Atropine

CNS: 

• Low doses: Minimal stimulant effects. 
• In toxic/high doses: Maximal excitaory effect.
• Cause excitement, agitation, hallucinations, & coma.  
• Reduces Parkinson’s tremor.

Eye: 

• Mydriasis – Paralysis of sphincter pupillae.
• Cycloplegia – Paralysis of accommodation.
• Abolition of light reflex.
• Photophobia & blurring of near vision.
• Increased intraocular pressure in people with shallow anterior chamber.
• It gives comfort & rest to eye by relieving spasm of iris sphincter & ciliary muscle.
• Prevents synechiae formation & demolishes already formed synechiae.
• Increases blood supply to anterior uvea.
• By relieving pressure on anterior ciliary arteries.

CVS:  

• Tachycardia – Due to M2 bloackade.
• Heart rate decreases transiently.
• Counteracts the peripheral vasodilation and sharp fall in blood pressure caused by choline esters.
• Increased A-V conduction

GIT:

• Inhibitory effects on motor activity of the stomach, duodenum, jejunum, ileum, and colon. 
• Reduction in tone and in amplitude and frequency of peristaltic contractions
• Cause relaxation of LES.

Respiratory System:

• Causes bronchodilatation.
• Reduces airway resistance (In COPD & asthma)
• Inhibits secretions of nose, mouth, pharynx, & bronchi. 
• Inhibits mucociliary clearance. 
• Dry secretions result in mucus plugs. 

Excretory system:

• Relaxant action on ureter & urinary bladder.
• Urinary retention in older males with prostatic hypertrophy.

Secretions: 

• Reduces salivary, lacrimal and gastric secretions.
• Due to M3 blockade.

ADVERSE EFFECTS:

• Due to extension of its pharmacological actions.
• Dryness of mouth, difficult swallowing
• Tachycardia
• Fever
• Constipation
• Blurring of vision – Glaucoma (elderly)
• Retention of urine (elderly)
• Local allergy: Dermatitis, conjunctivitis, swelling of eyelids

Festooned pupil:

• Due to irregular dilatation of pupil with atropine in presence of segmental posterior synechiae.

USES:

• As an anti-spasmodic drug.

In eyes:

• As mydriatic and cyclopegic, both for diagnostic & therapeutic purposes.
• Fundoscopic examination
• Acute iritis
• Iridocyclitis
• Fungal corneal ulcer
• Keratitis

Pre-anesthetic medications:

• Reduce secretions.

As an anti-dote:

• OP poisioning (competitive antagonist of acetylcholine)
• Mushroom poisoning
• Carbamates poisoning
• In Parkinsonism

CVS: 

• As a cardiac vagolytic:
• Useful in AV block, bradycardia.
• Urinary incontinence.
• Motion sickness
• Hyosine – most effective drug.
• Prophylactically 0.2 mg orally.

CONTRAINDICATION:

Age > 40yrs.

• In patients with narrow iridocorneal angle.
• May precipitate acute congestive glaucoma.
• Elderly patient with prostatatic hypertrophy.
• Fear of urinary retention.
• Cyanosed patient.
• due to danger of respiratory arrest

BELLADONA POISIONING:

• Resultant of drug overdose/consumption of seeds & berries of belladonna/datura plant.
• Children highly susceptible.

Lethal drug dose: 

• Children: 10-30mg.
• Adults: 80-130mg

Peripheral muscarinic blockade

• Dryness of mouth, difficult swallowing, thirst
• Tachycardia, palpitations
• Hyperpyrexia (inhibition of sweating)
• Dilatation of pupils, blurred vision, photophobia
• Urinary urgency, difficult micturition, retention
• Rash (Scarlet type) – face, neck , upper trunk

Central actions

• Excitement, restlessness
• Motor incoordination
• Slurring of speech, memory disturbance
• Confusion, hallucination, mania, delirium
• Hypotension.
• Coma, paralysis of resp centre

Diagnosis

• Methacholine 5 mg or neostigmine 1 mg s.c. fails to induce typical muscarinic effects.
• Pupillary dilatation.

Treatemnt:

Ingestion: 

• Gastric lavage with Tannic acid.
• Physostigmine 1-4mg (children 0.5-1mg) IV (preferred in CNS symp)
• Neostigmine 2-5mg sc (No effect on CNS symp.)
• Diazepam to control convulsions.
• Repeated at intervals of 1-2hrs
• Other symptomatic management:
•  Dark room, tepid sponging, oxygen, artificial ventilation, catheterisation.