Updated from 2:30 p.m. EDTShares of aaiPharma ( AAII) were among the worst-performing health and pharmaceutical stocks Friday, falling 18.1% after the company said it would not be able to make its $10 million interest payment scheduled for today. Lenders have granted the drugmaker a 30-day grace period, but if the company fails to make the payment by Oct. 31 it will be in default. The company said there is a likelihood that it will be in default of certain covenants under its senior credit facility; the company is seeking waivers and consents for these defaults. Shares traded down 28 cents to $1.27. Cyberonics ( CYBX) fell 7.9% after Advanced Neuromodulation Systems ( ANSI) dropped its $22-a-share offer for the company. "We are disappointed that the Cyberonics board of directors has chosen to reject our invitation to discuss a business combination," ANSI said. ANSI, which owns about 14.7% of Cyberonics, will continue to manage its investment as a shareholder, saying "we genuinely wish Cyberonics the best as it works toward fulfilling its mission." Shares of Cyberonics traded down $1.61 to $18.85. Shares of ANSI traded up 52 cents to $30.87. Shares of Nastech Pharmaceutical ( NSTK) fell 8.3% after the company filed an $80 million shelf registration statement with the Securities and Exchange Commission. The pharmaceutical company said that proceeds from any future products would be used for general corporate purposes. Shares traded down $1.18 to $13.11. eResearchTechnology ( ERES) fell 2.8% after it lowered its third-quarter financial outlook and warned that results would miss expectations. The company now expects earnings of 13 cents to 14 cents a share on sales of $27 million to $28 million. Previously, it forecast earnings of 16 cents to 17 cents a share on sales of $30 million to $30.5 million. Analysts polled by Thomson First Call had expected earnings of 16 cents a share on sales of $30.7 million. Third-quarter results were hurt by delays in phase I studies, the company said. Looking ahead, eResearch now expects full-year earnings 58 cents to 60 cents a share on sales of $112 million to $115 million. Previously, it forecast earnings of 62 cents to 63 cents a share on sales of $117 million to $119 million. Analysts had expected earnings of 61 cents a share on sales of $118.8 million. Shares traded down 37 cents to $12.96.