Antimicrobial PK/PD

Question 1

Cmax

Answer 1

immediately after the infusion

Question 2

Peak

Answer 2

occurs after the C max and is considered post distribution

Question 3

Beta Lactam pharmacofynamics (penicillins, cephalosporins, carbapenems, monobactams)

Answer 3

• outcomes are measured by time of free drug concentration over MIC
• time dependent bactericidal activity (slow activity) (concentration dependent up to 4x MIC which is max)
• short to no post antibiotics effectst for gram negative antibiotics

Question 4

Strategy for Dosing beta-lactam antibiotics

Answer 4

Maximize free drug/MIC as a % of dosing interval

• gram-negatives: carbapenems greater than or equal to 40%, penicillins greater than or equal to 50%, cephalosporins greater than or equal to 60% (longer in critically ill patients)
• gram positive greater than or equal to 40 to 50%
• increase dose, same interval, same dose shorter interval, continuous or prolonged infusions

Question 5

Fluoroquinolone pharmacodynamics (Ciprofloxacin, Levofloxacin, moxifloxacin)

Answer 5

• free AUC/MIC ratio
• rapidly bactericidal, concentration dependent bactericidal activity
• postantibiotic effect for both gram negative an d gram positive bacteria
• free AUC 100 for gram negative, gram positive use 100 because although 30-40 may be efficacious there is a greater risk of resistance

Question 6

Aminoglycosides pharmacodynamics

Answer 6

• correlation with Peak to MIC ratio 8-10:1
• rapidly bacterialcidal, post antibiotic effect for gram negative and gram positives
• adapticve resistace, (transport into the cell requires ATP and oxygen so less useful in anaerobes) occurs when consistent levels of drug are present so that is why we want there to be a drug free interval. pump downregulation

Question 7

Vancomycin Pharmacodynamic bacteria

Answer 7

• time dependent bactericidal activity, very long PAE For gram positive organisms. Goal outcome is AUC24HR/MIC of 400-600. time dependent bacteridial agent