Pharmacology

Question 1

Ceftriaxone?

Answer 1

• High binding to albumin
• Needs to be given as continuous infusion
• Concentration require to be above MIC
• It can be given once a day as free fraction is released slowly from albumin

Question 2

Digoxin for AF ?

Answer 2

Not the first choice of drug as it can induce ventricular arrhythmia.

Question 3

Isoprenaline?

Answer 3

Acts mostly on B1 & B2 receptors.

Question 4

What is pharmacokinetics ? Components?

Answer 4

This is what the body does to the drugs

• Absorption
• Distribution
• Metabolism
• Excretion / Elimination

Question 5

What is pharmacodynamics?

Answer 5

This what the drug does to the body e.g; MIC of bacteria

Question 6

Consideration of antibiotics? Components?

Answer 6

• Drug
• Bug
• Patient

Question 7

Patient factors affecting antibiotics?

Answer 7

• Organ perfusion
• Volume of distribution
• Clearance

Question 8

Factors affecting pharmacokinetics of drugs ?

Answer 8

• Low albumin
• Altered volume of distribution
• Augmented renal clearance

Question 9

Augmented renal clearance occurs in ?

Answer 9

• Young trauma patients
• Burns
• Sepsis

Question 10

Antibiotics modes of action?

Answer 10

• Cell wall ( Beta-lactam, Vancomycin)
• DNA/RNA synthesis (Fluoroquinolones, Rifamycins)
• Folate synthesis (Trimethoprim, Sulfonamides)
• Cell membrane (Daptomycin)
• Protein synthesis ( Linezolid, Tetracycline, Macrolides & Aminoglycosides)

Question 11

Mechanisms of antibiotic resistance ?

Answer 11

• Efflux (Fluoroquinolones, Aminoglycosides, Tetracyclines, B-lactams & Macrolides)
• Immunity & bypass (Tetracycline, Trimethoprim, Sulfonamides, Vancomycin)
• Target modification ( Fluoroquinolones, Rifamycins, Vancomycin, Penicillin, Macrolides & Aminoglycosides)
• Inactivating enzymes (B-lactams, Aminoglycosides, Macrolides & Rifamycins)

Question 12

MIC? Minimal inhibitory concentration

Answer 12

This is the concentration at which there is no more growth of bacteria. Relates to Pharmacodynamics

Question 13

Examples of Beta-lactam antibiotics?

Answer 13

• Penicillins
• Cephalosporins
• Carbapenems

Question 14

Mechanism of action of antibiotics in relation to MIC ?

Answer 14

• Work by time above MIC (Beta-lactam)

- Work by peak divided by MIC (ex. Gentamicin)

Question 14

Mechanism of action of antibiotics in relation to MIC ?

Answer 14

• Work by time above MIC (Beta-lactam)
• Work by (concentration) peak divided by MIC (ex. Gentamicin) - i.e peak above MIC ratio
• Concentration & time dependent (AUC/MIC)

Question 15

Resistant bacteria in relation to MIC?

Answer 15

• MIC is higher in resistant bugs

- At least 4 times the MIC

Question 16

Antibiotics - Time dependent ?

Answer 16

• Bata-lactam
• Carbapenem
• Linezolid

Question 17

Antibiotics - Concentration dependent?

Answer 17

• Aminoglycosides
• Metronidazole
• Fluoroquinolones

Question 18

Antibiotics - Time & Concentration dependent ? AUC:MIC

Answer 18

• Fluoroquinolones
• Aminoglycosides
• Glycopeptides (Vancomycin)
• Tigecycline

Question 19

Antibiotics according to duration above MIC?

Answer 19

Carbapenems < Penicillin < Cephalosporins

Thus cephalosporins is the longest in time above MIC and Carbapenems shorter

Question 20

Antibiotics according to duration above MIC?

Answer 20

Carbapenems < Penicillin < Cephalosporins

Thus cephalosporins is the longest in time above MIC and Carbapenems shorter

Question 21

Measurement of peak levels of antibiotics is for ?

Answer 21

Efficacy

Question 22

Measurement of trough levels of antibiotics is for ?

Answer 22

Toxicity

Question 23

What are the determinants of Pharmacokinetics?

Answer 23

• MW
• Lipid solubility
• Protein binding
• Elimination pathways

Question 24

Factors affect pharmacokinetics of drugs ?

Answer 24

- Clearance - Volume of distribution - Half life - Cmax - Cmin - AUC (0-24)

Question 25

What is clearance?

Answer 25

Volume of blood cleared of the drug per unit time

Question 26

What is volume of distribution?

Answer 26

The apparent volume of fluid that contains the total drug dose administered at the same concentration as in the plasma.

Question 27

What is half-life?

Answer 27

This is the time required for plasma drug concentration to decrease by half

Question 28

What antibiotics are concentration dependent? Cmax/MIC

Answer 28

- Aminoglycosides - Metronidazole - Fluoroquinolones

Question 29

Antibioitcs which are concentration dependent with time dependent? AUC24/MIC

Answer 29

- Fluoroquinolones - Azithromycin - Tetracyclines - Glycopeptides

Question 30

Time dependent antibiotics T > MIC

Answer 30

- Beta-lactams - Carbapenems - Linezolid - Erythromycin - Clarithromycin - Clindamycin

Question 31

List hydrophilic antimicrobials?

Answer 31

- Aminoglycoside - Beta-lactam (Carbapenem, Cephalosporins, Penicillin) - Glycopeptides - Lipopeptides

Question 32

List of lipophilic antimicrobials?

Answer 32

- Fluoroquinolones - Ketolides - Lincosamides - Macrolides - Metronidazole - Streptogramins - Tetracycline

Question 33

DIstribution and clearance of lipophilic antimicrobials?

Answer 33

- Tissue distribution limited to extracellular space - Renal clearance - In sepsis - Need for increased loading dose / Need for increased or decreased maintenance dose

Question 34

Distribution and clearance of lipophilic antimicrobials ?

Answer 34

- Tissue distribution with intracellular accumulation - Hepatic clearance - In sepsis - No need for increased Loading dose and maiintenance dose adjustment