Cardura is a drug that relaxes the muscle fibers in the prostate and allows the urine to flow through more easily. It’s most troublesome side effect can be light-headedness due to lowering of the blood pressure. Detral relaxes the bladder muscle for patients who have an overactive bladder. The problem is that sometimes an overactive bladder can occur because of obstruction from an enlarged prostate. In this case, there is a risk of Detral relaxing the bladder to the extent that the patient might not be able to void.