Test 47 (pharmacology)

1. Warfarin:

a. the effect of anticoagulation occurs within the first 48 hours
    after the first dose

b. has a half-life of about 12 hours

c. its action is terminated through hepatic metabolism

d. is well absorbed from the gastrointestinal system

e. its action is potentiated by concurrent use of cimetidine

Answera.F   b.F   c.T   d.T   e.T
Its effect only become obvious 72 hours after the first does. 
This is because the clotting factors present in the circulation needs to be eliminated first. 
The half-life of warfarin is 36 hours
Cimetidine inhibits the enzymes that metabolizes warfarin

2. 5-fluorouracil:

a. causes megaloblastic anaemia

b. is more effective than mitomycin in reducing fibrosis

c. inhibits thymidylate synthetase

d. is excreted mainly by the renal system

e. is used in the treatment of bowel carcinoma

Answera.T   b.F   c.T   d.F   e.T
Mitomycin kills off the fibroblast whereas 5-fluorouracil only inhibits the fibroblast proliferation.
Only 20% of the 5-fluorouracil is excreted by the urine, the rest is metabolized by the liver.

3. Cefuroxime:

a. inhibits cell wall synthesis

b. has cross-sensitivity with penicillin

c. has good CSF penetration

d. is a third generation cephalosporin

e. is less toxic to the corneal epithelium than gentamicin

Answera.T   b.T   c.T   d.F   e.T
It is a second generation cephalosporin
 

4. The following are true about the drugs used in general anaesthetic:

a. suxamethonium causes hyperkalaemia

b. thiopentone is contraindicated in porphyria

c. ketamine increases the sympathetic activity in the nervous 
    system

d. ketamine can reduce the intraocular pressure

e. inhaled isoflurane is mainly metabolized by the liver

Answera.T   b.T   c.T   d.T   e.F
Only a small proportion of the isoflurane (about 0.2%) is excreted by the liver.

5. The following are true about lignocaine:

a. it has a local anaesthetic action lasting for about 6 hours
b. is more active if injected into an inflamed area
c. inhibits the rapid influx of sodium ions into excitable cells
d. its action is prolonged by the concurrent use of adrenaline
e. its onset of action is faster than that of marcaine

Answera.F   b.F   c.T   d.T   e.T
Its action typically lasts for only an hour. Therefore it is often combined with marcaine. The later has the advantage of longer duration of action but its onset of action is slower than lignocaine.
Lignocaine is a weak base and the pH of an inflamed area is usually acidic. Therefore, injection of the lignocaine into an inflamed area results in the formation of more ionised forms which are less lipid soluble and poorer tissue penetration.