Petogen is a synthetic progestin. In the normal menstrual cycle estrogen makes the womb lining thicken and grow. Progesterone makes it mature and shed. If enough progesterone or synthetic progestin is given over a long enough period of time many patients have no bleeding at all. If that is not your objective then this may not be your best choice. Hopefully your daughter will become more regular as she matures. If not you may wish to try some type of oral contraceptive pill with a short three or four day placebo break. It may take several tries to find the the best method to help your daughter each method requires a few months for the body to get used to it. You should talk frankly with your daughter and let her participate in the decision. There is no harm in not having a period as long as it is secondary to the progestin.