Thank you for asking on HCM. I really understand your concern and I m trying my best to help you. Most common side effects of Flomax (Tamsulosin) are: - abnormal ejaculation - back pain & body aches - lack or loss of strength - dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position, etc Some of the side effects that can occur with tamsulosin may not need medical attention. As your body adjusts to the medicine during treatment these side effects may go away. Some rare side effects of Flomax that needs medical attention: - chest pain - painful or prolonged erection of the penis - feeling of constant movement of self or surroundings etc. Kindly rate my answer as helpful. Dr. Elton