Review of Pharmacology - 9E (2015)

Review of Pharmacology
Autonomic Nervous System
22. Ans. (c) It has additional direct agonistic action on nicotinic receptors at muscle end plate (Ref: KDT 6/e p103)
Neostigmine is a quaternary ammonium derivative and is lipid insoluble. Its absorption from GIT and penetration in the
brain and cornea is much less than physostigmine. It produces additional action on N M
receptors.
23. Ans. (b) It is longer acting (Ref: KDT 7/e p108)
• Pyridostigmine acts for 3-6 hours as compared to 0.5-2 hour duration of action of neostigmine.
• It is less potent than neostigmine.
• Rest of the properties are similar to neostigmine.
24. Ans. (a) Shorter duration of action (Ref: KDT 6/e p101)
25. Ans. (d) α 2
Receptors (Ref: KDT 6/e p146)
Stimulation of α 2
receptors located on ciliary epithelium reduces secretion of aqueous humor.
26. Ans. (a) Strong local anaesthetic activity (Ref: KDT 6/e p144)
Timolol and betaxolol are the preferred β-blockers for the treatment of glaucoma because they lack local anaesthetic activity.
Drugs possessing this property increase the risk of corneal ulcers.
27. Ans. (b) Betaxolol (Ref: KDT 6/e p145)
Betaxolol is a cardioselective β-block useful in glaucoma. It is longer acting than timolol. Another non-selective
β-blocker used topically for the treatment of glaucoma is levobunolol.
28. Ans. (b) Cycloplegia (Ref: KDT 6/e p93)
Botulinum toxin interferes with the release of ACh and thus acts as a parasympatholytic agent. Bronchospasm and diarrhoea
are the symptoms of muscarinic stimulation whereas muscle spasms may be seen on nicotinic stimulation. Cholinergic
drugs cause cyclospasm whereas anticholinergics result in cycloplegia.
29. Ans. (c) Pilocarpine (Ref: KDT 6/e p98)
Pilocarpine is a directly acting and physostigmine is an indirectly acting cholinomimetic useful for glaucoma.
30. Ans. (a) Atropine (Ref: KDT 6/e p104)
31. Ans. (c) Organophosphate poisoning (Ref. KDT 6/e p104, 105)
All the symptoms are of anticholinesterase poisoning except raised blood pressure and heart rate. At high doses, ACh can
stimulate N N
and N M
receptors. These symptoms may occur due to the nicotinic actions of ACh.
32. Ans. (c) Muscle paralysis (Ref. KDT 6/e p104, 105)
Atropine is a non-selective antagonist at muscarinic receptors. It can penetrate blood brain barrier and reverse the muscarinic
action in the CNS. It can also reverse hypertension and bronchoconstiction caused due to stimulation of muscarinic
receptors. However, muscle paralysis is due to Nicotinic (N N
) action on which it has no activity.
33. Ans. (d) Postural hypotension (Ref. KDT 6/e p115)
Postural hypotension is due to blockade of sympathetic system. Ganglion blockers inhibit the transmission through both
sympathetic as well as parasympathetic ganglia whereas muscarinic blockers inhibit only parasympathetic activity.
34. Ans. (b) Diarrhea (Ref. KDT 6/e p101)
Neostigmine and pyridostigmine are reversible cholinesterase inhibitors that can cause cholinergic adverse effects like
diarrhoea and increased secretions.
35. Ans. (d) It interferes with the action of acetyl cholinesterase (Ref: Katzung 11/e p105)
Neostigmine acts by inhibiting the enzyme acetylcholinesterase. This enzyme is involved in degradation of ACh, consequently
neostigmine increases the synaptic level of ACh. Muscle weakness can be improved by stimulation of N M
receptors
at muscle end plate due to increased ACh.
36. Ans. (c) Cause muscles to relax and be unable to contract (Ref: KDT 6/e p340)
Drugs competing with Ach at neuromuscular junction are competitive or non-depolarizing neuromuscular blockers. These
drugs are used as muscle relaxants. In contrast to depolarizing muscle relaxants, these donot cause initial fasciculations.
37. Ans. (d) Memantine (Ref: KDT 6/e p472, 473)
• Donepezil, rivastigmine, gallantamine and tacrine are cholinergic (due to inhibition of cholinesterase enzyme) drugs
useful for Alzheimer’s disease.
• Memantine is an NMDA blocker, used for Alzheimer’s disease.
38. Ans. (d) Quarternary structure (Ref: KDT 6/e p101)
Quarternary ammonium compounds are water soluble and thus cannot cross blood brain barrier. Neostigmine is a quarternary
derivative whereas physostigmine is a tertiary amine.
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