ULT: Urate Lowering Therapy
Basics
ULT (urate-lowering therapy) is long-term treatment for gout. It is highly effective, in that individuals who are on ULT typically should have their gout completely eliminated. ULT is not, however, a cure. It needs to be taken indefinitely, or else the gout will return. ULT is also NOT a treatment for gout flares.
How ULT Works
ULT works by lowering the uric acid level in the blood. This is typically accomplished by taking a medication that blocks the body's production of uric acid. Less commonly, a medication that increases the excretion of uric acid in the urine is used. Uric acid deposits in joints, where it can cause gout flares, over many years and takes time to be eliminated. Therefore, goals are established for lowering a patient's blood uric acid level to a target level that optimizes its elimination. If ULT is stopped, the uric acid level will rise again and gout will return.
Urate-Lowering Therapies
There are two main types of ULT: xanthine oxidase inhibitors (XOIs) and uricosurics. XOIs block the production of uric acid, while uricosurics increase the excretion of uric acid in the urine. The most commonly used ULT is allopurinol, which is a XOI. Allopurinol is the cornerstone of ULT and is the first-line ULT for most patients. Febuxostat is another XOI that is used when allopurinol is not tolerated or is not effective. It is more expensive than allopurinol and has been associated with an increased risk of cardiovascular events and death. Uricosurics are used when XOIs are not effective or are not tolerated. Probenecid is the most commonly used uricosuric. It is less effective than allopurinol and has a higher risk of side effects.
Monitoring
ULT does require periodic lab monitoring. More frequent lab checks are required initially after starting ULT, and less frequent lab checks are required once the target uric acid level is reached and the ULT dose isn't being changed. Usually, labs are required every 4-6 weeks initially, then every 3-6 months for a year or so, and then every 6-12 months.
Typical labs that are checked are the uric acid level, the complete blood count (CBC), kidney function via creatinine, and liver function via liver enzymes. The uric acid level is what is used to titrate (i.e. adjust) the ULT dose. The CBC is checked because all the ULT treatments can rarely cause drops in cell counts. Creatinine is checked because XOI's are excreted by the kidney and need to be adjusted more slowly in patients with less-than-perfect kidney function. Uricosurics are less effective in this situation as well. LFTs (liver function tests) are checked because, as with most medications, ULT can rarely cause liver injury.
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