Reuben Notes
Antibiotics
Drug Names
Penicillins
Cephalosporins
What is the cross-reactivity of cephalosporins and PCN?
1-10% (depending on whom you talk to)
Are cephalosporins contraindicated for a patient with a PCN allergy?
Many people will say yes, and according to Dr. Warren Joseph, "Cephalosporins should be
avoided entirely in patients with a history of anaphylaxis to penicillin." However, he states that
if there is a questionable allergy history (rash or upset stomach), "Cephalosporins can be used
with little worry." Personally, I will give a cephalosporin to a patient with a PCN allergy if all
he or she had was an upset stomach and I document this.
How to treat serious hospital acquired Gram negative infections?
3rd generation cephalosporins, aminoglycoside (i.e. Rocephin, gentamycin)
What is the coverage of cephalosporins for each class?
Name a couple cephalosporins for each generation
How are they excreted?
Renally except for ceftriaxone (renal/hepatic) and cefoperazone (hepatic)
Vancomycin
What is the main indication?
MRSA
What is its spectrum of activity?
All Gram positives, including MRSA and MRSE
What is the dose?
1 g IV q12h with slow infusion
When are levels drawn?
Peak taken 30 min after the 3rd dose
Trough taken 30 min before the 4th dose
What should the peaks and troughs be?
Peak 15-30 mg/mL
Trough <10 mg/mL
How do you adjust the dose?
If the peak is too high, decrease the dose
If the peak is too low, increase the dose
If the trough is too high, increase the interval between doses
If the trough is too low, decrease the interval between doses
What happens when you infuse too quickly?
Red Man syndrome – erythema and pruritis to the head, neck, and upper torso. It is caused by an
anaphylactoid reaction where histamine is released by mast cells. (A different Red Man
syndrome is associated with excessive Rifampin that causes a bright reddish-orange
pigmentation of the skin.)
How can you decrease the risks of Red Man syndrome?
Slow infusion over one hour
How do you treat Red Man syndrome?
Antihistamines (Benadryl 25-50 mg IV q2-4h) until symptoms resolve
Symptoms are self-limiting
What are other side effects?
Ototoxicity and nephrotoxicity
Does the duration a patient has been on vancomycin increase the risks of side effects?
Yes. Vancomycin has a reservoir effect: the more often a patient receives vancomycin, the
higher the chance of getting either ototoxicity or nephrotoxicity. Therefore, use vancomycin
carefully; it is a powerful drug with severe side effects.
When should PO vancomycin be used?
Treatment of Pseudomembranous colitis (125 mg PO q6h)
Bactrim
What is the dose?
One tab PO BID
How much is in the single strength tablet? Double strength?
Single strength – TMP 80 mg / SMX 400 mg
Double strength (DS) – TMP 160 mg / SMX 800 mg
How does it work?
Trimethoprim and sulfamethoxazole inhibit folate synthesis in bacteria which prevents DNA
replication
What is the spectrum of activity?
Broad spectrum covering Gram positives (MRSA) and Gram negatives
Does it cover Pseudomonas?
No
What allergy should be avoided?
Sulfa
What are the side effects?
Hemolytic anemia, hypersensitivity
What are the contraindications?
Patient on oral hypoglycemic or with G6PD deficiencies
Zithromax
Primaxin
Invanz
Zyvox
Quinolones
Aztreonam
Aminoglycosides
What are some major aminoglycosides?
Gentamycin, Tobramycin, Amikacin
What is the spectrum of activity?
Gram negative aerobes
What are the side effects?
Ototoxicity – irreversible
Nephrotoxicity – reversible
Neuromuscular blockade – prevented by slow infusion
What are the doses, peaks, and troughs?
Dose Peak (μg/mL) Trough (μg/mL)
Gent and Tobramycin 3-5 mg/kg q8h 6-10 2
Amikacin 15 mg/kg q8h 20-30 <10
How to dose gentamycin?
CC = (140 - Age) x Weight (in kg)
72 x Serum Creatinine
For females, multiply the CC by 0.85
Clindamycin
Flagyl
MRSA
What antibiotics cover MRSA?
PO – linezolid, Minocycline, Cipro/rifampin, Bactrim/rifampin
IV – vancomycin, linezolid, minocycline, Cipro/rifampin, Bactrim/rifampin, Synercid,
tigecyclin, telavancin
Topical – Bactroban
What are the only FDA-approved drugs for treating MRSA?
vancomycin
linezolid
daptomycin
tigecyclin
telavancin (Vibativ)
VRE
How do you treat VRE?
linezolid or dalfopristin-quinupristin
What is the only PO therapy for VRE?
linezolid
Pseudomonas
What drugs cover Pseudomonas?
Polymicrobial Infections
What are some empiric therapies for polymicrobial foot infections?
Vanco/Zosyn, Clinda/Cipro, Vanco/Invanz
What are the only FDA-approved drugs for treating diabetic foot infections?
(The 3 Z’s)
Zosyn
Zyvox
Invanz
Antibiotic-Associated Diarrhea
What are two main causes of antibiotic-associated diarrhea?
Pseudomembranous colitis – Clostridium difficile
Non-specific colitis – Staph aureus
How to you test for Clostridium difficile?
Order ―check stool for C diff‖
What is the most common cause of Clostridium difficile colitis?
clindamycin (though any antibiotic can cause it)
How do you treat Clostridium difficile colitis?
Vanco 125 mg PO q6h
Flagyl 500 mg PO TID
Miscellaneous
What antibiotics are metabolized by the liver?
Can antibiotics affect PT/INR?
Yes. Antibiotics can affect normal flora, which alters Vitamin K. Therefore, the PT/INR can
increase
What can β-lactams cause?
Leukopenia
What is the MOA of aminoglycosides? Macrolides?
