Paper I
2022 May (Supplementary) (2010 Scheme) · 40 marks · 120 min

Question

Classify atropine substitutes, explain their uses and adverse effects (3+2+1)

Q16 marksEssays

Answer

Classification of atropine substitutes

BasisGroupExamples
Duration/CNS penetrationNo CNS penetration (quaternary)Glycopyrrolate, Ipratropium/Tiotropium
Marked CNS actionHyoscine (scopolamine)
SelectivityOphthalmic (mydriatic/cycloplegic)Tropicamide, Homatropine, Cyclopentolate
Antispasmodic (GI/urinary)Dicyclomine, Oxybutynin, Tolterodine
BronchodilatorIpratropium, Tiotropium

Uses

  • Glycopyrrolate — pre-anesthetic medication and reversal of neuromuscular-blocker-associated bradycardia (no CNS effects, longer action than atropine)
  • Ipratropium/Tiotropium — inhaled bronchodilation in asthma/COPD
  • Hyoscine — motion sickness, antisecretory pre-anesthetic sedation
  • Tropicamide/Homatropine — short-acting mydriasis/cycloplegia for ophthalmic examination
  • Dicyclomine — antispasmodic in infantile colic/IBS
  • Oxybutynin/Tolterodine — overactive bladder

Adverse effects

  • Dry mouth, blurred vision, constipation, urinary retention (shared antimuscarinic profile, milder than atropine because of peripheral selectivity/quaternary structure limiting systemic spread)
  • Hyoscine — more prominent sedation/CNS effects than the quaternary agents
  • Tachycardia with higher doses

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