Colchicine

How it works

It binds tubulin and disrupts microtubule polymerisation, thereby impairing neutrophil chemotaxis, adhesion and degranulation and suppressing inflammasome-driven inflammation.

Prescribing in practice

• Colchicine has a narrow therapeutic index and is potentially fatal in overdose, with no specific antidote, so the prescribed regimen must never be exceeded.
• Toxicity is greatly increased by strong CYP3A4 or P-glycoprotein inhibitors (e.g. clarithromycin, ciclosporin, some antifungals) and dose reduction or avoidance is required.
• The dose must be reduced in significant renal or hepatic impairment because accumulation precipitates marrow suppression and neuromyopathy.

Monitoring

Monitor the full blood count and renal and hepatic function periodically, and review promptly if gastrointestinal symptoms, myopathy or cytopenias emerge.

Counselling the patient

• Stop the drug and seek urgent advice if you develop diarrhoea, vomiting or muscle weakness, as these can signal toxicity.
• Never take more than the prescribed amount and keep it well out of reach of children.
• Avoid grapefruit juice and tell any prescriber you are taking colchicine before starting new medicines.

Evidence & guidelines

Use in neutrophilic dermatoses is supported by long clinical experience and small studies rather than large randomised trials, and most dermatological indications are unlicensed.