How often do taste buds change? an allergy pill i use to take didn't have really a taste last month now it taste really bad

Not possible: Taste buds do not change.

Sense of taste: Lots of things can effect taste. Here's an interesting article to read: http://www.popsci.com/article/science/7-things-affecting-your-sense-taste Was the medication from the same bottle? It might have even been the same generic medication tabs from different manufacturers in the same bottle.