If you stop taking Flomax for several days in a row, call your doctor before starting the medication again. If you are allergic to Flomax or any of it's constituents you should not take Flomax without your doctor's prescription. Try to take Flomax pills at the same time each day. It is important to know that Flomax can cause dizziness, especially when you first stand up. The impact and the benefits of the medicine. Tamsulosin is an alpha-blocker drug used to treat an enlarged prostate. The same time each day. Try to take Flomax pills at the same time each day. Flomax can cause a drop in blood pressure upon first standing up, which in turn can lead to dizziness or fainting.