Hi Karen,
PM works about as long as hops: the immediate estrogenic effects (bloating, headaches, foggy thinking) should start after about two hours, and last 5-8 hours. The deoxymiroestrol is probably digested to estradiol. Then the miroestrol is digested to deoxymiroestrol. You may experience a dip in the effect between 3 and 4 hours after taking PM.