NIFEDIPINE FIRST GENERIC APPROVAL GRANTED TO PUREPAC; EFFECTIVE DATE

NIFEDIPINE FIRST GENERIC APPROVAL GRANTED TO PUREPAC; EFFECTIVE DATE of the ANDA approval, however, is delayed until an as-yet-undetermined date because of ANDA exclusivity that may be granted to another company. Purepac received approval for nifedipine 10 and 20 mg caps (Pfizer's Procardia and Miles' Adalat) on April 28. Under provisions of the Waxman/Hatch law, the first company to submit an ANDA for a generic drug and successfully challenge the innovator's patent is entitled to 180 days of marketing exclusivity, starting from either the date of its approval or the date of a court ruling of noninfringement. FDA explained in its approval letter to Purepac that an undisclosed generic firm submitted its nifedipine marketing application prior to Purepac and is currently in litigation with Pfizer over the validity of the nifedipine patent, which expires in January 1991. "Because of this litigation, the effective date of approval of your application must be delayed until a ruling by a court that the patent is invalid or will not be infringed, or the drug product which is the subject of this previously submitted application is the first commercially marketed, whichever is earlier," FDA told the generic company. The patent reportedly covers formulation of the drug. Purepac is also still in litigation with Pfizer over the nifedipine patent. Purepac's approval marks the second time that a generic firm has been delayed from entering the market by ANDA exclusivity provisions when the exclusivity holder had not yet received its ANDA approval. American Therapeutics received the first approval for a generic version of Lederle's Maxzide in November 1987, but was prevented from marketing because of an exclusivity grant to Vitarine. Vitarine subsequently received ANDA approval in December, starting off the 180-day exclusivity time clock.