Test 44    (pharmacology)

1. The following are true with regard to lignocaine:

a. it lowers the threshold of patients for convulsion

b. it can augment bradycardia by augmenting vagal tone

c. it may cause hypotension

d. it slows the heart by producing beta-adrenoceptor blockade

e. it is effective in the treatment of ventricular arrhythmias

Answera.T   b.F   c.T   d.F   e.T
It has no effect on adrenoceptors. In high plasma concentration, it can cause myocardial depression and therefore hypotension. It can be used in the treatment of ventricular arrhythmias.

2. With regard to gentamicin:

a. it is metabolized and excreted mainly by the liver

b. it is well absorbed by the small intestine

c. it can produce permanent vestibular nerve damage

d. it is toxic to the retina

e. topical application is associated with punctate keratitis

Answera.F   b.F   c.T   d.T   e.T
It is excreted mainly by the kidney and therefore should be given with care in patients with renal failure. 

3. The following give rise to non-depolarising blockade of the neuromuscular 
     junction during anaesthesia:

a. succinylcholine

b. physostigmine

c. pancuronium

d. tubocurarine

e. atropine

Answera.F   b.F   c.T   d.T   e.F
Suxamethonium causes a depolarizing blockade.
Physostigmine is an anticholinesterase which can reverse competitive neuromuscular blockade by increasing the concentration of acetylcholine at the neuromuscular junction.
Atropine is an anti-muscarinic drug and does not act at nicotinic acetylcholine receptors found at the muscular junction.

4. The following are true with regard to drug metabolism:

a. lipid-soluble beta-antagonists cause bad dreams more often 
    than water-soluble beta-antagonists

b. a highly plasma protein bound drugs have a very large 
    volume of distribution

c. hepatic drug metabolism often involves conversion of a 
    water-soluble into a more lipid-soluble drug

d. gastrointestinal absorption of lipid soluble drugs occurs 
    more readily than water soluble drugs

e. renal failure significantly increases the plasma 
    protein binding of drugs

Answera.T   b.F   b.F   d.T   e.F
Lipid soluble drugs enters the blood brain barriers more readily and therefore have more central nervous system side effects.
A highly plasma protein binding drug stays in the vascular component and therefore has a volume of distribution of about 4-5 litres.
Hepatic drug metabolism often converts a lipid-soluble drug into a water-soluble one.
Renal failure causes decreased plasma protein concentration and therefore less binding for drugs.

5. The administration of histamine in man can produce:

a. bronchodilatation

b. increased gastric acid secretion

c. vasodilation

d. negative chronotropic action

e. reduced secretion of intrinsic factors

Answera.F   b.T   c.T   d.F   e.F
Histamine causes the triple response: wheal, flare and oedema.
The positive chronotropic action results from a direct effect on heart receptors and by baroreceptor reflex due to vasodilatation.