Principles of Clinical Usage

Question 1

Patient characteristics

Answer 1

Age e.g. ciprofloxacin contraindicated in children as it affects developing cartilage
Renal function
Liver function
Pregnancy
- mutagenic
- teratogenic
- unsafe to use e.g. metronidazole, trimethoprim
- safe to use e.g. penicllins, cephalosporins, nitrofurantoin

Question 2

Prophylaxis

Answer 2

Exposure to infected subjects

Prior to surgical procedures

Question 3

Therapy

Answer 3

Antibiotic sensitivity

Monotherapy is generally best

Question 4

Combination therapy

Answer 4

Outcomes: additive, synergistic, antagonistic
Covers mixed infection
Minimises development of resistant strains (especially in TB and HIV)
Synergistic e.g. penicillin+gentamicin in treatment of streptococcal infective endocarditis (penicillin breaks down cell wall and allows gentamicin to reach the ribosome)

Question 5

Penetration to site of infection

Answer 5

Essential

Question 6

Monitoring

Answer 6

Drugs with low therapeutic index
To ensure therapeutic levels are achieved
To prevent toxicity
Most commonly monitored: gentamicin, vancomycin

Question 7

Dose and duration

Answer 7

Standard course = 7 days
Osteomyelitis/endocarditis = several weeks
S. aureus bacteraemia = at least 14 days of IV
UTI = 3 days trimethoprim
Consult formularies/expert opinion