Colchicine

Colchicine is a highly poisonous alkaloid, originally extracted from plants of the genus Colchicum (autumn crocus, meadow saffron) with the chemical formula C₂₂H₂₅NO₆. Originally used to treat rheumatic complaints and especially gout, it was also prescribed for its cathartic and emetic effects. Its present use is mainly in the treatment of gout.

History

The colchicine alkaloid was first isolated in 1820 by the two French chemists P.S. Pelletier and J. Caventon (Pelletier PS, Caventon J. Ann. Chim. Phys. 1820;14:69).

Colchicum extract was first described as a treatment for gout in De Materia Medica of Padanius Dioscorides.

It was later identified as a tricyclic alkaloid and its pain relieving and anti-inflammatory effects for gout were linked to it binding with the protein tubulin.

Pharmacology

Biological function

The molecular formula of colchicine is C₂₂H₂₅NO₆. Name is N-[(7S)-5,6,7,9-tetrahydro-1,2,3,10-tetramethoxy-9-oxobenzo[a]heptalen-7-yl)acetamide].

It inhibits the cytoskeleton by binding to tubulin, one of the main constituents of microtubules. Apart from inhibiting mitosis, a process heavily dependent on cytoskeletal changes, it also inhibits neutrophil motility and activity, leading to a net anti-inflammatory effect.

Colchicine as medicine

Colchicine is FDA-approved for the treatment of gout and also for familial Mediterranean fever, amyloidosis, and scleroderma. Side-effects include gastro-intestinal upset and neutropenia. Starting the drug early during an attack of gout can exacerbate the symptoms. High doses can also damage bone marrow and lead to anemia. It's not used in the treatment of cancer, as the dose required would lead to intolerable side-effects.

Toxicity

Poisoning resembles intoxication with arsenic: symptoms start 2 to 5 hours after the toxic dose has been ingested and include burning in the mouth and throat, fever, vomiting, diarrhea, abdominal pain and kidney failure. Death from respiratory failure can follow. There is no antidote.

Laboratory use

In laboratory setting colchicine is also used for inducing polyploidy in plant cells during cellular division.

External links

• Feature on colchicine
• Pharmacology of colchicine