We researched this when our 10 yr old was prescribed Stilbestrol and couldn't find anything. She started on a daily dose for a week and then we were able to wean her off to a dose every 2-3 days. Worked like a charm until she passed at 15 yrs.
Diethylstilbestrol (DES) is primarily used in the treatment of sphincter tone incontinence in female dogs. DES is used at extremely low doses thus avoiding any toxicity issues that have been a problem for estrogen derivative medications.
If the incontinence is not controlled after one week of DES therapy, then DES will not be effective for your dog. If it is effective, you may need to treat once every 3-10 days to control the incontinence. Most dogs need to be treated long term, but some dogs may only need to be treated seasonally or for several months.
There is also another medication called Proin (Phenylpropanolamine) that can be used affectively for treatment of urinary incontinence. It is a non-estrogen medication for those who are concerned with using hormone therapy for incontinence issues. This particular medication can be used to treat males with urinary incontinence problems where you obviously can not use Estrogen.....Best of luck.