Atropine (202) Flashcards
What type of medication is Atropine?
Anticholinergic.
It is a naturally occurring alkaloid, which is lipid-soluble, absorbed from the GIT and conjunctiva, and crosses the blood-brain-barrier.
How does Atropine work?
Atropine competitively antagonises the parasympathetic effects of ACh on muscarinic receptors, resulting in:
- ^HR via ^ intrinsic rate of the SA-node and conduction through the AV node
- Reducing smooth muscle contraction, resulting in pupillary dilation, reduced GI motility and reduced bladder tone
- Blocks exocrine gland activity causing V salivary, bronchial, gastric, and sweat secretions
What effect does Atropine have on the eyes?
- Pupils dilate and ciliary muscle relaxes, causing impaired near vision and photophobia
- It may reduce outflow of aqueous humour, causing increased intramuscular pressure = glaucoma issues
What effect does Atropine have on the skin and mucous membranes?
- Inhibits lacrimal, bronchial, salivary, and sweat gland secretions
- Causes dry mouth, nose, pharynx and bronchi mucous membranes, and hot, dry skin.
What effect does Atropine have on the respiratory system?
- Causes bronchial smooth muscle relaxation (less effective than adrenaline, so not used in asthma)
What effect does Atropine have on the cardiovascular system?
- In low doses, it causes paradoxical bradycardia due to central action similar to vagal activity
- In larger doses, it blocks vagal stimulation on SA node and at the AV junction, causing increased HR
- It has little to no effect on BP as most vascular beds lack significant cholinergic innervation
What effect does Atropine have on the GIT?
- In larger doses, it causes incomplete GIT motility inhibition and a slight reduction in gastric secretions
What effect does Atropine have on the urinary system?
- Slight relaxation of urinary tract smooth muscle +
- Decreased urinary fundus tone +
- Constriction of internal sphincter
= urinary retention, particularly in elderly men with prostatic enlargement
What effect does Atropine have on the CNS?
- In large doses, central muscarinic receptors are blocked to cause excitement, agitation, irritability, hallucinations, delirious, and finally stupor and coma.
- Increase in temperature due to sweating suppression
What are the 4 indications for Atropine, and what is the desired effect?
- C7: Bradycardia. Blocks the effect of vagal stimulation on the SA node and AV junction to increase HR
- E6: Envenomation (symptomatic funnel web spider bite). Reverses SLUDGEM by inhibiting secretions.
- D2: Organophosphate poisoning. Reverses SLUDGEM by inhibiting secretions.
- D5 - Nerve agent poisoning - Reverses SLUDGEM by inhibiting secretions
What are the 8 adverse effects of Atropine, and how are they caused?
- Dry mouth (inhibits muscarinic receptors in salivary glands, reducing salivation)
- Blurred vision (pupil dilation and ciliary muscle relaxation causing impaired near vision)
- Tachycardia (blocks the effects of vagal stimulation on SA node and AV junction = ^HR)
- Nausea and vomiting (blocks receptors in GIT, decreasing gastric motility and gastric secretion)
- Hyperthermia (blocks sweat production = increased temp)
- Dysrhythmias (blocks effects of vagal stimulation on SA node and AV junction = ^HR)
- Agitation, delirium, hallucinations, seizure and coma in high doses (prominent CNS effect due to blocking of central muscarinic receptors)
- Urinary retention (relaxation of urinary tract smooth muscle, decreased tone of urinary bladder fundus, increased constriction of internal sphincter = urinary retention)
What are the contraindications of Atropine?
None.
What are the preparations of Atropine?
- 600mcg in 1mL polyampoule
- 600mcg in 1mL polyampoule dilated to 6mL with 5mL sodium chloride 0.9% (100mcg:1mL)
- 2mg in Atropen Auto-injector
