Review of Pharmacology - 9E (2015)

Review of Pharmacology
Explanations
Autonomic Nervous System
1. Ans. (d) Partial heart block (Ref: KDT 7/e p108-110)
• Cholinergic drugs decrease the conduction from atrium to ventricle , thus should be avoided in partial heart block
• Cholinergic drugs like pilocarpine and physostigmine are used in angle closure glaucoma
• Neostigmine (acetylcholineesterase inhibitor, a cholinergic drug) is used for treatment of myasthenia gravis
• Neostigmine is also used for post operative paralytic ileus and post operative urinary retention.
2. Ans. (a) Brimonidine: Decrease aqueous production (Ref: KDT 7/e p154)
Drug: Mechanism of action in glaucoma
Apraclonidine/Brimonidine Stimulate: post-synaptic alpha 2 receptors and result in decreased aqueous production
Latanoprost: Increase uveoscleral outflow
Miotics (Pilocarpine): Increase trabecular outflow
Beta blockers (Timolol/betaxolol): Decrease aqueous production
Carbonic anhydrase inhibitors (acetazolamide): Decrease aqueous secretion.
3. Ans. (b) Bradycardia (Ref: KDT 6/e p104)
Cholinomimetic drug will cause bradycardia as an adverse effect and thus cannot be used for its treatment.
4. Ans. (a) Organophospahte poisoning (Ref: Katzung 12/e p110)
These are characteristic features of anti-cholinestearse (organophosphate and carbamate) poisoning.
Features of Organophosphate poisoning:
• Muscarinic symptoms: Pin point pupil, salivation, lacrimation, urination, defecation, gastrointestinal distress, vomiting,
bronchospasm, bradycardia
• Nicotinic symptoms: Fasciculations and fibrillations of muscle, tachycardia, tachypnea
• CNS symptoms: Temors, giddiness, ataxia, coma
• Red tears: Due to accumulation of porphyrin in the lacrimal glands
5. Ans. (d) Apraclonidine (Ref: Drug Facts and Comparisons 2006/2257)
Apraclonidine is a sympathomimetic agent used in open angle glaucoma. It decreases aqueous secretion. It can result in
upper lid retraction as an adverse effect. It can also result in ocular allergy (less likely with brimonidine). Both apraclonidine
and brimonidine can cause CNS depression and apnea in neonates and are contra-indicated in children less than 2
years of age.
6. Ans. (d) Pharmacological block (Ref: Goodman and Gilman 12/e p1777)
looking at the options one by one:
• Diabetic 3rd nerve palsy: Third nerve palsy due to any reason will result in mydriasis (because oculomotor
nerve supplies constrictor pupillae). However, as only nerve supply is destroyed but the receptors remain
intact, so it will respond to pilocarpine (1%) and thus miosis will occur.
• Adie’s tonic pupil: It manifests as denervation supersensitivity. Normal pupil responds to 1% Pilocarpine but
does not contract with highly diluted solution like 0.05-0.1%. However, in Adie’s pupil due to supersensitivity
of receptors, even this diluted solution may also result in constriction.
• Uncal herniation: It result in pressure on third cranial nerve and presents as dilated pupil but it will respond
to Pilocarpine as the receptors are intact.
• Pharmacological block: Drugs like atropine block the muscarinic receptors present on the pupil. As the
receptors cannot work, even high doses of Pilocarpine cannot produce miosis.
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7. Ans. (b) Postganglionic sympathetic from cervical sympathetic chain (Ref: Ganong 23/e p261, 265)
Constrictor pupillae (circular muscle of iris) is supplied by postganglionic parasympathetic fibres from Edinger Westphal
nucleus whereas dilator pupillae (radial muscle of iris) is supplied by sympathetic fibres of cervical sympathetic chain.
8. Ans (b) Trochlear (Ref: Katzung 11/e p78)
Parasympathetic cranial nerves are III (oculomotor), VII (facial), IX (glossopharyngeal) and X (vagus).
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