In a small study (N=24) of two weeks duration in healthy men, dutasteride (0.5 mg daily) had no effect on how the body processes tamsulosin or terazosin.
These medicines are often taken together with some care. Your doctor may change a dose, space them apart or check on you more often. Make sure your doctor and pharmacist know you take both.
What to do: No effect was seen in a small study, so these are usually fine together. Still tell your doctor or pharmacist about all your medicines.