From the Guidelines
Allopurinol is associated with several side effects, most commonly a rash, which can be severe in some cases, and other adverse effects such as gastrointestinal issues, drowsiness, and liver function abnormalities, as reported in a high-quality study published in the Annals of Internal Medicine 1. The most common adverse event with allopurinol is rash, and most of the serious adverse effects associated with the drug are rare, mild, and reversible; however, fatal hypersensitivity reactions have also been reported with the drug. Some key points to consider when prescribing allopurinol include:
- The risk of serious adverse effects is increased in persons with the HLA-B*5801 haplotype, which is prevalent in Asian persons and in Korean persons with stage 3 or worse chronic kidney disease, as noted in the study 1.
- Gastrointestinal issues such as abdominal pain, diarrhea, and musculoskeletal pain are also common adverse events associated with allopurinol.
- Liver function abnormalities can develop, ranging from mild enzyme elevations to hepatitis, and blood disorders including reduced white blood cell count, reduced platelet count, or aplastic anemia occur rarely.
- Allopurinol can also cause kidney problems, particularly in patients with pre-existing kidney disease. To minimize side effects, allopurinol should be started at a low dose (typically 100mg daily) and gradually increased while monitoring for adverse reactions, and patients with kidney impairment need lower doses, as suggested by the evidence 1. It is essential for patients to be aware of the potential side effects of allopurinol and to seek medical attention immediately if they experience any severe reactions, such as a rash, as this could indicate a serious reaction, as reported in the study 1.
From the FDA Drug Label
Data upon which the following estimates of incidence of adverse reactions are made are derived from experiences reported in the literature, unpublished clinical trials and voluntary reports since marketing of allopurinol tablets began The most frequent adverse reaction to allopurinol tablets is skin rash. Skin reactions can be severe and sometimes fatal Most Common Reactions* Probably Causally Related: Gastrointestinal: Diarrhea, nausea, alkaline phosphatase increase, SGOT/SGPT increase. Metabolic and Nutritional: Acute attacks of gout. Skin and Appendages: Rash, maculopapular rash Incidence Less Than 1% Probably Causally Related: Body As a Whole: Ecchymosis, fever, headache. Cardiovascular: Necrotizing angiitis, vasculitis
The side effects of allopurinol include:
- Gastrointestinal: diarrhea, nausea, alkaline phosphatase increase, SGOT/SGPT increase
- Metabolic and Nutritional: acute attacks of gout
- Skin and Appendages: rash, maculopapular rash
- Body As a Whole: ecchymosis, fever, headache
- Cardiovascular: necrotizing angiitis, vasculitis The most frequent adverse reaction is skin rash, which can be severe and sometimes fatal 2
From the Research
Side Effects of Allopurinol
The side effects of allopurinol are varied and can range from mild to severe. Some of the common side effects include:
- Maculopapular rashes
- Hives
- Itching
- Headache
- Dizziness
- Abnormal hair loss
- Fever
- Hypersensitivity reaction 3
Severe Side Effects
In some cases, allopurinol can cause severe side effects, such as:
- Stevens-Johnson syndrome (SJS), a life-threatening severe cutaneous adverse reaction 4
- Toxic epidermal necrolysis syndrome
- Drug-induced meningitis, which can lead to a reduced state of consciousness 3
- Acute renal failure and hemodynamic compromise 4
Comparison with Other Medications
Studies have compared the safety and efficacy of allopurinol with other medications, such as febuxostat. One study found that febuxostat had a similar safety profile to allopurinol, but with a higher frequency of gout attacks induced by the sudden reduction in blood uric acid levels during the early treatment period 5.
Special Considerations
Allopurinol can be used to treat a range of conditions, including gout, hyperuricemia, and uremic kidney stones. However, its use may be associated with various adverse effects, and patients should be closely monitored for any signs of side effects 6, 7.