When an ejaculating penis backfires, with the semen going into the bladder. Can be caused by diabetes, prostate problems, MS, spinal-cord injury, neurological wiring issues, or because a man clamps the end of his penis shut when he’s masturbating. Amoxapine, which is a tricyclic antidepressant that inhibits noradrenalin reuptake, is often used in the treatment for retrograde ejaculation in some countries. Pseudoephedrine, imipramine and buspirone are also effective for some men who suffer from retrograde ejaculation. Clamping shut the end of his penis before coming should only be done in the most dire of circumstances, unless a man wants to end up at the doctor’s office doubled over in pain and having to answer some really embarrassing questions.