PK PD
Which antibiotics exhibit time-dependent killing?
Beta-lactams (penicillins, cephalosporins, carbapenems) and vancomycin — efficacy correlates with the % of the dosing interval that drug concentration stays above the MIC
What are adverse effects of fluoroquinolones?
QT prolongation, tendon rupture/tendinitis, peripheral neuropathy, CNS effects (seizures, confusion), photosensitivity, and hypo/hyperglycemia.
Which antibiotics will treat C. diff?
Oral vancomycin and fidaxomicin are first-line; metronidazole is an alternative/adjunct for some cases.
First-line antibiotics to treat community-acquired pneumonia on the medical floor?
A respiratory fluoroquinolone (levofloxacin) alone, OR a beta-lactam (e.g., ceftriaxone) plus a macrolide (e.g., azithromycin)
Which penicillin can you use to treat Pseudomonas?
Piperacillin (typically given as piperacillin-tazobactam)
How can you increase the killing of a time-dependent antibiotic?
Increase the time the drug concentration stays above the MIC — e.g., give more frequent dosing, or use extended/continuous infusions rather than raising the dose itself.
When is a vancomycin trough goal of 15–20 mg/L used?
For more severe infections — bacteremia, endocarditis, osteomyelitis, meningitis, or hospital-acquired/MRSA pneumonia.
Which antibiotics cover MRSA?
Vancomycin, linezolid, daptomycin, ceftaroline, TMP-SMX
First-line antibiotics to treat community-acquired pneumonia in the ICU?
A beta-lactam (ceftriaxone, ampicillin-sulbactam) plus either a macrolide or a respiratory fluoroquinolone; add MRSA/Pseudomonas coverage if risk factors are present
What cephalosporin does not need renal adjustment?
Ceftriaxone — it's primarily eliminated via biliary/fecal excretion.
What is MIC?
Minimum Inhibitory Concentration — the lowest antibiotic concentration that prevents visible growth of an organism in vitro.
When is a vancomycin trough goal of 10–15 mg/L used?
For less severe or uncomplicated infections, such as skin/soft tissue infections.
What class of antibiotics reliably covers ESBL-producing organisms?
Carbapenems (meropenem, imipenem, ertapenem, doripenem) are the treatment of choice for serious ESBL infections.
What is empiric treatment for hospital-acquired pneumonia with risk factors for MRSA and Pseudomonas?
Vancomycin or linezolid (MRSA coverage) PLUS an anti-pseudomonal beta-lactam (cefepime, pip-tazo, or meropenem)
What are the first generation cephalosporins?
Cefazolin (IV) and cephalexin (oral)
Are aminoglycosides time-dependent or concentration-dependent killers?
Concentration-dependent killers
What is the goal AUC for vancomycin?
AUC24/MIC ratio of 400–600
What is the drug of choice for Enterococcus faecalis endocarditis (susceptible strain)?
Ampicillin, typically combined with either gentamicin or ceftriaxone for synergy
Why do we monitor QT interval closely when using fluoroquinolones or macrolides, especially together or with other QT-prolonging drugs?
Both classes can independently prolong the QT interval, raising the risk of torsades de pointes; combining QT-prolonging agents is additive risk and generally avoided
Which cephalosporins can treat Pseudomonas?
Ceftazidime (3rd gen) and cefepime (4th gen).
What are the adverse effects of aminoglycosides?
Nephrotoxicity and ototoxicity; also neuromuscular blockade at high doses.
Does ciprofloxacin cover Strep pneumoniae?
No — ciprofloxacin has poor/unreliable activity against Strep pneumoniae. Respiratory fluoroquinolones (levofloxacin, moxifloxacin) are needed for reliable pneumococcal coverage.
What is empiric antibiotic coverage for febrile neutropenia?
An anti-pseudomonal beta-lactam — cefepime, piperacillin-tazobactam, or meropenem — as monotherapy.
A patient with a non-severe penicillin allergy needs treatment for MSSA bacteremia — what would you use?
Cefazolin (or nafcillin/oxacillin) is preferred over vancomycin for MSSA, vancomycin is reserved for patients with a true severe/anaphylactic beta-lactam allergy.
Does ertapenem cover Pseudomonas?
No — ertapenem lacks activity against Pseudomonas aeruginosa and Acinetobacter, unlike meropenem, imipenem, and doripenem.