<s>[INST] Hello, I am a 42 year old female with high blood pressure and I just changed from atenenlol .25 to lisinopril 20 I have taken the new med as the pharmacy instructions indicated, upon waking on an empty stomach with 8 oz water. I am fine then when I lay down at night to go to sleep my heart starts pounding in my chest. I called my dr as I m on vacation and lo and behold so is he but the office told me to take it at bedtime instead. I am very nervous to do this, does this seem like the correct solution and since I m so anxious would it be ok to take a xanax (1/2 of a .25) to take the edge off? YYYY@YYYY [/INST] There is no problem if you take lisinopril at night, rather there are some isolated papers which say that the risk of MI air stroke is maximum in early morning, where your Blood pressure is found to be high, so night dose would be a better alternative.  So by all means take it at night.  Also taking Xanax would be ok.  Lastly for reassurance, atenolol apart from decreasing your blood pressure also decrease your heart rate, when you suddenly change sometime your baseline heart rate increases, and you may feel palpation.  It goes off in a week or too.  Have a good day.  Regards </s>