Is it okay to take senna tea or a laxative while on antibiotics and vicodin?

Yes: Opiate-induced constipation is often better managed initially with a stool softener like colace (docusate sodium) or surfak, holding laxatives like senna for a second if twice daily stool softeners aren't effective. Antibiotics may produce diarrhea, so you need to be careful that you not use too much laxative, since the results may be (literally) explosive.