My doctor put me on prilosec otc for 14 days. i take that in the morning before breakfast. can i take triphala (ayurvedic mix) too at night ?

Not enough data: Prilosec is a brand of omeprazole (http://www.drugs.com/omeprazole.html) which is a drug manufactured under auspices of FDA. As you noted, Triphala (http://en.wikipedia.org/wiki/Triphala) is an Ayurvedic formula, which like all over-the-counter herbs & dietary supplements, is manufactured w/o 3rd party quality control & oversight. I could not find any data linking these two, whether good or bad.