Shares of Durect (NASDAQ: DRRX), a Cupertino-based developer of drug-delivery technologies, fell 30 percent in morning trading to $2.21 after the FDA handed a complete-response letter to licensing partner Pfizer (NYSE: PFE) on an extended-release version of the pain drug oxycodone. The product, called Remoxy, is being developed by New York-based Pfizer and Pain Therapeutics (NASDAQ: PTIE) of Austin, and it includes anti-tampering technology licensed from Durect. The project has suffered some regulatory hurdles, including a previous complete-response letter issued in December 2008. Pfizer said in a statement that it would work with the FDA to address the issues raised in the current letter. Shares of the New York-based drug giant dipped about 1 percent to $20.28.