BACKGROUND: Drug absorption within intestinal urinary diversions has been reported to cause prolonged and higher grade toxicity. OBJECTIVES: The aim of this study has been to determine the importance and significance of drug absorption via neobladder after ileocystoplasty. METHODS: Ten healthy adult mixed breed dogs of both sexes (7 males and 3 females), weighing between 15-25 kg were selected. The animals were randomly divided into equal test and control groups. In treatment group, partial cytectomy, resecting 50 percent of the bladder and immediate ileocystoplasty was performed by Lamesch and Dociu technique. In control group an ileal resection and intestinal tract re-anastomosis was achieved without partial cystectomy and ileocystoplasty. In all animals, blood and urine samples were taken before surgery, at hours 1, 3, 6 and 24 after oral administration of Furazolidone (100 mg/dog) and this process was repeated on days 7, 25 and 45 after operation at the same hours. After preparation of the samples, the Furazolidone was measured by HPLC assay. One way analysis of variance and Dunnet test were used for the analysis of the data and P values less than 0.05 were considered statistically significant. RESULTS: In test group, the blood samples showed significant changes of Furazolidone on day 25. The urine samples revealed significant changes on day 45 in both groups and on day 25 in test group. CONCLUSIONS: The results of this study showed absorptive effect of the ileum that decreases with time. Problems arising from drug reabsorption are usually rare and in most drugs a change in dosage (except those which have a narrow treatment ratio) may not be required.