Antibiotics

Question 1

Classes of antibiotics

Answer 1

• Carbapenems
• Aminoglycosides
• Penicillins
• Cephalosporins
• Fluoroquinolones
• Macrolides
• Tetracyclines
• Anti-anaerobics
• Others
• “Big Guns”

Question 2

Carbapenems

Answer 2

• Imipenem/cilastatin (Primaxin or “gorillamycin”)
• Meropenem
• Ertapenem (Invanz)

These are beta lactam antibiotics, meaning they have a beta lactam ring in their molecular structure

All beta lactam antibiotics bind to penicillin binding proteins (PBPs) in the bacteria’s cell wall and inhibit them

PBPs are a group of proteins in some bacteria that have a affinity for binding to penicillin and are essential for cell wall synthesis

Question 3

Impipenem/cilastatin

Answer 3

Carbapenem

• 500 mg q8h IV
• Trade name = Primaxin
• Nickname = Gorillamycin
• Imipenem = broad spectrum beta lactam antibiotic
• Cilastatin = inhibits renal clearance of imipenem
• First line antibiotic for necrotizing fasciitis
• Renal clearance
• Cross reactivity with PCN allergy (NOT pen safe)
• Hard to send patient home on this antibiotic due to frequency in dosing

Question 4

Meropenem

Answer 4

Carbapenem

• 500 mg to 1 g q8h IV
• No trade name
• Carbapenem antibiotic (PBP inhibitor)
• NOTE: PBP = penicillin binding protein, a group of proteins in some bacteria that have a affinity for binding to penicillin and are essential for cell wall synthesis, all beta lactam antibiotics bind to PBPs and inhibit them, killing the bacteria
• Meropenem covers some strep (not strep D), no staph coverage
• Covers pseudomonas and bacteroides (BETTER gram negavtive coverage than imipenem)

Question 5

Ertapenem

Answer 5

Carbapenem

• 1 g q24h IV
• Trade name = Invanz
• Covers all staph (except MRSA), all strep (except strep D)
• No pseudomonal coverage
• Covers ALL anaerobes
• Recommended for LE infections
• Once daily dosing which is convenient

Question 6

Aminoglycosides

Answer 6

• Streptomycin
• Gentamycin
• Kanamycin
• Amikacin
• Tobramycin
• Neomycin

Question 7

Which aminoglycoside can be used in antibiotic beads?

Answer 7

Gentamycin

Question 8

General aminoglycoside information

Answer 8

• Protein synthesis inhibitors (bind to 30s subunit)
• Used to treat serious gram negative aerobic bacteria
• Used with a beta-lactam antibiotic to treat serious gram negative infections
• IRREVERSIBLE nephrotoxicity and ototoxicity
• Need to check renal function and order peaks and troughs to monitor
• Usually there is a safer alternative
• Rare to prescribe these

Question 9

Penicillins

Answer 9

• 1st generation: naturally occurring
• 2nd generation: penicillinase producing (naf, diclox/clox, ox, meth)
• 3rd generation: (amoxicillin, ampicillin - tx some gram neg)
• 4th generation: big gun antibiotics, cover pseudomonal and enterococcus

Question 10

Nafcillin

Answer 10

2nd generation

• Dose: 1 g q4 hours IV
• DRUG OF CHOICE for MSSA
• Biliarily cleared

Question 11

Dicloxacillin/cloxacillin

Answer 11

2nd generation

• Dose: 500 mg QID PO
• DRUG OF CHOICE for MSSA
• Coverage: mild to moderate staph infections, staph skin cellulitis or skin infection (folliculitis, boils, carbuncles, etc.)
• Used for osteo, septic arthritis, septicemia, empiric endocarditis
• Renal clearance

Question 12

Amoxicillin/clavulanic acid

Answer 12

3rd generation

• Augmentin
• Dose: 875 mg PO BID (125 mg clavulanic acid in all doses)
• EMPIRIC antibiotic for diabetic wounds
• Drug of choice for human/animal bite wounds
• Covers most common gram negative anaerobe isolated in diabetic wounds - BACTEROIDES FRAGILIS

Question 13

Ampicillin/sulbactam

Answer 13

3rd generation

• Unasyn
• Dose: 3 g q6 hours IV
• Not absorbed well oral, so used IV
• Covers
• DRUG OF CHOICE for GAS GANGRENE