Gout is a disease where there is excess uric acid in the body and it is deposited as crystals at the joint. Normally, this deposition will occurred at the joints which located at the lower parts of the body such as thumb of the feet due to gravity force. Once, this disease is known as “the disease of the kings” because it only occurs among the one whom wealthy. The main reason for this disease to be nickname so is because of the causes of the disease. The excess uric acid in the body can be caused by increase in production of uric acid by the body itself. Certain meats, seafood, dried peas and beans are purines-rich meals which contribute to the increase of production of uric acid by the body. Besides that, alcohol also can increase uric acid and precipitate in gout attacks. Being overweight increases the risk of gout because there is more tissue available for turnover or breakdown, which leads to excess uric acid production. As treatment, allopurinol will be given to the patient.
When excess uric acid is produced in the body, the level of uric acid in the blood will be elevated and the uric acid will deposits around the joints such as the thumb of the feet. Normally, the deposit will be in sharp needle-like crystal of monosodium urate. Uric acid also can collect under the skin as tophi, or in the urinary tract as kidney stones. Usually when gout attacks, patient will have the symptoms such as redness, heat, swelling, and pain in joints. Therefore, allopurinol will be prescribed to patient who had gout attacks.
Allopurinol is a structural analog or isomer of the natural purine base, hypoxanthine. Allopurinol can be found in the form of tablets for the patients. With the present of enzyme, xanthine oxidase, hypoxanthine and xanthine can be metabolize to uric acid. If this process out of control, the level of uric acid in the blood will be elevated, causing it to deposit at the joint. Allopurinol inhibits the enzyme xanthine oxidase. Therefore, the level of the uric acid in the blood can be lowered. In addition to blocking uric acid production, inhibition of xanthine oxidase causes an increase in production of hypoxanthine and xanthine, which are converted to closely related purine ribotides adenosine and guanosine monophosphates. Increased levels of these ribotides causes feedback inhibition of amidophosphoribosyl transferase, the first and rate-limiting enzyme of purine biosynthesis. This feedback is a negative feedback which indirectly inhibits purine biosynthesis. Allopurinol therefore decreases both uric acid formation and purine synthesis.