Test 187  (Pharmacology)

1. Hypokalaemia occurs with the following drugs:

a. foscarnet

b. aciclovir

c. amphotericin B

d. carbonic anhydrase inhibitors 

e. itraconazole

 
Answera.T   b.F  c.T   d.T  e.T

2. Tetracycline:

a. directly inhibits DNA synthesis in bacteria

b. crosses the placenta and accumulates in foetal skeleton

c. is useful in corneal melt because it has anticollagenase 
    properties

d. is absorbed mainly through the stomach

e. has longer half lives than doxycycline

 

Answera.F  b.T  c.T  d.F  e.F
Tetracycline binds to 30S ribosomes and inhibits protein synthesis. It is bacteriastatic. It is absorbed mainly through the proximal small bowels. Its half-lives is about 8 hours compared with its analogue such as minocycline or doxycycline which have a half-lives of 16 to 18 hours.

 
 

3. The following pupils can be constricted with 1% pilocarpine:
 

a. Adie's pupil

b. Horner's pupil

c. Complete third nerve palsy

d. Argyll-Robertson's pupil

e. Marcus-Gunn pupil

 
Answer
a.T   b.T  c.T  d.T  e.T
Pilocarpine is a directly acting muscarinic agent. In the conditions listed above, the receptors are intact and not occupied as  in atropine-induced mydriasis and therefore responsive to 1% pilocarpine

 

. 4. The following drugs affect the pupil size without affecting the 
      accommodation of the lens:

a. phenylepherine

b. tropicamide

c. ecothiopate

d. thymoxamine

e. cocaine

Answer
a.T  b.F  c.F  d.T  e.F
Phenylepherine is a sympathomimetic and thymoxaine is an alpha adrenergic antagonists. They do not appear to affect lens accommodation. Tropicamide is an anticholinergic inhibitor and causes cycloplegia. Ecothiopate is an irreversible cholinesterase inhibitor and increases accommodation. Cocaine has partial cycloplegic effect.

5. Thymoxamine:

a. can be used to reverse mydriasis caused by 
    phenylepherine

b. causes transient hyperaemia of the conjunctiva

c. causes miosis in normal people and decreased
    intraocular pressure

d. causes lid retraction in normal population

e. can be used to differentiate angle-closure glaucoma 
    from open-angle glaucoma

 
Answer
a.T   b.T  c.F  d.F  e.T
Thymoxamine is an alpha adrenergic blocking agent which works by competitive antagonism of noradrenaline. It causes miosis but does not affect the ciliary muscle or the intraocular pressure in normal population. It can be used to reverse mydriasis caused by phenylepherine, lower eyelid in lid retraction due to thyroid ophthalmopathy and differentiate angle-closure glaucoma from open-angle glaucoma. A reduction of intraocular pressure with topical thymoxamine suggests angle-closure glaucoma whereas normal or minimally reduced intraocular pressure suggests open-angle glaucoma.

 

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