Pulse vitamin D3 (3-5 micrograms po, twice a week) has been proposed for individuals with hyperparathyroidism resistant to daily po vitamin D3 therapy. While pulse vitamin D3 is effective, concerns regarding oversuppression of parathyroid hormone (PTH) values leading to adynamic bone disease have arisen. In view of these concerns, minibolus vitamin D3 po therapy was utilized in dosages varying from 0.25-1.0 micrograms twice a week in an effort to control elevated PTH values in patients who failed standard daily vitamin D3 therapy. Eleven patients were changed to minibolus vitamin D3 therapy from standard daily treatment (6 women, 5 men; mean age 55.8 +/- 14 years), on continuous ambulatory peritoneal dialysis (CAPD) for an average of 28.4 +/- 23 months. The mean intact PTH (iPTH) values on 0.25 microgram/day decreased by 54.5 +/- 167.8 pg/mL compared to pretreatment values. The mean iPTH on minibolus vitamin D3 therapy decreased by 165.1 +/- 104 pg/mL. The response to minibolus vitamin D3 was not truly predicted by the baseline PTH values. While the average decrease in PTH was greatest on 1.0 microgram two times a week, 2 patients experienced a decrease greater than 200 pg/mL in PTH on a lower dose. The greatest effect on PTH with minipulse vitamin D3 occurred when iPTH was < or = 500 pg/mL. While total calcium increased on daily vitamin D3, there was no significant change with minipulse therapy.(ABSTRACT TRUNCATED AT 250 WORDS)