Antibiotics — pick the right one

Class-by-class with coverage, side effects, and the test-worthy gotchas.

Select any text to highlight it or make a flashcard.

◆Penicillins / β-lactams

•Penicillin G/V: strep, Treponema, Listeria, susceptible enterococcus
•Amoxicillin / amox-clav: otitis media, sinusitis, dental, +H. influenzae, +anaerobes (clav)
•Antipseudomonal pens (piperacillin-tazobactam): broad gram-neg + anaerobes + Pseudomonas
•Cephalosporins: 1st gen (cefazolin) skin/preop; 3rd gen (ceftriaxone) CAP/meningitis; 4th gen (cefepime) Pseudomonas; 5th gen (ceftaroline) MRSA
•Carbapenems (meropenem, imipenem): broadest gram-neg/anaerobic; reserve for resistant; seizure risk (imipenem)
•Side effects: rash, anaphylaxis, C. diff; cefepime → neurotoxicity in renal failure

•Atypical pneumonia (Mycoplasma, Legionella, Chlamydia), pertussis, H. pylori (clarithro)
•Side effects: QT prolongation, GI motility (erythro = pro-kinetic), hearing loss with high dose

•Cipro: UTI, GI, Pseudomonas; weak gram-positive
•Levo, moxi: 'respiratory FQ' for CAP
•BOXED warnings: tendon rupture (esp Achilles + steroids), QT prolongation, aortic aneurysm/dissection, peripheral neuropathy, C. diff
•Avoid in pregnancy and children (cartilage); avoid with steroids in elderly

•Gram-negative; synergy with β-lactam for endocarditis (enterococcus)
•Side effects: NEPHROTOXICITY, OTOTOXICITY (irreversible), neuromuscular blockade
•Once-daily dosing safer; monitor peaks/troughs; avoid with loops

•MRSA, severe gram-positive infections
•Side effects: red man syndrome (rate-related infusion reaction; pre-treat with antihistamine, slow infusion), nephrotoxicity, ototoxicity
•PO vancomycin: C. diff (NOT absorbed)

•TMP-SMX (Bactrim): UTI, MRSA skin, PCP, toxoplasmosis prophylaxis; hyperK, photosensitivity, Stevens-Johnson, kernicterus in neonates
•Tetracyclines (doxy): atypicals, Lyme, rickettsia, acne; PHOTOSENSITIVITY, tooth discoloration in kids/preg, esophagitis
•Metronidazole: anaerobes, C. diff, BV, trichomonas, H. pylori; disulfiram-like with alcohol, peripheral neuropathy
•Clindamycin: anaerobes, MRSA; C. DIFF (classic), pseudomembranous colitis
•Linezolid: MRSA, VRE; serotonin syndrome, lactic acidosis, bone marrow suppression
•Daptomycin: MRSA, VRE; CANNOT use in pneumonia (inactivated by surfactant); rhabdo, eosinophilic pneumonia

Drug	Test-worthy warning
FQ (cipro/levo)	Tendon rupture, QT, aorta, neuropathy
Aminoglycosides	Nephro + irreversible ototoxicity
TMP-SMX	HyperK, SJS, kernicterus in newborns
Tetracyclines	Photosensitivity; not in kids/pregnancy
Metronidazole	Disulfiram with alcohol
Clindamycin	C. difficile colitis
Daptomycin	Doesn't work for pneumonia
Linezolid	Serotonin syndrome with SSRIs

◆Empiric meningitis in adults: vancomycin + ceftriaxone (+ ampicillin if >50 or immunocompromised for Listeria)
◆Empiric CAP (outpatient): amoxicillin or doxycycline (or azithro if no comorbidities); inpatient ICU: β-lactam + macrolide OR β-lactam + FQ
◆C. diff treatment: ORAL vancomycin OR oral fidaxomicin (first-line, replacing metronidazole)
◆MRSA skin/soft tissue: TMP-SMX, doxycycline, clindamycin; serious infections: vancomycin or linezolid
◆Pseudomonas: pip-tazo, cefepime, ceftazidime, meropenem, FQs (cipro best), aminoglycosides

Quick check

Test yourself before moving on. ~1 min.

Done reading?

Track your progress by marking this complete.