Other antigout drugs

Other antigout drugs

Allopurinol is used to reduce production of uric acid, preventing gouty attacks, and colchicine is used to treat acute gouty attacks.

Pharmacokinetics

Allopurinol and colchicine take somewhat different paths through the body.

All aboard allopurinol

When given orally, allopurinol is absorbed from the GI tract. Allopurinol and its metabolite oxypurinol are distributed throughout the body except in the brain, where drug concentrations are 50%
of those found in the rest of the body. It’s metabolized by the liver and excreted in urine.

Following colchicine’s course

Colchicine is absorbed from the GI tract and is partially metabolized in the liver. The drug and its metabolites then reenter the intestinal tract through biliary secretions. After reabsorption from the intestines, colchicine is distributed to various tissues. It’s excreted primarily in stool and to a lesser degree in urine.

Pharmacodynamics

Allopurinol and its metabolite oxypurinol inhibit xanthine oxidase, the enzyme responsible for the production of uric acid. By reducing uric acid formation, allopurinol eliminates the hazards of hyperuricuria.

Migration control

Colchicine appears to reduce the inflammatory response to mono-sodium urate crystals deposited in joint tissues. Colchicine may produce its effects by inhibiting migration of white blood cells (WBCs) to the inflamed joint. This reduces phagocytosis and lactic acid production by WBCs, decreasing urate crystal deposits and reducing inflammation.

Pharmacotherapeutics

Allopurinol treats primary gout, hopefully preventing acute gouty attacks. It can be prescribed with uricosurics when smaller dosages of each drug are directed. It’s used to treat:

• gout or hyperuricemia that may occur with blood abnormalities and during treatment of tumors or leukemia
• primary or secondary uric acid nephropathy (with or without the accompanying symptoms of gout)
• patients who respond poorly to maximum dosages of uricosurics or who have allergic reactions or intolerance to uricosuric drugs (it’s also used to prevent recurrent uric acid stone formation).

Acute alert

Colchicine is used to relieve the inflammation of acute gouty arthritis attacks. If given promptly, it’s especially effective in relieving pain. In addition, giving colchicine during the first several months of allopurinol, probenecid, or sulfinpyrazone therapy may prevent the acute gouty attacks that sometimes accompany the use of these drugs.

Drug interactions

Colchicine doesn’t interact significantly with other drugs. When allopurinol is used with other drugs, the resulting interactions can be serious:

• Allopurinol potentiates the effect of oral anticoagulants.
• Allopurinol increases the serum concentrations of mercapto-purine and azathioprine, increasing the risk of toxicity.
• Angiotensin-converting enzyme inhibitors increase the risk of hypersensitivity reactions to allopurinol.
• Allopurinol increases serum theophylline levels.
• The risk of bone marrow depression increases when cyclophosphamide is taken with allopurinol.
  

  Adverse reactions to other antigout drugs

  Allopurinol and colchi-cine commonly cause nausea, vomiting, diarrhea, and intermittent abdominal pain.

  Allopurinol

  The most common adverse reaction to allo-purinol is a rash.

  Colchicine

  Prolonged administration of colchicine may cause bone marrow suppression.