* 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
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