Shares of

BioCryst Pharmaceuticals

(BCRX) - Get Report

were among the best-performing health-related stocks Tuesday, jumping 18% after the Food and Drug Administration granted the drug developer's peramivir injection fast-track status.

Peramivir is an influenza inhibitor that has shown, in preclinical studies, activity against multiple strains of flu, including bird flu. The fast-track delegation, given to drugs that may fulfill an unmet need in treating life-threatening illnesses, allows for an accelerated approval process. In December, the FDA gave BioCryst the green light to begin human clinical trials using injectable peramivir. Shares were trading up $3.45 to $22.49.

Shares of

Guidant

( GDT) rose 7% after

Boston Scientific

(BSX) - Get Report

sweetened its offer for the company yet again. Boston Scientific is now willing to pay about $27 billion, or $80 a share, for the medical device maker, up from an offer Thursday of about $26 billion, or $73 a share. The new offer consists of $42 a share in cash and $38 a share in stock. The Boston Scientific offer is worth more than

Johnson & Johnson's

(JNJ) - Get Report

most recent offer of $24 billion, or $71 a share.

Boston Scientific said its amended offer will expire at 5 p.m. EST on Tuesday unless Guidant deems the offer superior to J&J's previous offer. In that case, Boston Scientific's offer will remain on the table until the close of business on Jan. 25. Shares of Guidant recently were up $5.23 to $76.07; shares of Boston Scientific fell $1.32 to $23.88; and Johnson & Johnson was down 60 cents to $61.22.

Forest Labs

(FRX)

fell 2% after the company posted third-quarter sales that fell short of expectations. The drugmaker reported earnings of $195.2 million, or 57 cents a share, on total sales of $757.8 million. The results included a royalty payment of 5 cents a share. Analysts polled by Thomson First Call expected earnings of 62 cents a share and sales of $762.1 million. During the year-ago period the company earned $260.8 million, or 70 cents a share, on sales of $832.3 million.

For 2006, Forest Labs forecast earnings of $2.30 a share, which excludes a one-time tax benefit of 10 cents a share. Analysts are projecting earnings of $2.31 a share. Shares were trading down 80 cents to $43.44.

United Natural Foods

(UNFI) - Get Report

traded actively after the distributor of natural and organic foods announced the resignation of its chief financial officer. Rick Puckett is leaving the company so that he can serve as financial chief at

Lance

(LNCE)

, a maker of snack foods. Puckett's resignation is effective Jan. 26. Controller Mark Shamber will serve as interim CFO while United Natural conducts a search for Puckett's replacement. Shares were trading up 12 cents to $28.03.

Other health care volume movers included

Pfizer

(PFE) - Get Report

, down 49 cents to $24.18;

Merck

(MRK) - Get Report

, down 15 cents to $33.32;

Elan

(ELN)

, up 49 cents to $16.51;

Bristol-Myers Squibb

(BMY) - Get Report

, down 13 cents to $22.29;

UnitedHealth Group

(UNH) - Get Report

, down 74 cents to $60.20;

Amgen

(AMGN) - Get Report

, up 41 cents to $78.01; and

Schering-Plough

( SGP), down 24 cents to $19.96.