Low Dose D-penicillamine in cystinuria.

(1) A single dose of D-penicillamine (not more than 750 mg) taken at 2200 h, together with a prescribed fluid intake of two to three litres during the waking hours, without extra drinks at night, is sufficient to keep the concentration of the urinary cystine below the saturating concentration of urine throughout the 24 h period. (2) This regime does not materially reduce the total 24 h excretion of cystine. (3) The effect of D-penicillamine is mainly seen in the urine excreted between 0200 and 0800 h. (4) This regime is provisionally recommended for the prevention of cystine stone recurrence but not for stone dissolution. Larger total amounts of D-penicillamine given in divided doses are still recommended for the latter purpose.