Concentration vs Time Dependent Antibiotics.pptx

A short presentation about the difference in pharmacodynamics of concentration-dependent vs. time dependent antibiotics and the clinical implications of this phenomenon.

1. Optimal Antibiotic Dosing The Pharmcokinetic -Pharmacodynamic Interface Hasan Arafat, M.D Resident Physician, Internal Medicine Augusta Victoria Hospital

2. Introduction Antibiotics can be classified according to their pattern of antimicrobial activity into to classes: Concentration-dependent killing Time-dependent killing Hybrid pattern

3. Introduction Concentration-dependent killing: the higher the drug concentration relative to pathogen MIC, the greater the rate and extent of antimicrobial activity Time-dependent killing: the duration of exposure determines the antimicrobial activity Hybrid pattern: antimicrobial activity is dependent on the duration of exposure with a prolonged, persistent post-antibiotic effect

4. Concentration-Dependent Antibiotics Bactericidal effect is directly proportional to the level of drug Associated with post-antibiotic effect: A phenomenon in which the bactericidal effect of a drug continues for a period of time after the antibiotic level falls below the MIC Efficacy of these antibiotics is determined by the area under the curve (AUC) A concentration of at least 10x MIC is needed for optimal effect

5. Time-Dependent Antibiotics Optimal activity is exerted when drug concentration is maintained above MIC Typically, 2-4x MIC throughout the dosing interval Higher concentration does not result in greater killing No post antibiotic effect

6. MIC

7. AUC

8. C max the highest concentration of drug in the blood that is measured after a dose. C max usually occurs within a few hours after the dose is administered.

9. Pharmacological Indices of Antibiotic Activity Peak/MIC: ratio is defined as the /MIC) peak level divided by the MIC. It is used to predict the efficacy of concentration dependent antibiotics. AUC/MIC is defined as the area under the AUC/MIC curve over 24 hours divided by the MIC2. It is also used to predict the efficacy of concentration-dependent antibiotics. T>MIC is defined as the cumulative T>MIC percentage of time over a 24 hour period that the drug concentration exceeds the MIC2. It is used to predict the efficacy of time dependent antibiotics. Postantibiotic effect defined as persistent suppression effect of bacterial growth after a brief exposure (1-2 h) of bacteria to an antibiotic even in the absence of host defense mechanisms.