Clindamycin

⚠️ Clindamycin carries a well-recognised risk of pseudomembranous colitis due to overgrowth of Clostridioides difficile — this can occur even weeks after therapy has stopped. Use only when clearly indicated and discontinue immediately if significant diarrhoea develops.

📖 About

• Broad-spectrum lincosamide antibiotic active against most Gram-positive cocci (including some MRSA) and anaerobes.
• Particularly valuable in bone, joint, and dental infections when β-lactams are unsuitable.
• Active against penicillinase-resistant staphylococci and many Bacteroides species.
• For official dosing and contraindications always check the BNF link here.

⚗️ Mode of Action

• Binds to the 50S ribosomal subunit, inhibiting bacterial protein synthesis (same site as macrolides and chloramphenicol).
• Primarily bacteriostatic, though can be bactericidal at high concentrations against sensitive organisms.
• Excellent oral bioavailability (~90%) and penetrates well into bone, abscesses, and intracellular spaces.
• Poor cerebrospinal fluid (CSF) penetration → not suitable for meningitis.
• Metabolised hepatically; excreted via bile and urine. Half-life ~2–3 hours (prolonged in hepatic impairment).

🎯 Indications

• Staphylococcal osteomyelitis and septic arthritis.
• Serious streptococcal or pneumococcal infections (e.g. necrotising fasciitis, toxic shock) as adjunct to β-lactam to inhibit toxin production.
• Anaerobic infections (intra-abdominal, pelvic, aspiration pneumonia, dental abscesses).
• Pneumocystis jirovecii pneumonia (with primaquine) and falciparum malaria (with quinine) as alternative regimens.

💊 Adult Dose

• Oral: 150–450 mg every 6 hours; take with a full glass of water to avoid oesophagitis.
• IV: 0.6–2.7 g daily in 2–4 divided doses; may increase to 4.8 g/day in severe infection.
• PCP pneumonia (mild–moderate): 600 mg PO every 8 hours with primaquine.
• Falciparum malaria: 450 mg PO every 8 hours for 7 days (with or following quinine).

⚠️ Cautions

• Monitor LFTs and renal function if therapy exceeds 10 days.
• Risk of C. difficile colitis increases with prolonged or high-dose treatment and in the elderly or hospitalised patients.
• Use cautiously in hepatic impairment — may require dose reduction.

🔄 Interactions

• Antagonistic with macrolides (erythromycin, clarithromycin) — they compete for the same ribosomal site.
• Enhances the effect of neuromuscular-blocking drugs → increased risk of respiratory paralysis during anaesthesia.
• May potentiate warfarin anticoagulant effect via gut flora suppression (monitor INR).

🚫 Contraindications

• Previous pseudomembranous colitis or Clostridioides difficile infection.
• Known hypersensitivity to clindamycin or lincomycin.
• Use in pregnancy only if benefit outweighs risk (crosses placenta but no proven teratogenicity).

💥 Adverse Effects

• Gastrointestinal: Nausea, vomiting, abdominal pain, diarrhoea, oesophagitis.
• Allergic: Rash, urticaria, erythema multiforme, anaphylaxis.
• Haematological: Transient neutropenia, eosinophilia.
• Hepatic: Jaundice, raised transaminases.
• Severe mucocutaneous: Stevens–Johnson syndrome, toxic epidermal necrolysis (rare).
• Pseudomembranous colitis: Due to toxin-producing C. difficile; may develop weeks after discontinuation — stop drug, send stool sample, treat with oral vancomycin or fidaxomicin.

🧠 Pharmacokinetic Notes

• Absorption: Oral bioavailability ≈ 90%; peak plasma within 1 h.
• Distribution: Volume of distribution 0.9 L/kg; good bone, soft tissue, and abscess penetration, but poor CSF entry.
• Protein binding: 60–90% (mainly albumin).
• Metabolism: Hepatic via CYP3A4 to active and inactive metabolites.
• Elimination: Biliary and renal; t½ ≈ 2.5 h (up to 6 h in liver disease).
• Steady-state: Achieved after ~2 days of regular dosing.

💡 Clinical Pearls

• Used with β-lactams for necrotising infections to suppress streptococcal and staphylococcal toxin production.
• In dental abscesses and aspiration pneumonia, clindamycin is preferred over metronidazole when Gram-positive coverage is required.
• Always take capsules with water and remain upright to prevent oesophageal ulceration.
• If diarrhoea develops, stop immediately and investigate for C. difficile — never give antiperistaltic agents.

📚 References

• BNF: Clindamycin
• Sanford Guide to Antimicrobial Therapy, 2024.
• Mandell, Douglas & Bennett’s Principles and Practice of Infectious Diseases, 9th ed.