Clindamycin Flashcards
What is the mechanism of action of clindamycin?
Clindamycin binds reversibly to the 50S ribosomal subunit (at the peptidyl transferase center), inhibiting peptide bond formation and translocation. This prevents protein synthesis (generally bacteriostatic).
Describe the spectrum of activity of clindamycin.
Clindamycin covers many anaerobes (especially anaerobes ‘above the diaphragm’ like Bacteroides fragilis, Clostridium perfringens) and Gram-positive cocci (Strep pyogenes, MSSA, and even some CA-MRSA). It does not cover Gram-negative aerobes.
How can bacteria develop resistance to clindamycin?
The main mechanism is modification of the ribosomal binding site via methylation of the 23S rRNA (erm gene), which confers cross-resistance to macrolides and streptogramin B (MLS_B resistance). Mutations in the ribosomal RNA or enzymatic inactivation can also confer resistance. Inducible resistance can be tested by the D-test in erythromycin-resistant, clindamycin-susceptible Staph.
Outline key pharmacokinetic features of clindamycin.
Clindamycin is well absorbed orally and also given IV. It penetrates well into most tissues including bone, but has poor CSF penetration. It is extensively metabolized in the liver and mainly excreted in bile (minor renal excretion). It has a moderate half-life (~2-3 hours) and is usually dosed 3-4 times daily. No major adjustment is needed for mild renal impairment, but caution in severe hepatic dysfunction.
What major drug interactions involve clindamycin?
Clindamycin is not a significant CYP inhibitor or inducer. However, it may potentiate neuromuscular blockers (additive skeletal muscle relaxant effect). Avoid using concurrently with chloramphenicol or macrolides as they have overlapping binding sites (antagonistic effects). Also, any antibiotic that reduces gut flora (like clindamycin) can enhance warfarin effect by reducing vitamin K-producing bacteria.
What are common clinical uses for clindamycin?
Clindamycin is used for anaerobic infections (e.g., aspiration pneumonia, lung abscesses, oral infections) and Gram-positive infections in patients with penicillin allergy. It’s first-line for anaerobic infections above the diaphragm. Also used for severe Group A strep (to reduce toxin production in toxic shock or necrotizing fasciitis, alongside beta-lactams). Topically, clindamycin is used for acne vulgaris. It’s an alternative for bacterial vaginosis and some protozoal infections like Babesia (with quinine) or malaria (with quinine in pregnancy).
In which patients is clindamycin use contraindicated or should be cautious?
Avoid in patients with a history of antibiotic-associated colitis (pseudomembranous colitis) or those who have had C. difficile infection, since clindamycin is high-risk for C. diff. Use with caution in patients with severe hepatic impairment (due to liver metabolism) and adjust dosing interval if needed. Obviously contraindicated in those with a known clindamycin allergy.
List major adverse effects of clindamycin.
The most notorious adverse effect is Clostridioides difficile colitis (pseudomembranous colitis) due to elimination of gut flora. Other effects: diarrhea (even without C. diff), nausea, rash. Rarely, can cause hepatotoxicity or agranulocytosis. Also can cause pain and irritation at injection site with IV use.
What is a high-yield mnemonic related to clindamycin?
“Clindamycin = anaerobes ABOVE the diaphragm; Metronidazole = anaerobes BELOW.” This helps recall clindamycin’s use for oral/lung anaerobic infections. Also remember “Clin-di” sounds like “clean the DIE (gut)”, hinting at C. diff risk.
