General Principles of Clinical Usage

Question 1

Patient Characteristics

Answer 1

Age - certain drugs are contraindicated in children (e.g. cipro floxacin, since it affects developing cartilage)

Renal Function - Antimicrobial doses will need to be decreased proportional to the degree of renal insufficiency.

Liver Function -
Doses should be decreased in hepatic insufficiency or an alternate drug should be chosen if possible.

Pregnancy -
Some antimicrobials are thought to be mutagenic, teratogenic, or both.
Some are contraindicated as their effect on the unborn foetus is unknown.
Penicillins, cephalosporins and urinary antiseptic nitrofurantoin are safe.

Question 2

Indication for Antimicrobials -

Prophylaxis

Answer 2

Is the administration of antimicrobials to prevent the future occurrence of infection. This is used in cases where a patient is exposed to patients with highly communicable disease or is shortly about to be subjected to surgical procedures associated with high post-operative infection rates (abdominal operations).

Question 3

Monotherapy vs Combination

Answer 3

The simplest approach is generally the best i.e monotherapy.

But combination is sometimes used: to combat mixed infections, for an enhanced effect and to minimise the development of resistant trains to any one agent.

Outcomes of combination are -
Additive
Antagonistic, their combined effect is less than the sum of their individual contributions.
Synergistic, the combined effect is greater than the sum of the individual contributions.