Colchicine

Gout Colchicine is an alternative for those unable to tolerate nonsteroidal anti-inflammatory drugs (NSAIDs) when treating gout. Low doses (1.2 mg in one hour, followed by 0.6 mg an hour later) appear to be well tolerated and may reduce gout symptoms and pain, perhaps as effectively as NSAIDs. At higher doses, side effects (primarily diarrhea, nausea, or vomiting) limit its use. adverse gastrointestinal effects may occur, though overall the risk of serious side effects is low. Risk of cardiovascular disorders In June 2023, the US FDA approved a low-dose regimen of colchicine (brand name Lodoco) to reduce the risk of further disorders in adults with existing cardiovascular diseases. As an anti-inflammatory drug, Lodoco in a dose of 0.5 mg per day reduced the rate of cardiovascular events by 31% in people with established atherosclerosis and by 23% in people with recent myocardial infarction. It appears to have limited effect in relapsing polychondritis, as it may only be useful for the treatment of chondritis and mild skin symptoms. It is a component of therapy for several other conditions, including pericarditis, pulmonary fibrosis, biliary cirrhosis, various vasculitides, pseudogout, spondyloarthropathy, calcinosis, scleroderma, and amyloidosis. Research regarding the efficacy of colchicine in many of these diseases has not been performed. Colchicine is effective for prevention of atrial fibrillation after cardiac surgery. In people with recent myocardial infarction (recent heart attack), it has been found to reduce risk of future cardiovascular events. Its clinical use may grow to include this indication. ==Contraindications==

Long-term (prophylactic) regimens of oral colchicine are absolutely contraindicated in people with advanced kidney failure (including those on dialysis). About 10–20% of a colchicine dose is excreted unchanged by the kidneys; it is not removed by hemodialysis. Cumulative toxicity is a high probability in this clinical setting, and a severe neuromyopathy may result. The presentation includes a progressive onset of proximal weakness, elevated creatine kinase, and sensorimotor polyneuropathy. Colchicine toxicity can be potentiated by the concomitant use of cholesterol-lowering drugs. ==Adverse effects==

Deaths – both accidental and intentional – have resulted from overdose of colchicine. which may include neuromuscular toxicity and rhabdomyolysis. ==Toxicity==

According to one review, colchicine poisoning by overdose (range of acute doses of 7 to 26 mg) begins with a gastrointestinal phase occurring 10–24 hours after ingestion, followed by multiple organ dysfunction occurring 24 hours to 7 days after ingestion, after which the affected person either declines into multiple organ failure or recovers over several weeks. If the affected persons survive the gastrointestinal phase of toxicity, they may experience multiple organ failure and critical illness. This includes kidney damage, which causes low urine output and bloody urine; low white blood cell counts that can last for several days; anemia; muscular weakness; liver failure; hepatomegaly; bone marrow suppression; thrombocytopenia; and ascending paralysis leading to potentially fatal respiratory failure. Neurologic symptoms are also evident, including seizures, confusion, and delirium; children may experience hallucinations. Recovery may begin within six to eight days and begins with rebound leukocytosis and alopecia as organ functions return to normal. Long-term exposure to colchicine can lead to toxicity, particularly of the bone marrow, kidney, and nerves. Effects of long-term colchicine toxicity include agranulocytosis, thrombocytopenia, low white blood cell counts, aplastic anemia, alopecia, rash, purpura, vesicular dermatitis, kidney damage, anuria, peripheral neuropathy, and myopathy. No specific antidote for colchicine is known, but supportive care is used in cases of overdose. In the immediate period after an overdose, monitoring for gastrointestinal symptoms, cardiac dysrhythmias, and respiratory depression is appropriate, and may require gastrointestinal decontamination with activated charcoal or gastric lavage. Mechanism of toxicity With overdoses, colchicine becomes toxic as an extension of its cellular mechanism of action via binding to tubulin. Cells so affected undergo impaired protein assembly with reduced endocytosis, exocytosis, cellular motility, and interrupted function of heart cells, culminating in multiple organ failure. Epidemiology In the United States, several hundred cases of colchicine toxicity are reported annually, about 10% of which end with serious morbidity or mortality. Many of these cases are intentional overdoses, but others were accidental; for example, if the drug were not dosed appropriately for kidney function. Most cases of colchicine toxicity occur in adults. Many of these adverse events resulted from the use of intravenous colchicine. It was used intentionally as a poison in the 2015 killing of Mary Yoder. == Drug interactions ==

