STEPTRACKERPHARMACOLOGY + MICROBIOLOGY | ANTIMICROBIALS | HIGH-YIELD REVIEW
Protein Synthesis Inhibitors
Bacterial ribosomes (70S) differ from ours (80S), so drugs can block the 30S or 50S subunit selectively — the subunit, spectrum and signature toxicity identify each class.
FOCUS ON
30S:
aminoglycosides (gentamicin, tobramycin, amikacin, streptomycin, neomycin) — bind 30S → misreading, block initiation;
bactericidal, concentration-dependent; need
O₂ for uptake (no anaerobes); synergy with β-lactams; toxicity —
nephrotoxicity (ATN),
ototoxicity (↑ with loops),
NM blockade, teratogen.
Tetracyclines (doxycycline, minocycline, tigecycline) — block aminoacyl-tRNA binding; rickettsia, chlamydia, Lyme, mycoplasma, acne, MRSA skin; avoid with
Ca²⁺/Mg²⁺/Fe²⁺, children < 8 (teeth), pregnancy;
photosensitivity, pill esophagitis.
50S:
macrolides (azithromycin, clarithromycin, erythromycin) — block translocation; atypicals, pertussis, chlamydia, MAC;
QT, GI motility, cholestasis, CYP3A4 inhibition (not azithromycin), infantile pyloric stenosis.
Clindamycin — anaerobes above diaphragm, GAS toxin suppression, MRSA;
C. difficile.
Linezolid — blocks initiation complex; MRSA, VRE;
thrombocytopenia, optic/peripheral neuropathy,
serotonin syndrome (MAO inhibition).
Chloramphenicol — peptidyltransferase;
aplastic anemia, gray baby.
Streptogramins (quinupristin-dalfopristin).