Test 132  (Pharmacology)

1.  Acyclovir:

a. is a guanine derivative

b. is active against all viruses within the herpes family

c. inhibits RNA gyrase

d. is activated by thymidine kinase within the host cells

e. is more effective against herpes simplex keratitis 
    if given orally than topically
 

Answer
a.T   b.F   c.F   d.F   e.F
Acyclovir is activated by viral thymidine kinase and 
acts by inhibiting DNA polymerase. It is not effective 
against cytomegalovirus. Both topical oral acyclovir are effective against herpes simplex keratitis. Oral acyclovir is recommended if the patients is immunosuppressed.

2. Ganclovir:

a. is toxic to kidney

b. causes bone marrow failure

c. is effective against systemic cytomegalovirus infection
    if given orally

d. can be given intravitreally for refractory 
    cytomegalovirus retinitis

e. inhibits DNA polymerase
 

Answer
a.T   b.T   c.F   d.T   e.T
Ganclovir is only effective against systemic cytomegalovirus infection if given intravenously. 

3. Aminoglycosides:

a. are effective against streptococci

b. require aerobic transport mechanisms to enter 
    the bacterial wall

c. act on messenger RNA

d. are not effectively against systemic infection if
    given orally

e. cause retinal necrosis with intravitreal injection
 

Answer
a.F   b.T   c.T   d.T   e.T
Aminoglycosides require aerobic transport mechanisms to enter the bacterial cell. Therefore, not effective 
against Streptococcus and strict anaerobes which have not oxidative transport mechanisms.

4. Chloramphenicol:

a. inhibits cell wall synthesis

b. is active against Haemophilus and Neisseria

c. causes ototoxicity

d. causes aplastic anaemia

e. of the topical form should not be given to children 
    under 10 years of age
 

Answer
a.F   b.T  c.F   d.T   e.F
Chloramphenicol inhibits peptidyl-transferase. 
Its main side effect is aplastic anaemia but this 
complication is very rare with topical form. 
Ototoxicity is a feature of aminoglycosides.

5. Sulphonamides:

a. inhibit the conversion of para-aminobenzoic acid 
    to folate.

b. are bactericidal

c. are slow-acting 

d. can cause folate deficiency if taken for more than 
    two months

e. are a known cause of  Steven-Johnson's syndrome
 

Answer
a.T   b.F  c.T  d.F   e.T
Sulphonamides are bacteristatic and slow-acting
as it takes several generation of bacteria to deplete
the folate pool. The host cells do not produce folate and therefore not affected by the drugs.

 

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