Effect in Gout

Colchicine does not influence the renal excretion of uric acid or its concentration in blood. By virtue of its ability to bind to tubulin, colchicine interferes with the function of the mitotic spindles and causes depolymerization and disappearance of the fibrillar microtubules in granulocytes and other motile cells. This action is apparently the basis for the beneficial effect of colchicine, namely, the inhibition of the migration of granulocytes into the inflamed area and a decreased metabolic and phagocytic activity of granulocytes. This reduces the release of lactic acid and proinflammatory enzymes that occurs during phagocytosis and breaks the cycle that leads to the inflammatory response. 

Neutrophils exposed to urate crystals ingest them and produce a glycoprotein, which may be the causative agent of acute gouty arthritis. Injected into joints, this substance produces a profound arthritis that is histologically indistinguishable from that caused by direct injection of urate crystals. Colchicine appears to prevent the elaboration by leukocytes of this glycoprotein. 

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Replacement of the methyl ketone moiety in 78 by a phenyl sulfoxide, interestingly, leads to a relatively potent uricosuric agent with diminished antiinflammatory action. This effect in lowering serum levels or uric acid leads to the use of this drug in the treatment of gout. Alkylation of diethyl malonate with the chlorosulfide, 79, gives the intermediate, 80. The pyrazolodione (81) is prepared in the usual way by condensation with hydrazobenzene. Careful oxidation of the sulfide with one equiv-... 

As an inhibitor of xanthine oxidase, allopurinol also markedly decreases oxidation of both hypoxanthine and xanthine itself to the sole source of uric acid (19) in man. This metabolic block thus removes the source of uric acid that in gout causes the painful crystalline deposits in the joints. It is of interest that allopurinol itself is oxidized to the somewhat less effective drug, oxypurinol (21), by xanthine oxidase. 

In addition, the alkaloid colchicine (from Colchicum autumnale) blocks tubulin polymerization by binding to heterodimeric (3-tubulin between amino acids 239 and 254. Since it inhibits the MT-dependent migration of granulocytes into areas of inflammation and their MT-dependent release of proinflammatory agents, it is used to treat attacks of gout. Its antimitotic effect in the gastrointestinal system induces diarrhoea. Nocodazole competes for the binding site of colchicine and has similar effects on heterodimeric (3-tubulin. 

Xanthine oxidase (XO) is not only an important biological source of ROS but also the enzyme responsible for the formation of uric acid associated with gout leading to painful inflammation in the joints. The XO inhibition effect by the enzymatically synthesized poly(catechin) increased as an increasing concentration of catechin units, while the monomeric catechin showed almost negligible inhibition effect in the same concentration range. ° This markedly amplified XO inhibition activity of poly(catechin) was considered to be due to effective multivalent interaction between XO and the condensed catechin units in the poly (catechin). 

Colchicine is an antimitotic drug that is highly effective in relieving acute gout attacks but has a low benefit-toxicity ratio. When colchicine is started within the first 24 hours of an acute attack, about two-thirds of patients respond within several hours. The likelihood of success decreases substantially if treatment is delayed longer than 48 hours after symptom onset. 

Renal impairment - Some degree of renal impairment may be present in patients with gout. A daily dosage of 1 g may be adequate. However, if necessary, the daily dosage may be increased by 0.5 g increments every 4 weeks within tolerance (usually not more than 2 g/day) if symptoms of gouty arthritis are not controlled or the 24 hour urate excretion is not more than 700 mg. Probenecid may not be effective in chronic renal insufficiency, particularly when the glomerular filtration rate is 30 mL/minute or less. 

Pharmacoiogy The exact mechanism of action of colchicine in gout is not known. Colchicine apparently exerts its effect by reducing the inflammatory response to the deposited crystals and also by diminishing phagocytosis. Colchicine diminishes lactic acid production by leukocytes directly and by diminishing phagocytosis and thereby interrupts the cycle of urate crystal deposition and inflammatory response that sustains the acute attack. 

Pharmaceutical therapy of acute arthritis of crystal-deposition disease is effective, in particular for gout and hyperuricemia. Treatment is directed towards termination of acute arthritis, prevention of recurring attacks and prophylaxis and reversal of complications of chronic gout. Such complications include tophi, urolithiasis, nephropathy and with hyperuricemia associated medical problems that can be prevented, inhibited, and sometimes reversed. 

Colchicine, an alkaloid obtained from the autumn crocus, has long been used and is relatively selective for the treatment of acute gouty arthritis. Unlike many of the newer agents for use in gout, colchicine has minimal effects on uric acid synthesis and excretion it decreases inflammation associated with this disorder. It is thought that colchicine somehow prevents the release of the chemotactic factors and/or inflammatory cytokines from the neutrophils, and this in turn decreases the attraction of more neutrophils into the affected area (Fig. 37.1).The ability of colchicine to bind to leukocyte microtubules in a reversible covalent complex and cause their depolymerization also may be a factor in decreasing the attraction of the motile leukocytes into the inflamed area. 

The major use of colchicine is as an antiinflammatory agent in the treatment of acute gouty arthritis it is not effective in reducing inflammation in other disorders. It also can be used to prevent attacks. Since colchicine is so rapidly effective in relieving the acute symptoms of gout (substantial improvement is achieved within hours), it has been used as a diagnostic aid in this disorder. 

Nucleotides and nucleosides have emerged as important molecules in medicinal chemistry. In the 1950s, Elion and Hitchings discovered that 6-mercaptopurine had antitumor properties. This pioneering discovery opened the door for many subsequent studies of nucleotide derivatives as therapeutics. Acyclovir (8.3), a nucleoside that lacks two carbon atoms of its ribose ring, is effective in the treatment of herpes infections. Allopurinol, a purine derivative, is useful in the treatment of gout. 

Treatment of gout In large dose, aspirin is effective in the treatment of gout. 

It is effective for treatment of acute attacks of gout. It has no effect on renal excretion of uric acid. It binds to tubulin, it interferes with function of mitotic spindles, causes depolymerization and disappearance of fibrillar microtubules in granulocytes. In gout, the useful of colchicine is due to the inhibition of the release of glycoproteins from granulocytes in inflamed joint thus preventing precipitation of uric acid crystals and release of lysosomal enzymes. 

The NSAIDs have a number of commonalities. Although not all NSAIDs are approved by the FDA for the whole range of rheumatic diseases, most are probably effective in rheumatoid arthritis, seronegative spondyloarthropathies (eg, psoriatic arthritis and arthritis associated with inflammatory bowel disease), osteoarthritis, localized musculoskeletal syndromes (eg, sprains and strains, low back pain), and gout (except tolmetin, which appears to be ineffective in gout). 

AccessMedicine Print Chapter 36. Nonsteroidal Anti-Inflammatory Drugs, Disease-Modifying Antirheumatic Drugs, Nonopioid Analgesics, Drugs Used in Gout Acute pain and fever may be effectively treated with 325-500 mg four times daily and proportionately less for children. 

Although colchicine is more specific in gout than the NSAIDs, NSAIDs (eg, indomethacin and other NSAIDs [except aspirin]) have replaced it in the treatment of acute gout because of the troublesome diarrhea sometimes associated with colchicine therapy. Colchicine is now used for the prophylaxis of recurrent episodes of gouty arthritis, is effective in preventing attacks of acute Mediterranean fever, and may have a mild beneficial effect in sarcoid arthritis and in hepatic cirrhosis. Although it can be given intravenously, this route should be used cautiously because of increased bone marrow toxicity. 

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