Methylene blue and other agents as inhibitors of calcium oxalithiasis in vivo.

Growth of calcium oxalate on an established calculus upon a zinc nucleus in the bladder of rats was studied. Animals were fed either a regular solid chow or chow containing a potential crystal inhibitor ad libitum, along with drinking water containing 0.75 per cent ethylene glycol. Chow containing 0.2 per cent methylene blue and 0.5 per cent vitamin C not only decreased the growth rate, but calculi were much softer than those in controls. Safranin O was the only other significant growth inhibitor identified. Ethylenediamonotetraacetic acid and ethylenebis (oxyethylenenitrilo)-tetraacetic acid transformed the additional growth from the mono- to the dihydrate form of calcium oxalate.