Pharmacokinetics and Antimicrobial Therapy

Question 1

In what 2 ways are antibiotics classified?

Answer 1

Mode of action (bactericidal or bacteriostatic)

Spectrum of action (broad or narrow spectrum)

Question 2

Examples of bactericidal antibiotics?

Answer 2

penicillins
cephalosporins
quinolones

Question 3

What is EC50?

Answer 3

The concentration of drug to get half the maximal response

Question 4

3 key objectives in antibiotics treatment?

Answer 4

1) eradicate the bacteria causing disease symptoms
2) avoid selection and emergence of resistant bacteria
3) reduce drug-induced toxicity

Question 5

Name some host factors in antibiotic effectiveness

Answer 5

Underlying comorbidities
Immune system status
Renal and hepatic function
Concomitant drug use
Age

Question 6

3 major factors in the effectiveness of antibiotics?

Answer 6

1) spectrum of activity (has to have appropriate spectrum of activity - not unnecessarily broad spectrum, not too narrow)
2) sensitivity (have to know if the bacteria is sensitive to the antibiotic)
3) PK properties

Question 7

What is the MIC and what does it mean?

Answer 7

Minimum Inhibitory Concentration - the minimum concentration of drug required to stop the growth of bacteria

Question 8

What is the PAE and what does it mean?

Answer 8

Post-antibiotic effect - shows if the drug has persistent action after drug concentration falls below the MIC

Question 9

What is the MBC and what does it mean?

Answer 9

Minimum bactericidal concentration - the minimum concentration of drug required to kill bacteria

Question 10

How do we tell if a drug is bacteriostatic or bactericidal?

Answer 10

Find the MIC and the MBC. If the MIC is the same as MBC = bactericidal. If the MBC is greater than the MIC = bacteriostatic

Question 11

Classification of antibiotics on their PK-PD properties - what are the 3 classifications? Give examples of antibiotics and list the indicators for each

Answer 11

Class 1 Time-dependent:

• beta lactams, vancomycin
• T > MIC (time above MIC)

Class 2 Concentration dependent:

• aminoglycosides, quinolones
• AUC > MIC
• Cmax : MIC

Class 3 Mixed

• macrolides, tetracycline
• AUC : MIC

Question 12

How are PK-PD models used to determine drug administration?

Answer 12

Find out which class the antibiotic fits into
(by plotting the indicators by the bacterial burden and finding which has the strongest relationship)

Time dependent: slow injection
Concentration dependent: bolus injection
Mixed: in between

Question 13

How are PK-PD models used to minimise resistance?

Answer 13

Give doses above the MPC (mutant prevention concentration - the MIC of the most resistant strain within the population). This means that all bacteria will be susceptible to the antibiotic.

Question 14

What does the use of bacteriostatic antibiotic require from the host?

Answer 14

A functioning immune system - BS antibiotics only inhibit bacterial growth, and the bacteria die after they’re normal lifespan. It requires the immune system to help with eradication