Lincomycin

Lincomycin is the parent lincosamide, used as an alternative to clindamycin where clindamycin is unavailable. It has weaker activity and the same risk of Clostridioides difficile infection, so its use has largely ended in many countries.

Classification. Lincosamide.

Mechanism. Binds the 50S ribosomal subunit and blocks protein synthesis; bacteriostatic.

Spectrum. Staphylococcus aureus (non-resistant strains), streptococci, pneumococci and some anaerobes. Activity is lower than clindamycin and cross-resistance with macrolides and clindamycin is complete. Not active against Gram-negative aerobes or enterococci.

Pharmacokinetics. Oral bioavailability only 20 to 35%, reduced by food. Half-life 4 to 6 hours. Good bone penetration; poor CSF penetration. Hepatic metabolism with biliary and renal excretion.

Maximum 8 g daily (parenteral).

Adults.

• Oral: 500 mg every 6 to 8 hours, taken 1 hour before or 2 hours after food (maximum 2 g daily in many labels).
• IM: 600 mg every 12 to 24 hours.
• IV: 600 mg to 1 g every 8 to 12 hours in severe infection.
• Skin and soft tissue infection, respiratory infection in penicillin allergy: 500 mg orally every 6 to 8 hours for 5 to 10 days.
• Bone and joint infection: IV 600 mg to 1 g every 8 hours, then oral to complete 6 weeks or longer by site.

Children over 1 month. Oral 30 to 60 mg/kg/day divided every 6 to 8 hours; IM 10 mg/kg every 12 to 24 hours; IV 10 to 20 mg/kg/day divided every 8 to 12 hours.

Alternatives. Clindamycin, doxycycline, amoxicillin clavulanate, trimethoprim sulfamethoxazole.

Boxed-warning level risk. Clostridioides difficile infection, which can be fatal.

Contraindications. Lincosamide hypersensitivity; infants under 1 month; previous Clostridioides difficile colitis (relative).

Adverse effects. Diarrhoea, nausea, vomiting, rash, glossitis, IM injection site pain. Serious: Clostridioides difficile colitis, severe skin reactions, hepatic injury, neutropenia, hypotension and cardiopulmonary arrest with rapid IV infusion.

Interactions. Neuromuscular blockers (prolonged block); erythromycin (antagonism); kaolin-pectin (reduced absorption: separate by 2 hours).

Common prescribing errors. Rapid IV infusion, giving with food, and treating minor infection.

Special groups. - Pregnancy: use only when necessary. Breastfeeding: avoid if possible (excreted in milk). - Older adults: higher risk of diarrhoea and colitis; use the lowest effective dose. - Kidney impairment: reduce the dose to 25 to 30% of the usual dose in severe impairment. - Liver impairment: use with caution; reduce dose in severe disease. - Region: limited availability in East Africa.

Preparation. IV: dilute 1 g in at least 100 mL of 0.9% sodium chloride or 5% glucose and infuse over at least 1 hour; do not exceed 100 mL/h. IM: deep injection, no more than 600 mg at one site.

Baseline and monitoring. - Baseline: medication review, liver tests, stool pattern. - During treatment: ask about diarrhoea; full blood count and liver tests in courses over 3 weeks.

Stop rules. Stop for new diarrhoea, blood in stool, severe rash, jaundice or anaphylaxis.

Referral and escalation. Refer for severe colitis, bone and joint infection and treatment failure.