Aminoglycosides bind to bacterial 30s ribosomes inhibiting protein synthesis
Macrolides bind to bacterial 50s ribosomes inhibiting protein synthesis
(A boy at 30 does not become a Man until 50)
What antibiotics can be safely used with PMMA beads?
Vancomycin, gentamycin, tobramycin, cefazolin
The curing of PMMA is exothermic, therefore the antibiotic must be not be heat-labile
What open fractures should be treated with antibiotics?
Grades 2 and 3
Bugs and Drugs
Gram Positives
What are Gram positive, catalase positive cocci in clusters?
Staphylococcus aureus
DOC for Staph?
Keflex or Ancef
Alternative for Staph?
clindamycin, Levaquin, Vancomycin, Azithromycin, dicloxacillin, nafcillin
Alternative for Staph if PCN allergy?
clindamycin, Levaquin, Vancomycin, Azithromycin
What if the organism is resistant to methicillin?
MRSA (methacillin-resistant Staph aureus)
DOC for MRSA?
Vanco IV, Bactrim PO (if sensitive)
Alternative for MRSA?
Synercid or linezolid
Topical DOC for MRSA?
Bactroban
DOC for Strep?
Keflex or Ancef
What are Gram positive, catalase negative cocci that are in pairs or chains?
Streptococcus
DOC for Strep?
Keflex or Ancef
Alternative for Strep?
clindamycin, Levaquin, vancomycin
Alternative for Strep in PCN allergy?
clindamycin, Levaquin, vancomycin
DOC for Enterococcus?
amoxicillin or vancomycin
Alternative for Enterococcus?
Augmentin, linezolid
What if the organism is resistant to vancomycin?
VRE (vancomycin-resistant Enterococcus)
DOC for VRE?
linezolid or Synercid
DOC for Diptheroids?
vancomycin
Gram Negatives
What is a short, Gram negative rod?
Escherichia coli
DOC for E. coli?
Keflex or Ancef
Alternative for E. coli if PCN allergy?
Cipro or Levaquin
DOC for Proteus?
Keflex or ampicillin
Alternatives for Proteus if PCN allergy?
Cipro or Levaquin
DOC for E/C/S/M group?
Quinolone (Cipro or Levaquin)
Alternatives for E/C/S/M group?
3rd generation cephalosporin, Aztreonam, Bactrim
What is a small Gram negative rod with pili and polar flagella?
Pseudomonas aeruginosa
DOC for Pseudomonas?
Cipro
Alternative for Pseudomonas?
3rd gen cephalosporins, Aztreonam, Zosyn, Timentin
How does Pseudomonas typically present?
blue-green purulence with grape-like odor
What Gram negative spirochete causes Lyme disease?
Borrelia burgdorferi
DOC for Lyme disease?
doxycyline or Rocephin
Alternative for Lyme disease?
amoxicillin
Anaerobes
DOC for Bacteroides?
Augmentin, Zosyn, Unasyn, Timentin
Alternatives for Bacteroides if PCN allergy?
clindamycin/Cipro, Primaxin, Flagyl
What is a large, Gram positive, anaerobic, "racquet-shaped" rod that forms spores?
Clostridium perfringens
DOC for Clostridium?
Penicillin, imipenem, clindamycin, tetracycline
What are two soft tissue clinical manifestations caused by Clostridium?
Anaerobic cellulitis and gas gangrene
Why is gas gangrene a surgical emergency?
It rapidly progresses to shock and renal failure and is fatal in 30% of cases
Less Common Organisims
DOC for Aeromonas?
Cipro PO/IV
Alternative for Aeromonas?
Bactrim
DOC for Pseudomonas cepacia?
Bactrim
Alternative for Pseudomonas cepacia?
Ceftazidime
DOC for Necrotizing Fasciitis?
Primaxin
DOC for superficial thrombophlebitis?
Timentin
DOC for Gonorrhea?
Ceftriaxone or PCN if sensitive
DOC of Cutaneous Larva Migrans?
Promethia under occlusion
Miscellaneous
What organisms may form gas in soft tissue?
Gram positive – Clostridium perfringens, Staphylococcus, Streptococcus, Peptostreptococcus
Gram negative – Bacteroides, E. coli, Klebsiella, Serratia
What are some anaerobes?
Gram positive – Actinomyces, Clostridium, Peptostreptococcus
Gram negative – Bacteroides, Fusobacterium
What is the drug of choice (DOC) for a patient with diabetes and a PCN allergy?
clindamycin
DOC for severe limb-threatening infection?
Primaxin
What are most common organisms of bite wounds?
Human – Eikenella corrodens
Cat and dog – Pasteurella multocida
What is Gram negative rod is associated with dog bites?
DF-2
DOC for cat and dog bites?
Augmentin
What are the most common organisms causing cellulitis?
Staph and Strep
Which type of Strep can cause impetigo, cellulitis, and erysipelas?
Group A Strep
What is the difference between cellulitis and erysipelas?
Cellulitis – confined superficial infection
Erysipelas – superficial infection that extends into the lymphatics
What is the most common organism that causes acute hematogenous osteomyelitis?
Staphylococcus aureus (adults), Gram negative rods (elderly)
What is the most common organism that causes osteomyelitis following a puncture wound?
Pseudomonas aeruginosa
What is an anaerobic Gram positive filamentous bacteria?
Actinomyces
What organism may be found following a puncture wound in the ocean?
Vibrio vulnificus
What type of bacteria is gonorrhea?
Gram negative diplococci
What is gonorrhea cultured on?
Chocolate agar
What is the treatment for gonorrhea?
Ceftriaxone
If a patient is currently on an antibiotic, how long should it be stopped before taking a wound culture?
At least 48 hours (if possible)