Updated from 3:01 p.m. EDT

Shares of

Cyberonics

(CYBX)

were among the best-performing health and pharmaceutical stocks Friday after

Advanced Neuromodulation Systems

(ANSI)

took a 14.8% stake in the company.

Advanced Neuromodulation suggested it would consider a merger, but Cyberonics responded that it "is not interested in any combination or merger." Still, Cyberonics said ANS' purchase of nearly 15% of the company's shares is "evidence that yet another knowledgeable device market leader ... has recognized the value of Cyberonics' VNS Therapy franchise." Shares of Cyberonics traded up $4.63, or 31%, to $19.58.

Mylan Labs

(MYL) - Get Report

fell after it said that investors should not rely on published analysts' estimates for the company. Mylan said that

analysts' estimates do not appear to have "fully adjusted for negative changes in the generic pharmaceutical industry." As a result, Mylan suspended its 2005 earnings guidance and said that it would provide earnings guidance as soon as practically possible. Shares of Mylan Labs traded down 31 cents, or 1.8%, to $16.89.

Shares of

Pharmacyclics

(PCYC)

rose 8% Friday, a day after the company posted better-than-expected earnings results. The pharmaceutical company posted a fourth-quarter loss of 38 cents a share vs. a Thomson First Call estimate of a loss of 43 cents. A year ago, the company posted a loss of 46 cents a share. Shares of Pharmacyclics traded up 68 cents to $9.20.

Aetna

(AET)

rose after it agreed to purchase privately held Strategic Resource for $250 million in cash. Strategic Resource, a benefits management company that caters to part-time and hourly workers, provides services for more than 700 companies across 46 states. Aetna said it expects the transaction to close during the fourth quarter. Aetna also said the transaction would immediately be accretive to earnings. Shares of Aetna traded up $1.78, or 1.9%, to $94.23.

Other health care volume movers included

Genta

(GNTA)

, up 36 cents to $2.56;

Pfizer

(PFE) - Get Report

, up 26 cents to $31.74;

Schering-Plough

(SGP)

, up 40 cents to $18.63;

Amgen

(AMGN) - Get Report

, up 81 cents to $58.20; and

Boston Scientific

(BSX) - Get Report

, down 48 cents to $34.52.