From the Guidelines
Allopurinol therapy should be monitored with baseline and periodic assessment of renal function, liver function tests, complete blood count, and serum uric acid levels, with a target serum uric acid level of <6 mg/dL, as recommended by the 2020 American College of Rheumatology guideline for the management of gout 1. When initiating allopurinol therapy, it is essential to obtain baseline serum creatinine, BUN, liver enzymes (ALT, AST), CBC, and uric acid levels.
- During the first few months of treatment, these parameters should be checked every 2-4 weeks,
- then every 3-6 months once stable,
- with serum uric acid levels monitored until the target level is achieved,
- and patients should be monitored for hypersensitivity reactions, particularly during the first 8 weeks of therapy,
- as allopurinol can cause severe cutaneous adverse reactions (SCARs) including Stevens-Johnson syndrome,
- and dose adjustments may be necessary in patients with renal impairment,
- as allopurinol and its metabolite oxypurinol are primarily excreted by the kidneys,
- and patients should also be assessed for potential drug interactions,
- particularly with azathioprine, mercaptopurine, and warfarin,
- as allopurinol can increase the effects of these medications,
- and the 2014 multinational evidence-based recommendations for the diagnosis and management of gout also support the use of allopurinol as the first-line urate-lowering therapy,
- with a low starting dose and escalation to achieve a target serum urate level,
- and monitoring of serum urate level, frequency of gout attacks, and tophi size 1. Regular monitoring is crucial to ensure the safe and effective use of allopurinol,
- and to minimize the risk of adverse reactions and drug interactions,
- and the 2020 American College of Rheumatology guideline provides the most recent and highest-quality evidence for the management of gout,
- and should be followed in clinical practice to optimize patient outcomes,
- in terms of morbidity, mortality, and quality of life 1.
From the FDA Drug Label
The correct dosage and schedule for maintaining the serum uric acid within the normal range is best determined by using the serum uric acid as an index. In patients with pre-existing liver disease, periodic liver function tests are recommended during the early stages of therapy In patients with decreased renal function or who have concurrent illnesses which can affect renal function such as hypertension and diabetes mellitus, periodic laboratory parameters of renal function, particularly BUN and serum creatinine or creatinine clearance, should be performed and the patient’s dosage of allopurinol tablets reassessed
The recommended monitoring parameters for allopurinol therapy include:
- Serum uric acid levels to determine the correct dosage and schedule
- Liver function tests in patients with pre-existing liver disease
- Renal function parameters, including:
- BUN
- Serum creatinine
- Creatinine clearance in patients with decreased renal function or concurrent illnesses that can affect renal function, such as hypertension and diabetes mellitus 2
From the Research
Monitoring Parameters for Allopurinol Therapy
When monitoring allopurinol therapy, several laboratory tests should be checked regularly to assess the efficacy and safety of the treatment. These include:
- Serum uric acid levels: to evaluate the effectiveness of allopurinol in lowering uric acid levels 3, 4, 5
- Serum creatinine levels: to monitor renal function and potential kidney damage 3, 6, 7
- Glomerular filtration rate (GFR): to assess kidney function and potential changes in renal function 6, 7
- Blood pressure: to monitor potential changes in blood pressure and cardiovascular risk 3, 7
- Complete blood count (CBC): to monitor for potential hematologic adverse effects 3
- Liver function tests: to monitor for potential liver damage 4
Renal Function Monitoring
Renal function should be closely monitored in patients taking allopurinol, especially those with pre-existing kidney disease. This includes:
- Regular measurement of serum creatinine levels and GFR 3, 6, 7
- Monitoring for signs of kidney damage or disease progression, such as increased proteinuria or hematuria 7
- Adjustment of allopurinol dosage as needed to minimize the risk of kidney damage 4, 5
Other Considerations
Other laboratory tests may be necessary to monitor for potential adverse effects of allopurinol, such as: