If she brings on a period is she subject to the rulings thereon?
Question

                A woman brought on her period by using medicine, and she stopped praying. Should she make up the prayers or not?.
Praise be to Allah.
    A woman should not make up the prayers if she brings on her 
    period, because when the menstrual blood is present the rulings thereon 
    apply, just as if she takes medicine to prevent menstruation, then she has 
    to pray and fast, and she does not make up the fasts, because she is not 
    menstruating. The ruling is connected to the reason for it. Allaah says 
    (interpretation of the meaning): “They ask you concerning menstruation. 
    Say: that is an Adha (a harmful thing for a husband to have a sexual 
    intercourse with his wife while she is having her menses)” [al-Baqarah 
    2:222]. When that adha is present, the rulings thereon apply, and 
    when it is not present the rulings thereon do not apply. End quote. 

    Shaykh Muhammad ibn ‘Uthaymeen (may Allaah have mercy on 
    him).