ANALYST: PRESCRIPTION ANALYSIS BRINGS MIXED NEWS

A Wall Street analysis tracking trends in prescription drugs shows strong growth for some of the industry's key product areas while revealing less-than-encouraging news for several individual companies.

In a recent market note, Albert Rauch, senior health care analyst at AG Edwards & Sons, writes that while total prescriptions for cholesterol medication are 11 percent higher than a year ago, Pfizer's Lipitor has slightly declined, perhaps due to "therapeutic substitution in front of generic Zocor." Bristol-Myers Squibb's Pravachol is down 36 percent, while Zetia has shown modest growth and Vytorin has increased 132 percent.

Another area on the rise is aromatase inhibitors, used to prevent breast cancer. Industry leader Arimidex, Femara and Aromasin were all up by at least 25 percent. Prescriptions for Eli Lilly's new diabetes drug Byetta increased by 55 percent in the last quarter alone.

Rauch writes that "news of 'sleep walking' risks seen with Ambien users may be causing weakness in the overall insomnia market." That drug, marketed by sanofi-aventis, as well as Lunesta and Sonata have all declined in the last quarter.