Is It Safe To Retake Meprate If My Period Hasn’t Started Yet?

I had missed my period and it was 35th day usually I used to get my period by 30th day as we had some Pooja I consulted a gynaecologist and she suggested me to take pregnancy test which was negative and again confirmed with Bhcg which was negative there also and she prescribed me to take meprate 10mg twice a day for 3 days. And she told me that I will get my period in the next 3 days but it’s already 5 days now still haven’t got my period. So she has told me to wait for one more day and start taking the tablet again if I don’t get my period till I want to postpone it . Is it okay to take tablet again