uric acid levels). Dosage is adjusted to maintain a reduced urinary excretion of uric acid. Serum uric acid level at or below 6 mg/100 mL is often a therapeutic goal. Hyperuricemia is not necessary for the formation of uric acid stones; hyperuricosuria can occur in the presence of normal or even low serum uric acid. Some practitioners advocate adding allopurinol only in people in whom hyperuricosuria and hyperuricemia persist, despite the use of a urine-alkalinizing agent such as sodium bicarbonate or potassium citrate. Treatment Stone size influences the rate of spontaneous stone passage. For example, up to 98% of small stones (less than in diameter) may pass spontaneously through urination within four weeks of the onset of symptoms, but for larger stones ( in diameter), the rate of spontaneous passage decreases to less than 53%. Initial stone location also influences the likelihood of spontaneous stone passage. Rates increase from 48% for stones located in the proximal ureter to 79% for stones located at the vesicoureteric junction, regardless of stone size. Assuming no high-grade obstruction or associated infection is found in the urinary tract, and symptoms are relatively mild, various nonsurgical measures can be used to encourage the passage of a stone. Repeat stone formers benefit from more intense management, including proper fluid intake and use of certain medications, as well as careful monitoring. Pain management Management of pain often requires intravenous administration of NSAIDs or opioids. NSAIDs appear somewhat better than opioids or paracetamol in those with normal kidney function. Medications by mouth are often effective for less severe discomfort. The use of antispasmodics does not have further benefit. Medical expulsive therapy The use of medications to speed the spontaneous passage of stones in the ureter is referred to as medical expulsive therapy. Several agents, including alpha adrenergic blockers (such as tamsulosin) and calcium channel blockers (such as nifedipine), may be effective. Alpha-blockers likely result in more people passing their stones, and they may pass their stones in a shorter time. People taking alpha-blockers may also use less pain medication and may not need to visit the hospital. Alpha-blockers appear to be more effective for larger stones (over 5 mm in size) than smaller stones. However, use of alpha-blockers may be associated with a slight increase in serious, unwanted effects from this medication. A combination of tamsulosin and a corticosteroid may be better than tamsulosin alone. These treatments also appear