Cholinergic Antagonist:

These bind to cholinergic receptors and block them. They are also called parasympatholytics, cholinergic blockers or anticholinergic drugs'

Classification:

ATROPINE:

It is a tertiary amine extracted from belladonna alkaloid. It has a high affinity for muscarinic receptors binds competitively to prevent acetylcholine from binding. Half-life is 4 hours.

ACTIONS:

EYE:

Atropine causes dilation of pupil called mydriasis, unresponsiveness to light and cycloplegia. It increases intraocular pressure.

GIT:

It is antispasmodic to reduce the activity of the GIT. It reduces secretions and relieves intestinal and biliary colics.

CNS:

It causes excitement, hallucinations and delirium.

URINARY SYSTEM;

It decreases the tone of the smooth muscle of the bladder and causes urinary retention.

CVS:

It has a divergent effect on the heart. At a low dose, it decreases heart rate. At a high dose, it increases heart rate.

SECRETIONS:

It blocks the salivary glands causing xerostomia. It also decreases sweat and lacrimal glandular secretion.

Therapeutic uses:

Ophthalmic:

It causes both mydriatic and cycloplegic effects. It is used in the measurement of refractive errors.

Antispasmodic

Bradycardia

Anti secretory

Anti dote for cholinergic agonist

Adverse effects:

Dry mouth

Blurred vision

Tachycardia

Urinary retention

Constipation

Restlessness

Confusion

Hallucinations

Signs of atropine toxicity:

Hot as a hare ( hyperthermia)

Dry as bone( dry skin)

Red as a beat(flushed)

Blind as a bat(mydriasis)

Mad as a hatter(delirium)

The antidote of atropine:

Physostigmine

                      

                                     Scopolamine

It is also a tertiary amine produces similar effects to those of atropine but has greater effects on CNS.

Clinical uses:

Scopolamine is used to prevent motion sickness, postoperative nausea and vomiting.