Drugs for Skin/Soft tissue Infections

Question 1

Uncomplicated skin and soft tissue infections in immunocompetent persons are most commonly caused by?

Answer 1

Staph aureus and Strep pyogenes

Question 2

Complicated skin infections (e.g. with burns, diabetes, ulcers, etc) are more likely be caused by what?

Answer 2

more commonly polymicrobial and often include anaeobes and gram neg rods, such as E. coli and Pseudomonas

Question 3

What are the drug options for uncomplicated non-MRSA infections?

Answer 3

these are typically susceptible to beta-lactamase resistance penicillins (dicloxacillin, nafcillin, and oxacillin) and 1st-gen cephalosporins (cephalexin, cefazolin)

Question 4

What if a patient with uncomplicated non-MRSA infections has an allergy to a penicillin or cephalosporins?

Answer 4

Clindamycin (50s inhibitor) or Vanco can be used

Question 5

What is the typical allergy to penicillins?

Answer 5

this is typically an IgE-mediated allergy (histamine release causing urticaria, angioedema, anaphylaxis). Remember that historically, patients who are truly allergic to a penicillin would also display symptoms to a 1st or 2nd gene cephalosporin (due to related R1 side chain rather than beta-lactam structure)

Question 6

Again, it is hypothesized that the R1 side chain of both penicillins and cephalosporins is responsible for cross-reactive hypersensitivity. Which drugs possess this adduct?

Answer 6

• penicillin G, ampicillin, amoxicillin
• cefoxitin, cefaclor, cephalexin, cefadroxil, cefprozil

Question 7

Most penicillins are eliminated renally and require dose-adjustment in renal failure, except which drugs?

Answer 7

nafcillin (mostly hepatic and only requires dose adjustment if hepatic AND renal involvment present)

• Oxacillin (hepatic elimination)
• Dicloxacillin (renal elim but no adjustment needed)

Question 8

Does clindamycin require dose adjustment in RF? Vanco? What about cephalosporins

Answer 8

While vanco and cephalosporins DO require dose adjustment in RF, clindamycin is eliminated hepatically and does not

Question 9

What is a common AE for beta-lactams?

Answer 9

Hypersensitivity and GI distress

Question 10

What is another common AE for penicillinase-resistant penicillins (like nafcillin, dicloxacillin, and oxacillin)

Answer 10

interstitial nephritis

Question 11

AEs of vanco?

Answer 11

Red man syndrome and hypotension with rapid IV injection

Nephro (reversible) and ototoxicity

Question 12

What are some illnesses associated with CA-MRSA?

Answer 12

cellulitis, abscesses, necrotizinf fasciitis, and sepsis rarely

Question 13

How would simple CA-MRSA induced abscesses and less serious skin and soft tissue infections be treated?

Question 14

What drug class SHOULD NOT be used empirically to treat MRSA? Why?

Answer 14

Fluoroquinolones due to increasing resistance

Question 15

How does Linezolid work?

Answer 15

Binds to the 23S of the 50S subunit and prevents initiation complex formation with the 70S subunit

Question 16

What are the AEs of Bactrim?

Answer 16

N/V, dyspepsia

photosensitivity

Fetal risk in 1st and 3rd trimester

Question 17

How is Bactrim eliminated?

Answer 17

Renal (dose-adjustment needed)

Question 18

How are the tetracyclines eliminated?

Answer 18

Hepatic and renal (dose adjustment required in RF)

Question 19

AEs of tetracyclines?

Answer 19

• hepatotoxicity
• discolored teeth
• fetal risk
• photosensitivity

Question 20

How is clindmaycin eliminated?

Answer 20

Hepatic (no dose adjustment in LF/RF)

Question 21

AEs of Clinda?

Answer 21

C-difficile infection

• SJS
• jaundice

Question 22

AEs of Linezolid?

Answer 22

• optic neuropathy and vision loss
• serotonin syndrome and seizures
• myelosuppression
• lactic acidosis

Question 23

What causes optic neuropathy with linezolid?

Answer 23

thought to be casued by mitochondrial dysfunction in the optic nerve (reversible upon discontinuing the drug)

Question 24

What is serotonin syndrome?

Answer 24

mental status changes and autonomic hyperactivity caused by excessive levels of serotonin (that is a common effect of co-administration of serotonin increasing drugs such as isoniazid, linezolid, and SSRIs for depression)

Question 25

How should patients with complicated MRSA skin and soft tissue infections be treated?

Answer 25

they should be hospitalized and given IV vanco (or linezolid/dapto if toxin production is an issue)

Question 26

How should complicated polymicrobial infections be treated?

Answer 26

add a MRSA drug to a broad spectrum penicillin (piper/tazo) or imi/cilastatin OR give a 5th generation cephalosporin called CEFTAROLINE (if co-infection with P. aeruginosa or anaerboes is not suspected)

Question 27

Metabolism of Ceftaroline?

Answer 27

IV drug that is predominantly renally eliminated (dose adjustment in RF)

Question 28

AEs of Ceftaroline?

Answer 28

GI disturbance

hypokalemia and phlebitis

C. difficile, ALT/AST elevation, and hemolytic anemia rarely reported

Question 29

How does Dapto work?

Answer 29

IV drug that binds to and depolarizes the abcterial membrane, inhibiting DNA/RNA?protein synthesis

Question 30

AEs of Dapto?

Answer 30

rhabdomyolysis (monitor serum creatine kinase levels)

Question 31

AEs of piperacillin/tazo?

Answer 31

-myelosuppression

Gi disturbance

Question 32

AEs of carbapenems?

Answer 32

seizures at high doses

Question 33

T or F. Dapto, Piperacillin, and carbapenems should be dose-adjusted in RF

Answer 33

T.