Is it okay to take berberine and valacyclovir in the same day? how do the two interact together?

Should be safe: In general, vitamins, supplments, and such products -- like berberine -- do not interact in important ways with any prescription drugs. I doubt the combination of berberine and valcyclovir has been studied, but I wouldn't worry about it. FYI, if you google "drug interactions", you'll find many website on which you can enter almost any drug names to see if there are interactions.