I stumbled across this remedy on a forum recently. I had remembered I used to take magnesium regularly due to migraine headaches and other problems (magnesium is a very important nutrient that many are deficient in). Jogging my memory, I remembered that on occasions when I could last as long as I wanted (and even sometimes too long) was when I had taken magnesium shortly before while more often than not I would suffer extremely premature ejaculation. I would recommend taking 400mg daily and then another 400mg 30 minutes to an hour before sexual activity. You should experiment with what dosage and frequency is right for you. If you start getting loose stools than you are likely taking too much. I have found Magnesium Citrate works very well. Some of the other ones like Magnesium oxide are not as well absorbed.