Erdman - Polymyxins

Question 1

What is the structure of polymyxins?

Answer 1

Polymyxins are cationic cyclic decapeptides linked to a fatty acid chain by an alpha-amide linkage

Question 2

Polymyxin mechanism of action

Answer 2

Polymyxins are cationic detergents that bind to anionic lipopolysaccharide molecules in the outer cell membrane of gram-negative bacteria causing displacement of Ca and Mg inducing a change in permeability and leakage of cellular contents, leading to cell death

Question 3

What kind of antibacterial effects do polymyxins have?

Answer 3

Concentration-dependent bactericidal activity

Question 4

What are the polymyxins?

Answer 4

-Polymyxin B
-Colistin

Question 5

Mechanisms of resistance for polymyxins

Answer 5

-Alteration of outer cell membrane
-Cross-resistance is observed

Question 6

Polymyxin spectrum of activity against gram-negatives

Answer 6

-Aerobic bacilli only
-PEEACKSSS
-Acinetobacter spp.
-Pseudomonas
-Not active against proteus, providencia, serratia

Question 7

What dosage form are polymyxins?

Answer 7

Only available IV in the US

Question 8

Polymyxin distribution

Answer 8

-Poorly distributed
-About 5% of colistin in CSF

Question 9

Which polymyxin requires dosage adjustment in renal insufficiency?

Answer 9

CMS

Question 10

Polymyxin clinical uses

Answer 10

Infections due to multidrug resistant gram-negative bacteria such as acinetobacter baumanii and pseudomonas

Question 11

Polymyxin adverse effects

Answer 11

-Nephrotoxicity (colistin)
-Neurotoxicity

Question 12

What weight should you use when calculating CMS dose?

Answer 12

IBW

Question 13

What weight should you use when calculating polymyxin dose?

Answer 13

TBW