Act Nvp Tablet is a combination of two medicines: Doxylamine and vitamin B6 (pyridoxine) which treat nausea and vomiting associated with pregnancy. Doxylamine is an antihistamine which works by blocking the action of a chemical messenger (histamine), thereby controlling nausea, vomiting, and dizziness. Pyridoxine (vitamin B6) is a form of vitamin B which possesses anti-nausea properties.