Hi, I'm taking Penicillin 500 prescribed by a Dentist, can I take 1 sedoxil? It is too late to call her, also she won't answer until Monday. Thank you

Yes. Yes, Should not be a problem. And you need a dentist who will respond across the weekend.
Yes. Antibiotics & anti-anxiety medications can be taken at the same time. Please know that your Pharmacist is a marvelous source of drug interaction knowledge. If you had both prescriptions filled at the same pharmacy the Pharmacist would have already checked for problematic drug interaction. Additionally, make sure you take the entire course of antibiotic, don't quit until all the pills are gone.