Review of Pharmacology - 9E (2015)

Anaesthesia
49. Ans. (b) Meprobamate (Ref: Goodman and Gilman 11/e p422)
Meprobamate was used as a CNS depressant drug but is rarely indicated now due to its addictive properties. It is a metabolite
of carisoprodol, which is used as a centrally acting skeletal muscle relaxant.
50. Ans. (a) Atracurium (Ref: Katzung 11/e p453)
Atracurium is eliminated by Hoffman’s elimination i.e. it does not require liver or kidney. It is the muscle relaxant of
choice in hepatic and renal failure.
51. Ans. (a) Azathioprine (Ref: Harrison 17/e p2677, Ajay yadav 2/e p94)
• ‘Azathioprine is used for treatment of myasthenia gravis’
Drugs that may exacerbate myasthenia gravis and potentiate the action of non-depolarizing muscle relaxants are:
• Antibiotics
––
Aminoglycosides e.g Streptomycin
––
Tetracyclines
––
Quinolones e.g ciprofloxacin
––
Macrolides e.g erythromycin
• Non-depolarizing muscle relaxants e.g d-Tubocurarine
• Beta-blockers like propanolol, atenolol, metoprolol
• Local anaesthetics
• Botulinum toxin
• Quinine derivatives like quinine, quinidine, chloroquine, mefloquine
• Magnesium
• Penicillamine
52. Ans. (b) Rapacuronium (Ref: Miller’s anaesthesia 5/e p892; Drugs and equipment in Anaesthesia 5/e p78 Arun Kumar Paul)
• Among the given options Rapacuronium is the shortest acting drug.
• Rapacuronium has been withdrawn from the market because it produces intense bronchospasm in a significant number
of patients.
• Mivacurium is shortest acting NDMR.
• SCh is shortest acting muscle relaxant.
53. Ans. (a) Inhibiting nicotinic receptors at myoneural junction (Ref: Katzung 10/e p429; KDT 6/e p342)
D-tubocurarine is a skeletal muscle relaxant that acts by competitive inhibition of NM receptors at neuron-muscular junction.
54. Ans. (a) Cis-atracurium (Ref: Katzung 9/e p432;KDT 6/e p345)
Atracurium and cis-atracurium are muscle relaxants of choice for renal and hepatic failure patients.
55. Ans. (b) Preventing the K + efflux from the cell (Ref: Katzung 10/e p436;KDT 6/e p99-101)
Neostigmine is an anti-cholinesterase. It inhibits the breakdown of ACh at the motor end plate. This results in the increased
activity of ACh that causes depolarization of motor end plate by opening Na + channels (increasing the influx of Na + ). It
possesses some direct agonistic activity on NM receptors resulting in depolarization. In addition, a minor effect to increase
the release of ACh at motor end plate is also present.
56. Ans. (b) Succinylcholine (Ref: KDT 6/e p343, 344)
General Anaesthesia Pharmacology
• Succinylcholine is a depolarizing neuromuscular blocker. In contrast to ganglionic blocking properties of
competitive neuromuscular blockers (like d-TC), it stimulates the ganglia.
• Initially bradycardia is seen due to stimulation of parasympathetic ganglion which is followed by tachycardia
and hypertension due to stimulation of sympathetic ganglia.
• Dopamine and isoprenaline possess b1 agonistic activity and thus can cause tachycardia.
• Midazolam is a benzodiazepine. It does not affect CVS at therapeutic dose but produces bradycardia at toxic
levels.
57. Ans. (a) Chloroform; (d) Halothane (Ref: Lee 12/e p167, KDT 6/e p372; Ajay yadav 2/e p61,66)
• Masive liver necrosis following halothane anaesthesia is seen in some cases.
• N 2
O is nontoxic to liver, kidney and brain.
• Ether doesnot sensitize the heart to Adr and is not hepatotoxic.
• Enflurane is eliminated mostly via the lungs, although about 3% is metabolised in body and resultant fluoride ions
are excreted by kidney. Hepatic necrosis is seen in very rare instances. (Lee/165)
• If chloroform is given for long period, liver damage occurs (Parikh 5/e p877)
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