Clindamycin

Clindamycin is a lincosamide with good activity against Gram-positive cocci and anaerobes and excellent bone and soft tissue penetration. It also suppresses toxin production by Staphylococcus aureus and group A streptococci. Clostridioides difficile infection is its main hazard.

Classification. Lincosamide.

Mechanism. Binds the 50S ribosomal subunit and blocks protein synthesis; bacteriostatic, sometimes bactericidal; reduces toxin synthesis.

Spectrum. Staphylococcus aureus (many MRSA in the community), streptococci, anaerobes including Bacteroides (resistance rising) and Clostridium perfringens, Plasmodium and Babesia (adjunct), Toxoplasma (adjunct), Pneumocystis (with primaquine). Not active against enterococci, Gram-negative aerobes or MRSA that carry inducible resistance (positive D-test).

Pharmacokinetics. Oral bioavailability about 90%. Half-life 2 to 3 hours. Protein binding 90%. Good penetration into bone, abscesses and macrophages; poor CSF penetration. Hepatic metabolism.

Maximum 1.8 g daily orally and 4.8 g daily IV.

Adults

• Oral: 150 to 450 mg every 6 hours (300 to 450 mg every 6 hours in most infections).
• IV or IM: 600 to 900 mg every 8 hours (up to 900 mg every 6 to 8 hours in severe infection). IM single injection not over 600 mg.
• Skin and soft tissue infection (including MRSA): 300 to 450 mg orally every 6 to 8 hours for 5 to 10 days.
• Toxin suppression in necrotising infection or toxic shock: 900 mg IV every 8 hours with a beta-lactam, until stable.
• Bone and joint infection: 600 mg IV every 8 hours then 300 to 450 mg orally every 6 hours; total 6 weeks or longer by site.
• Dental and anaerobic infection: 300 mg orally every 6 hours for 5 to 7 days.
• Pelvic inflammatory disease: 900 mg IV every 8 hours with gentamicin, then oral 450 mg every 6 hours to complete 14 days.
• Pneumocystis pneumonia (alternative): clindamycin 600 to 900 mg IV every 6 to 8 hours (or 300 to 450 mg orally every 6 to 8 hours) with primaquine 30 mg base daily for 21 days.
• Toxoplasmosis (alternative): 600 mg every 6 hours for at least 6 weeks with pyrimethamine and folinic acid.
• Severe malaria, quinine partner: clindamycin 10 mg/kg every 12 hours for 7 days.
• Endocarditis prophylaxis in penicillin allergy: 600 mg orally as a single dose 30 to 60 minutes before the procedure.

Children. Oral 10 to 25 mg/kg/day divided every 6 to 8 hours (up to 40 mg/kg/day in severe infection). IV or IM 20 to 40 mg/kg/day divided every 6 to 8 hours (maximum 2.7 g daily). Neonates 15 to 20 mg/kg/day divided every 6 to 8 hours, with lower doses in preterm infants.

Alternatives. Trimethoprim sulfamethoxazole, doxycycline, linezolid, amoxicillin clavulanate, metronidazole.

Boxed-warning level risk. Clostridioides difficile infection, which can be fatal and can start weeks after treatment; use only where benefit clearly outweighs risk.

Contraindications. Lincosamide hypersensitivity; history of Clostridioides difficile colitis (relative).

Adverse effects. Diarrhoea, nausea, abdominal pain, rash, metallic taste, thrombophlebitis with IV use. Serious: Clostridioides difficile colitis, severe skin reactions including DRESS, hepatotoxicity, neutropenia, anaphylaxis.

Interactions. Neuromuscular blockers (prolonged block); erythromycin and other macrolides (antagonism: do not combine); rifampicin (lower clindamycin levels); strong CYP3A4 inducers and inhibitors; warfarin (INR rise).

Common prescribing errors. Bolus IV injection, using it for sore throat or minor infection, inducible resistance missed in staphylococcal infection, and continuing it despite new diarrhoea.

Special groups

• Pregnancy: acceptable when needed. Breastfeeding: acceptable; watch the infant for diarrhoea.
• Older adults: higher risk of Clostridioides difficile infection.
• Kidney impairment: no adjustment.
• Liver impairment: moderate to severe disease, reduce dose by about 50% or extend the interval.
• Region: widely available in East Africa; community MRSA is increasing, so clindamycin is a frequent oral option for skin infection.

Preparation. Oral capsules with a full glass of water, swallowed upright. IV: dilute to 18 mg/mL or less and infuse over 10 to 60 minutes; no faster than 30 mg/min and no more than 1.2 g in an hour; never as a bolus.

Baseline and monitoring

• Baseline: medication review, liver tests in prolonged use, stool pattern.
• During treatment: ask about diarrhoea at each review; liver tests and full blood count in courses over 3 weeks.

Stop rules. Stop for new diarrhoea (3 or more loose stools a day), blood or mucus in stool, severe rash, jaundice or anaphylaxis.

Referral and escalation. Refer for severe or fulminant colitis, bone and joint infection, and necrotising soft tissue infection.