Test 110   (Pharmacology)

1. The following are true about local anaesthetics: 

a. they are weak bases

b. they are either aminoesters or aminoamides

c. they act faster on myelinated fibres than 
    non-myelinated nerve fibres

d. they cause both sensory and motor paralysis

e. the potency and duration are increased by increasing 
    the lipophilia of the compounds

Answera.T  b.T  c.F  d.T  e.F
Local anaesthetics act faster on unmyelinated than myelinated fibres.
 

2. The following are true about the local anaesthetics:

a. they are hydrolysed by plasma cholinesterase

b. they are degraded by hepatic enzymes

c. concurrent use of adrenaline increases the duration of action 

d. inadvertent intravascular injection of local anaesthetics can result in respiratory arrest

e. the plasma levels of local anaesthetics are higher in patients taking pilocarpine.

Answera.T   b.T   c.T   d.T  e.F
Aminoesters are mainly inactivated by plasma cholinesterase through hydrolysis whereas aminoamides are mainly degraded through the action of hepatic enzymes. Drugs that interferes with cholinesterase increases the plasma levels of local anaesthetics. These occur with echothiophate.

 
3. The corneal penetration of a topically applied drug:

a. is increased if the epithelium is removed

b. is increased if the intraocular pressure is reduced

c. is increased if the tear production is increased

d. is decreased if the blink rate is increased

e. is decreased if the drug is made more hydrophilic

Answera.T   b.F  c.F  d.T  e.T
Reducing the intraocular pressure does not affect drug penetration of the cornea. Increased tear production dilutes the drug and thus reduces corneal penetration. The cornea penetration is increased if the drug is made more hydrophobic or lipophilic.
.

4. With regard to carbonic anhydrase inhibitors:

a. they inhibit carbonic anhydrase isoenzyme II

b. they have an additive effect when use with beta 
    blockers

c. systemic side effects do not occur with topical carbonic 
    anhydrase inhibitors.

d. topical dorzolamide has a better corneal penetration 
    than topical acetazolamide

e. dorzolamide possess ampholytic character

Answera.T  b.T  c.F  d.T  e.T
Systemic side effects can still occur with topically applied carbonic anhydrase inhibitors. Dorzolamide is lipid soluble at pH 7 and water soluble at pH 5 and 9. At the normal tear pH, its lipophilic character allows it to penetrate the cornea better than acetazolamide.

5. FK 506:

a. is derived from fungus

b. selectively inhibits the function of B cell lymphocytes 

c. decreases antibody production to T-cell dependent 
    antigens

c. is 100 times more potent than cyclosporin A

d. is used in preventing allograft rejection

Answera.T  b.F  c.T  d.T  e.T
Like cyclosporin, FK 506 is derived from the fungus and selectively inhibits T lymphocytes especially T helper cells.
It is 100 times more potent than cyclosporin. 

 
 

More MCQs