Several drugs may precipitate in the urine as crystals, which can result in renal tubular obstruction and acute renal failure. The risk of crystal formation is increased if certain factors are present.


Drugs associated with crystal formation and acute renal failure:

(1) acyclovir (aciclovir)

(2) ciprofloxacin (uncommon)

(3) foscarnet (uncommon)

(4) indanavir

(5) methotrexate

(6) sulfonamides

(7) triamterene

(8) vitamin C (uncommon)


Risk factors:

(1) reduced urine perfusion and urine formation, with concentrated urine

(1a) true volume depletion (dehydration from diarrhea, vomiting, renal salt wasting, adrenal insufficiency, excessive insensitive fluid loss)

(1b) fluid sequestration (pancreatitis, ascites, effusions)

(1c) heart failure

(1d) capillary leak syndrome

(2) pre-existing renal dysfunction

(3) excessive drug dosing, with high plasma and urine drug levels

(4) urine pH resulting in decreased solubility

(4a) precipitate in acid urine: methotrexate, sulfonamide, triamterene

(4b) precipitate in alkaline urine: indinavir


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