Test 113  (Pharmacology)

1. The following are true about drugs with a high first-pass effect: 

a. they have low bioavailability

b. they are excreted unchanged by the kidneys

c. their levels in the serum are increased in the presence 
    of hepatic failure

d. they are poorly absorbed 

e. they have a high extraction ratio

Answera.T  b.F  c.T  d.F  e.T
Drugs with high first-pass effect are extensively metabolised in the gut and liver and hence low serum bioavailability. Their levels increase in the presence of poor liver function.
 

2. The blood brain barrier is readily permeable to:

a. strong acids

b. weak bases

c. highly water-soluble drugs

d. lipophilic drugs

e. adrenaline

Answera.F   b.T   c.F  d.T  e.F
The blood brain barrier is more permeable to lipid than water soluble drugs. The pH of CSF is about 7.4 and this favours weak bases over strong acids. Adrenaline penetrates the blood brain barrier poorly.

 
3. The following are true about tetracycline:

a. its absorption is reduced by food

b. it should be avoided in patient with renal failure

c. it is extensively metabolised by the liver

d. it reduces the efficacy of oral contraceptives 
   
e. it reduces the anti-coagulant effect of warfarin

Answera.T   b.T  c.F  d.T  e.F
Tetracycline is not extensively metabolised. In the presence of renal failure, it accumulates readily and therefore should be avoided (doxycycline is a safer option). Its absorption is retarded by food and calcium. 
It enhances the anti-coagulant effect of warfarin.
.

4. Ketoconazole:

a. can be used both systemically and topically

b. blocks the demethylation of lanosterol to ergosterol 
    in fungal cells

c. causes renal toxicity

d. inhibits P450 enzymes

e. inhibits the synthesis of steroid enzyme in human at 
    high doses

Answera.T  b.T  c.F  d.T  e.T
Ketoconazole can be either fungistatic or fungacidal depending on doses.  It causes hepatic toxicity rather than renal toxicity.

5. Retinopathy occurs with the following drugs:

a. desferrioxamine

b. vigabatrin

c. ethambutol

d. amiodarone

e. tacrolimus
 

Answera.T   b.T  c.F  d.F  e.T
Ethambutol causes optic neuropathy and amiodarone causes vortex keratopathy and cataract (usually visually insignificant).

 
 

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