Clindamycin
Clindamycin
Generic Name
Clindamycin
Mechanism
Clindamycin is a lincosamide antibiotic that inhibits bacterial protein synthesis by binding to the 50S subunit of the bacterial ribosome. This action blocks peptidyl transferase, preventing the translocation of the peptidyl‑tRNA and thereby stopping elongation of the nascent polypeptide chain. It is bacteriostatic against many Gram‑positive cocci and anaerobes, and bactericidal against Clostridioides difficile and many anaerobes in high concentrations.
Pharmacokinetics
| Parameter | Typical Value | Notes |
| Absorption | Oral: 70‑80 % bioavailability | Rapid absorption; maximal plasma concentration 1–2 h. |
| Distribution | Volume of distribution: ~1.5 L/kg | Good penetration into tissues (skin, bone, GI tract, bone marrow, CSF via meninges). |
| Metabolism | Hepatic *CYP3A4* → glucuronide conjugates, entero‑hepatic recirculation | Variable due to gut flora metabolism. |
| Excretion | ~60 % renal (urine & feces); ~40 % biliary | Renal dosing adjustment in CrCl < 30 mL/min. |
| Half‑life | 2–3 h (oral), ~8 h (IV) | Enables 12‑hr dosing for oral therapy. |
Indications
- Skin & soft‑tissue infections (cellulitis, abscesses, necrotizing fasciitis)
- Bone & joint infections (osteomyelitis, septic arthritis)
- Dental infections & postoperative prophylaxis
- Intra‑abdominal sepsis (including peritonitis)
- Bacterial vaginosis (once daily oral)
- Clostridioides difficile colitis (oral or IV in severe cases)
- Empiric therapy for intra‑abdominal, pelvic, or gynecologic infections when anaerobes are likely.
Contraindications
- Hypersensitivity to clindamycin, lincomycin, or other lincosamides.
- History of severe enterocolitis (C. difficile) – use with extreme caution.
- Sickle‑cell disease: increases risk of non‑infectious lung injury.
- Pregnancy: category C – limited data; use only if benefits outweigh risks.
- Liver dysfunction: reduced metabolism; can lead to higher plasma levels.
- Drug interactions: potentiates opioid analgesia, antidiarrheals, and may increase hepatotoxicity with azoles.
Dosing
| Form | Adult Dosing (e.g., 60 kg) | Pediatric (weight‑based) | Comments |
| Oral | 600 mg q12 h (4 × 600 mg/day) | 20 mg/kg q12 h (max 600 mg) | Start with 2 × 25 mg tablets; may take 2–3 days for full effect. |
| IV | 600 mg q12 h (18 mg/kg) | 15–20 mg/kg q12 h | Use 10 % aqueous solution; infusion over 30 min (IV or IM). |
| IV for severe C. difficile | 600 mg q8 h (12 mg/kg) | 10 mg/kg q8 h | Can shorten course in severe disease. |
• For most infections, 12‑hour dosing is sufficient; for severe intra‑abdominal sepsis, a 6‑hour q6 h schedule may be warranted.
• Loading dose: IV 600 mg q12 h for 2 days in high‑risk infections.
• Transition: May switch from IV to oral once patient can tolerate PO; continue 2–3 days of IV before conversion.
Adverse Effects
- Common
- Gastrointestinal: diarrhea, nausea, vomiting, abdominal cramping
- Skin: rash, pruritus
- Oral irritation: candidiasis, stomatitis
- Serious
- Clostridioides difficile‑associated colitis (pseudomembranous) – red‑tinged stool, fever, severe abdominal pain
- Severe cutaneous adverse reactions (SJS/TEN) – treat immediately, discontinue drug.
- Non‑infectious lung injury in sickle‑cell or chronic hemolytic disorders
- Hepatotoxicity: transaminitis, jaundice (rare)
Monitoring
- Baseline labs: CBC, CMP (especially hepatic panel) before long‑term therapy.
- During therapy: monitor for signs of pseudomembranous colitis (frequency, stool appearance).
- Drug interactions: watch for increased serum levels of azoles, opioids, and antacids that alter absorption.
- Renal function: If CrCl < 30 mL/min, reduce IV dosing (600 mg q12 h → 300 mg q12 h).
Clinical Pearls
- Geographic penetration: Clindamycin reaches high concentrations in bone, abscesses, and the GI lumen – ideal when anaerobes dominate.
- C. difficile: Because it suppresses anaerobic flora less than broad‑spectrum beta‑lactams, it is preferred for initial therapy but avoid it if recurrent disease.
- Colonic bioavailability: The drug’s large molecular weight limits absorption in the colon; this is advantageous for treating colonic infections but reduces systemic exposure.
- Synergy: Use clindamycin with beta‑lactams (e.g., ampicillin) in mixed flora infections for enhanced coverage of Gram‑positives and anaerobes.
- Enteric coating: Oral preparations are coated to avoid gastric upset, which also reduces early transit to the colon (less dysbiosis).
- Sick‑cell caution: In patients with sickle‑cell disease, clindamycin can precipitate acute chest syndrome; a lower dose or alternative agent is prudent.
- Pediatric dosing: Weight‑based dosing to avoid supra‑therapeutic levels, particularly in infants with immature hepatic metabolism.
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• Key takeaways:
• Clindamycin is a versatile lincosamide with strong anaerobic coverage and excellent tissue penetration.
• Use with caution in C. difficile predisposition and sickle‑cell patients.
• Maintain dosing adjustments for renal impairment; monitor for GI and hepatic toxicity.
These concise, keyword‑rich details should assist medical students and clinicians in quickly referencing clindamycin’s essential pharmacology.