Is Premarin Advisable For HRT Treatment?

i ran out of my estratest HS .625/1.25 and I won't be able to get my new script until tues/wed. the pharmacy had an old script for premarin .625 from years ago and filled it. is it safe to take this until my other meds are filled or is it better to wait and take nothing? this is for HRT total hysterectomy age 39 and I am 44 yrs old now. s