Colchicine interacts with the P-glycoprotein transporter, and the CYP3A4 enzyme involved in drug and toxin metabolism. Fatal drug interactions have occurred when colchicine was taken with other drugs that inhibit P-glycoprotein and CYP3A4, such as erythromycin or clarithromycin. ==Pharmacology==

Mechanism of action In gout, inflammation in joints results from the precipitation of uric acid as needle-like crystals of monosodium urate in and around synovial fluid and soft tissues of joints. == History ==

The plant source of colchicine, the autumn crocus (Colchicum autumnale), was described for treatment of rheumatism and swelling in the Ebers Papyrus (circa 1500 BC), an Egyptian medical text. It is a toxic alkaloid and secondary metabolite. Colchicum extract was first described as a treatment for gout in De Materia Medica by Pedanius Dioscorides, in the first century AD. Use of the bulb-like corms of Colchicum to treat gout probably dates to around 550 AD, as the "hermodactyl" recommended by Alexander of Tralles. Colchicum corms were used by the Persian physician Avicenna, and were recommended by Ambroise Paré in the 16th century, and appeared in the London Pharmacopoeia of 1618. Colchicine was first isolated in 1820 by French chemists P. S. Pelletier and J. B. Caventou. In 1833, P. L. Geiger purified an active ingredient, which he named colchicine. It quickly became a popular remedy for gout. Its pain-relieving and anti-inflammatory effects for gout were linked to its ability to bind with tubulin. The full synthesis of colchicine was achieved by the Swiss organic chemist Albert Eschenmoser in 1959. ==Sources and uses==

Physical properties Colchicine has a melting point of . It has a molecular weight of 399.4 grams per mole. Structure Colchicine has one stereocenter located at carbon 7. The natural configuration of this stereocenter is S. The molecule also contains one chiral axis - the single bond between rings A and C. The natural configuration of this axis is aS. Although colchicine has four stereoisomers, the only one found in nature is the aS,7s configuration. Light sensitivity Colchicine is a light-sensitive compound, so needs to be stored in a dark bottle. Upon exposure to light, colchicine undergoes photoisomerization and transforms into structural isomers, called lumicolchicine. After this transformation, colchicine is no longer effective in its mechanistic binding to tubulin, so is not effective as a drug. Regulation It is classified as an extremely hazardous substance in the United States as defined in Section 302 of the U.S. Emergency Planning and Community Right-to-Know Act (42 U.S.C. 11002) and is subject to strict reporting requirements by facilities that produce, store, or use it in significant quantities. Formulations and dosing Trade names for colchicine are Colcrys or Mitigare, which are manufactured as a dark– and light-blue capsule having a dose of 0.6 mg. Colchicine is also prepared as a white, yellow, or purple pill (tablet) having a dose of 0.6 mg. However, the tropolone ring of colchicine resulted from the expansion of the tyrosine ring. Radioactive feeding experiments of C. autumnale revealed that colchicine can be synthesized biosynthetically from (S)-autumnaline. That biosynthetic pathway occurs primarily through a phenolic coupling reaction involving the intermediate isoandrocymbine. The resulting molecule undergoes O-methylation directed by S-adenosylmethionine. Two oxidation steps followed by the cleavage of the cyclopropane ring lead to the formation of the tropolone ring contained by N-formyldemecolcine. N-formyldemecolcine hydrolyzes then to generate the molecule demecolcine, which also goes through an oxidative demethylation that generates deacetylcolchicine. The molecule of colchicine appears finally after the addition of acetyl-coenzyme A to deacetylcolchicine. : Purification Colchicine may be purified from Colchicum autumnale (autumn crocus) or Gloriosa superba (glory lily). Concentrations of colchicine in C. autumnale peak in the summer, and range from 0.1% in the flower to 0.8% in the bulb and seeds. When used to induce polyploidy in plants, colchicine cream is usually applied to a growth point of the plant, such as an apical tip, shoot, or sucker. Seeds can be presoaked in a colchicine solution before planting. Since chromosome segregation is driven by microtubules, colchicine alters cellular division by inhibiting chromosome segregation during mitosis; half the resulting daughter cells, therefore, contain no chromosomes, while the other half contains double the usual number of chromosomes (i.e., tetraploid instead of diploid), and lead to cell nuclei with double the usual number of chromosomes (i.e., tetraploid instead of diploid). == References ==