Before dental work is septocaine safe as well as clindamycin?

Yes. Clinda can cause upset stomach, so watch for that. Septocaine is fda approved, & quite safe & strong, when used intelligently.
Yes. Septocaine is an anesthetic and Clindamycin is an antibiotic. Both are very safe, but as with all drugs there are precautions. Your dentist will advise you about these drugs.