Allopurinol

How it works

     * Allopurinol may be used to decrease levels of uric acid in people
       with gout, kidney stones, or who are receiving certain types of
       chemotherapy.
     * Allopurinol reduces the production of uric acid (a compound
       produced by the body associated with gout and kidney stones), by
       inhibiting an enzyme called xanthine oxidase. Allopurinol reduces
       levels of uric acid in the blood and the urine.
     * Allopurinol belongs to the class of medicines called xanthine
       oxidase inhibitors.

Upsides

     * May be used to prevent acute attacks of gout and to reduce ongoing
       complications of gout such as tophi (deposits of crystalline uric
       acid that form painful nodules), joint destruction, uric acid
       lithiasis (the formation of kidney or bladder stones), and kidney
       disease. Note that allopurinol does not treat acute attacks of
       gout, although once started, it should be continued throughout an
       acute attack.
     * May be used temporarily to reduce elevated uric acid levels caused
       by certain cancer treatments in people with leukemia, lymphoma, and
       other malignancies.
     * May also be used to treat recurrent kidney stones (calcium oxalate
       calculi) in males with a urinary uric acid level of more than 800
       mg/day, or in females with levels greater than 750 mg/day. The need
       for continued treatment should be reassessed periodically.
     * Available as an oral tablet and as an injection.
     * Can be taken once a day.
     * Generic allopurinol is available.

Downsides

   If you are between the ages of 18 and 60, take no other medication or
   have no other medical conditions, side effects you are more likely to
   experience include:
     * May cause a skin rash which may be a sign of an allergic reaction
       to allopurinol. This is considered a serious event and allopurinol
       should be discontinued immediately and urgent medical advice
       sought. People with kidney disease who are receiving thiazide
       diuretics in addition to allopurinol are considered at higher risk.
     * May precipitate gout attacks during the early stages of
       administration, even when uric acid levels are normal.
       Coadministration with colchicine or an anti-inflammatory agent is
       recommended initially, in addition to gradually increasing the
       dosage of allopurinol.
     * May also cause diarrhea, nausea, and laboratory test changes.
     * Occasionally may cause drowsiness. Affected people should not drive
       or operate machinery.
     * May interact with a number of different drugs including
       mercaptopurine and azathioprine (the dosage of these two drugs
       needs to be reduced to approximately one-third to one-fourth of
       their normal dosage).
     * Rarely, may cause reversible liver damage or elevations in liver
       enzymes. Monitoring is necessary for people with pre-existing liver
       disease and an investigation into the functioning of the liver
       should be conducted if symptoms such as weight loss or itchy skin
       develop.
     * Rarely, may cause bone marrow depression. May occur anywhere from 6
       weeks to years after administration of allopurinol and the risk is
       greatest in those receiving other drugs that also have the
       potential to cause bone marrow depression.
     * The dosage of allopurinol needs reducing in people with kidney
       disease and their renal function monitored at least during the
       early stages of therapy. People administered allopurinol for high
       uric acid levels occurring as a result of cancer are at higher risk
       of developing kidney damage from allopurinol.

   Notes: In general, seniors or children, people with certain medical
   conditions (such as liver or kidney problems, heart disease, diabetes,
   seizures) or people who take other medications are more at risk of
   developing a wider range of side effects. For a complete list of all
   side effects, [84]click here.

Bottom Line

   Allopurinol is used in the treatment of high uric acid levels
   associated with gout, kidney stones, and cancer treatment. If a rash
   occurs while taking allopurinol, immediate discontinuation of
   allopurinol is required and urgent medical advice should be sought.

Tips

     * Allopurinol may be better tolerated if taken with food.
     * If you forget a dose of allopurinol, you do not need to double up
       the next dose. Just continue taking allopurinol as scheduled.
     * Discontinue allopurinol at the first appearance of a skin rash,
       painful urination, blood in the urine, eye irritation, or facial
       swelling and seek urgent medical advice.
     * Allopurinol is a maintenance treatment for gout or high uric acid
       levels so should be taken regularly even once a gout attack has
       resolved. Other treatments (such as NSAIDs or colchicine) are
       usually prescribed to be taken during an acute gout attack.
     * Seek immediate medical advice if unexplained weight loss or
       itchiness develop while you are taking allopurinol.
     * Do not drive or operate machinery if allopurinol makes you drowsy
       or impairs your judgment.
     * Ensure you maintain a good intake of fluid while taking
       allopurinol. A fluid intake of 2 liters per day is recommended to
       reduce the risk of kidney stones developing.

Response and Effectiveness

     * Peak levels of allopurinol are reached within 1.5 hours and 4.5
       hours for its active metabolite. Allopurinol may be taken once
       daily.
     * Normal serum uric acid levels are normally achieved within one to
       three weeks.
     * It may take two to six weeks before allopurinol effectively reduces
       gout attacks. It is not unusual to experience a gout attack in the
       first few weeks of allopurinol initiation.
     * In people with severe kidney disease, a dosage of 100 mg/day or
       300mg twice a week may be sufficient to reduce high uric acid
       levels.

References