Lecture 20- Principles Of Antimicrobial Therapetuics I

Question 1

Antimicrobial therapy warranted for a patient?

Answer 1

Questions on slide 2-3

Question 2

Presumptive (empirical) antimicrobial therapy

Answer 2

Use of antimicrobial agents before the pathogen responsible for a particular illness/susceptibility to a particular antimicrobial agent = empirical / presumptive therapy

Pathogenic organism responsible for illness identified= empiric therapy is usually modified to definitive therapy - narrower in coverage

Slide 4

Question 3

Approach to empirical therapy

Answer 3

Initiation of empiric therapy- follows a specific + systematic approach;

1. Formulate a clinical diagnosis of microbial infection
2. Obtain specimens for laboratory examination
3. Formulate a microbiologic diagnosis
4. Determine the necessity for empiric therapy
5. Institute treatment

Question 4

Choice of antimicrobial agent

Answer 4

Host Factors;
- concomitant disease states, prior adverse drug effects, impaired elimination/detoxification of the drug, age, preg status + epidemiological exposure

Pharmacological Factors;
- kinetics of absorption, distribution + elimination
- ability of the drug to be delivered to site of infection
- potential toxicity of an agent
- pharmacokinetic/pharmacodynamic interaction with other drugs

Knowledge of the susceptibility of an organism

Question 5

Antimicrobial pharmacodynamics

Answer 5

Factors include;
- pathogen susceptibility testing
- drug bactericidal versus bacteria static activity
- drug synergism, antagonism + post-antibiotic affects
+ pharmacokinetics -» selection of optimal antimicrobial dosage regimens

Slide 8

Question 6

Bacteriostatic vs bactericidal activity

Answer 6

Some that are considered to be bacteriostatic could be the opposite against selected organisms

Bacteriostatic + bactericidal agents= equivalent for the treatment of most infectious diseases in immunocompetent hosts

Bactericidal agents= selected over bacteriostatic ones in circumstances - local/systemic host defences are impaired

Bactericidal activity- slide 10

Question 7

Pharmacokinetic factors

Answer 7

Vitro activity= guide as to whether an antibiotic is likely to be effective for an infection

Successful therapy= depends on achieving a drug conc that is sufficient to inhibit/kill bacteria at the site of the infection without harming the pt
Therapeutic goal= several pharmacokinetic + host factors must be evaluated

Question 8

Pharmacokinetic factors

Answer 8

Location of infection- may dictate the choice of drug + route of administration

Infection sited in the cerebrospinal fluid (CSF) = drug must pass the blood-brain barrier

Oral administration is preferred bc of cost + fewer complications than parenteral therapy

Parenteral administration is preferred;
- ill pts= predictable conc of drugs must be achieved
- pts with bacterial meningitis/ endocarditis
- pts with nausea, vomiting, gastrectomy/ diseases that impair oral absorption
- antimicrobials that are poorly absorbed following oral administration