In early January Brenton “Brent” Saunders, the chief executive of upstart pharmaceutical giant Actavis , reclined in a medical chair on a stage in an Orlando hotel ballroom as a plastic surgeon pierced his face 30 times, delivering needles full of Botox to the crooks of his eyes and nose and injecting Juvederm Voluma, a dermal filler, into his cheeks. A cameraman documented every prick and projected it on a huge screen behind him. These are bestselling products for Allergan AGN -0.51%, which Actavis is buying for $67 billion, the biggest health care deal in six years. The audience, 1,000 Allergan sales reps, went wild.