Is it safe to use lisinopril instead of hctz?

My friend gave me some pills and said they are lisinopril.  See my other post at http://www.pharmer.org/forum/discussion-prescription-and-otc-meds/rx-over-534-lisinopril

If they are lisinopril, is it safe to substitute these for the 25 mg hctz I take?

I'm not looking for medical advice but want to make sure I don't die or something bad happens.  My doctor is out of the office for two weeks.

My hypertension is mild so changing medicine for a couple of weeks shouldn't be too big of a deal.  I've been on the hctz for about 3 weeks and find I'm constantly getting up during the night to visit the bathroom.  Then I can't go back to sleep.  So I want to try something else and see if it will improve my sleep patterns.

Thank you very much.