Colchicine
Colchicine binds tubulin and disrupts the microtubules that white blood cells need in order to move and pile into an inflamed joint. That interruption of the inflammatory response is what quietens a gout attack and what prevents flares while urate-lowering treatment is being established. It does not lower uric acid itself.
Colchicine has a narrow safety window, meaning the gap between an effective amount and a toxic one is small, so anything that raises its blood level matters. Grapefruit is avoided, and clarithromycin and atorvastatin both interfere with its clearance, the statin combination also raising the risk of muscle injury. White cells are monitored because colchicine can suppress the marrow, creatinine because impaired kidneys let the drug accumulate, and vitamin B12 because absorption in the gut is blocked with prolonged use.
Diarrhoea is the first sign of too much colchicine and is a reason to stop and call a doctor rather than push on. Vomiting, unexplained muscle pain or weakness, numbness or tingling, or fever and sore throat suggesting a low white cell count all mean see a doctor.
Reference information, not medical advice. Discuss any change with your doctor.