is found in the plant Atropa belladonna and it is the prototype of muscarinic antagonists.

Pharmacokinetics

Atropine is absorbed completely from all sites of administration except from the skin wall, where absorption is for limited extent; it has good distribution. About 60% of the drug is excreted unchanged in urine.

Pharmacodynamics

Atropine antagonizes the effect of acetylcholine by competing for the muscarinic receptors peripherally and in the CNS; therefore the effects of atropine are opposite to the acetylcholine effects.

Organ-system Effects:

CNS:       – lower doses produce sedation

• higher doses produce excitation, agitation and hallucination

Eyes:      – relaxation of constrictor pupillae (mydriasis)

• relaxation or weakening of ciliary muscle (cycloplegia-loss of the ability to accommodate)

CVS:       – blocks vagal parasympathetic stimulation (tachycardia)

• vasoconstriction

Respiratory: – bronchodilatation and reduction of secretion

GIT:        – decreased motility and secretions

GUS:      – Relaxes smooth muscle of ureter and bladder wall; voiding is slowed.

Sweat Glands: – suppresses sweating

Clinical Indications

Pre anesthetic medication -to reduce the amount of secretion and to prevent excessive vagal tone due to anesthesia.

As antispasmodic in cases of intestinal, biliary, and renal colic Heart block

Hyperhidrosis Organophosphate poisonings

Side effects

• Dryness of the mouth, tachycardia and blurred vision
• Retention of urine

Contraindications

• Glaucoma
• Bladder outlet obstruction.