I am wondering if tulsi tea, made of indian basil, will affect any prescription or OTC drugs?

Yes. Tulsi can interact with blood thinners (coumadin/warfarin) or other meds that slow blood clotting (nsaids). Caution should thus be used if also taking garlic, gingko, omega-3 fish oils. Tulsi reportedly can interact with drugs used during surgery & cause bleeding complications. Definitely inform your docs if you are using this herb.