Calcium stones; Nephrolithiasis
Diuretics. Diuretics are medicines commonly used to treat high blood pressure and other disorders. They remove fluid and sodium from the body. Low doses of a class of diuretics known as thiazides are sometimes used to reduce the amount of calcium kidneys release into the urine. Thiazides include:
However, thiazides also cause potassium loss, which reduces citrate levels and can increase the risk for stones. Patients taking thiazide pills should also take potassium citrate, to prevent citrate loss. Amiloride (Midamor) is a potassium-sparing diuretic, which may be used if a thiazide does not work.
Citrates. Citrate salts are often given to people with calcium oxalate or uric acid stones:
People with struvite stones, urinary tract infections, bleeding disorders, or kidney damage should not use these products. Patients who take citrate supplements containing potassium should not take any other medications that either contain this mineral or prevent its loss (such as so-called potassium-sparing diuretics). People with peptic ulcers should avoid citrate supplements, or discuss using non-tablet forms with their doctor.
Phosphates. Phosphates help reduce the breakdown of bone that releases calcium into the bloodstream. They are also involved in the kidney's reabsorption of calcium from the urine.
Avoid acidic forms of phosphate, since they increase the risks for both hypocitraturia and hypercalciuria.
Cholestyramine (such as Questran and Questran Light) is a drug used to reduce cholesterol levels. However, it also binds with oxalate in the intestine, so it is also used to reduce high oxalate levels in urine (hyperoxaluria). The drug usually comes in a powder that is dissolved in liquid. Bloating and constipation are common side effects of this drug. Cholestyramine also interferes with other medications, including digoxin (Lanoxin) and warfarin, and may contribute to calcium loss and osteoporosis. In order to prevent such interactions, take other drugs 1 hour before, or 4 - 6 hours after, taking cholestyramine.
Long-term use of cholestyramine may cause deficiencies of vitamins A, D, E, and K. Vitamin supplements may be necessary.
Sodium Bicarbonate. Patients whose persistently acidic urine causes uric acid stones may take sodium bicarbonate to reduce urine acidity. Patients taking sodium bicarbonate must test their urine regularly with pH paper, which turns different colors depending on whether the urine is acidic or alkaline. Too much sodium bicarbonate can cause the urine to become too alkaline. This increases the risk for calcium phosphate stones. Patients who need to reduce the amount of sodium they take in (as a result of other medical conditions) should not use sodium bicarbonate.
Potassium Citrate. Potassium citrate, which restores citrate to the urine, is useful for patients with high levels of uric acid in the urine.
Allopurinol. Allopurinol (Lupurin, Zyloprim) is very effective in reducing high blood levels of uric acid, and may be helpful for patients with uric acid stones. Allopurinol will not prevent calcium stones from forming. There is also a slight risk for the formation of xanthine stones with this drug. Side effects include diarrhea, headache, and fever. About 2% of patients have an allergic reaction to allopurinol that causes a rash. In rare cases, the rash can become severe and widespread enough to be life threatening.
Allopurinol reduces uric acid levels rapidly, so it may trigger an attack of gout in vulnerable people. To prevent this problem, patients taking allopurinol should also take a nonsteroidal anti-inflammatory drug (NSAID) for 2 or 3 months. Aspirin should not be taken, since it increases uric acid levels. Patients should discuss the appropriate NSAID choice with their doctor.
In 2009, the U.S. Food and Drug Administration approved febuxostat (Uloric) to treat gout. It is the first new treatment for gout in 40 years. Febuxostat lowers uric acid levels by inhibiting the same enzyme as allopurinol, and can be taken by patients who are allergic to allopurinol. This new drug is very effective but expensive.
Before patients can receive any medical treatment for struvite stones, they must have surgery to completely remove the stones.
Antibiotics for Eliminating Infection. People with struvite stones receive ongoing treatment with antibiotics to keep the urine free of the bacteria that cause urinary tract infections. Careful follow-up and urine testing is extremely important. A high-pH urine indicates low acidity and an increased risk of infection.
Acetohydroxamic Acid (AHA). Acetohydroxamic acid (AHA or Lithostat) is beneficial when used with long-term antibiotics. AHA blocks enzymes that bacteria release, and has been effective in preventing stones even when bacteria are present. Side effects, however, can be severe. The drug reduces iron levels in the body, so anemia is a common problem. Patients may need to take iron supplements. Other side effects include nausea, vomiting, depression, anxiety, rash, persistent headache, and, rarely, small blood clots in the legs. This drug is recommended only for patients with healthy kidneys who have chronic diseases caused by specific struvite-causing organisms. Patients taking this medicine should avoid alcohol. Pregnant women should not take acetohydroxamic acid.
Organic Acids. Medical treatments to dissolve stones may be useful in patients who do not respond to other medications, or in combination with surgeries. Acidic urine dissolves struvite stones, so the doctor may wash the urinary tract with a solution of organic acids (such as Renacidin). Candidates for such washes must have sterile urine (no bacteria or other organisms in the urine) and healthy kidney function. In surgical patients, the wash is performed 4 or 5 days after the operation. The wash starts with saline (salt solution) for 1 - 2 days and, if there are no problems, the organic acid solution follows for another 1 or 2 days, until all stones dissolve. Regular urine tests are necessary to ensure that the bacteria do not return.
Aluminum Hydroxide Gel. An aluminum hydroxide anti-acid gel may reduce phosphate levels that are important in struvite stone formation, but it has a long-term risk of causing aluminum toxicity. Long-term reduction of phosphorus can also increase the risk for calcium oxalate stones. Experts recommend limiting phosphorus through a low-protein diet, rather than through the use of this gel.
The first-line treatment for cystine stones is increasing the alkalization of urine so the stones can dissolve. If alkalization fails, drug treatments may include d-penicillamine, alpha-mercaptopropionylglycine (tiopronin), or captopril. These medications lower cystine concentration.
Patients with cystine stones must drink much more fluids than patients with other stones -- at least 4 quarts of water over a 24-hour period.
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