Penicillins 9 drugs Break the bacterial cell wall — the original antibiotics, still frontline for many infections.
Treats: Strep throat · Skin infections · Pneumonia · Syphilis
Anaphylaxis in true penicillin allergy; cross-reactivity concern with cephalosporins; diarrhea/C. diff. amoxicillin, amoxicillin-clavulanate, penicillin G, penicillin VK, ampicillin…
Cephalosporins 9 drugs Cell-wall antibiotics organized by generations — broader gram-negative reach as the number climbs.
Treats: Pneumonia · UTIs · Skin infections · Meningitis (ceftriaxone)
Cross-reactivity with penicillin allergy; ceftriaxone precipitates with calcium in neonates; disulfiram-like reaction (cefotetan) with alcohol. cephalexin, cefazolin, cefuroxime, cefdinir, ceftriaxone…
Macrolides 3 drugs Block bacterial protein-making — key for atypical pneumonia and penicillin-allergic patients.
Treats: Community-acquired pneumonia · Pertussis · Chlamydia · H. pylori
QT prolongation and torsades; major CYP3A4 inhibitors (erythromycin, clarithromycin) — many interactions; GI upset. azithromycin, clarithromycin, erythromycin
Fluoroquinolones 4 drugs Broad-spectrum antibiotics that block bacterial DNA copying — powerful but carry serious warnings.
Treats: Complicated UTI/pyelonephritis · Pneumonia · Intra-abdominal infection · Bone/joint infection
Boxed warnings: tendon rupture, peripheral neuropathy, CNS effects, aortic aneurysm risk, and worsening myasthenia gravis; QT prolongation; reserve for when alternatives fail. ciprofloxacin, levofloxacin, moxifloxacin, ofloxacin
Tetracyclines 4 drugs Protein-synthesis blockers used for acne, tick-borne disease, and atypical infections.
Treats: Acne · Rocky Mountain spotted fever · Lyme disease · Atypical pneumonia
Tooth staining and bone effects — avoid in pregnancy and children under 8; photosensitivity; binds to calcium/iron/antacids (separate dosing). doxycycline, minocycline, tetracycline, tigecycline
Aminoglycosides 3 drugs Potent gram-negative killers reserved for serious infections — narrow safety margin.
Treats: Serious gram-negative infections · Sepsis (synergy) · Endocarditis
Nephrotoxicity and irreversible ototoxicity — trough level and renal monitoring; worse with other nephrotoxins and loop diuretics. gentamicin, tobramycin, amikacin
Sulfonamides & Other Antibiotics 11 drugs A grab-bag of high-yield agents — Bactrim, nitrofurantoin, metronidazole, clindamycin, and the anti-MRSA drugs.
Treats: UTIs · MRSA (Bactrim, vancomycin, linezolid) · C. difficile · Anaerobic infections
Bactrim: Stevens-Johnson, hyperkalemia, raises INR; metronidazole + alcohol reaction; clindamycin is the classic C. diff culprit; vancomycin infusion reaction and nephrotoxicity; linezolid causes serotonin syndrome (MAO inhibitor). trimethoprim-sulfamethoxazole, nitrofurantoin, metronidazole, clindamycin, vancomycin…
Antifungals 9 drugs Kill or stall fungi — from topical yeast creams to life-saving IV amphotericin.
Treats: Candidiasis · Tinea/ringworm · Onychomycosis · Invasive aspergillosis
Azoles are strong CYP inhibitors (huge interaction list) and hepatotoxic; amphotericin B — 'ampho-terrible' — nephrotoxicity and infusion reactions. fluconazole, itraconazole, voriconazole, posaconazole, nystatin…
Antivirals (Non-HIV/HCV) 7 drugs Blunt viral replication for herpes, flu, COVID, and CMV.
Treats: Herpes/shingles · Influenza · COVID-19 · CMV
Acyclovir crystal nephropathy — hydrate; nirmatrelvir-ritonavir (Paxlovid) has major CYP drug interactions; ganciclovir causes bone-marrow suppression. acyclovir, valacyclovir, oseltamivir, nirmatrelvir-ritonavir, ganciclovir…
Antiretrovirals (HIV) 6 drugs Combination therapy that suppresses HIV to undetectable levels — usually a single-tablet regimen now.
Treats: HIV treatment · HIV pre-exposure prophylaxis (PrEP) · Post-exposure prophylaxis
Never use as monotherapy — resistance; abacavir hypersensitivity (HLA-B5701 testing); many CYP interactions with boosters; adherence is everything. bictegravir-emtricitabine-tenofovir, dolutegravir, emtricitabine-tenofovir, efavirenz, raltegravir…
Antitubercular Agents 5 drugs The multi-drug, months-long regimen that cures TB — remembered as RIPE.
Treats: Active tuberculosis · Latent TB
Isoniazid and pyrazinamide are hepatotoxic (give B6 with INH to prevent neuropathy); rifampin turns secretions orange and is a potent CYP inducer; ethambutol causes optic neuritis. isoniazid, rifampin, pyrazinamide, ethambutol, rifabutin
