You might call Tim Barberich the Mr. Fixit of the drug industry.

Barberich is the founder of Sepracor Inc., a small high-tech research firm with a unique goal: to fix what's wrong with some of medicine's best-known drugs by chemically extracting their harmful side effects."We use pharmacology to find out what's causing the side effects and how to eliminate them," said Barberich, a 47-year-old chemist.

Glamorous work it isn't. Most researchers would probably rather be searching for the cure for cancer or AIDS.

But, if Barberich's hopes pan out, in a few years Sepracor will have a stable of blockbuster medications to rival those from the world's pharmaceutical leaders. He will transform his obscure company into the undisputed leader of a new niche industry.

And patients will have a little more peace of mind knowing the pills they're taking won't do them more harm than good.

Consider these possibilities:

- A powerful over-the-counter version of a prescription painkiller called Orudis that doesn't upset your stomach like aspirin or Advil, and doesn't cause liver damage that some doctors blame on Ty-len-ol.

- A new version of the popular allergy drug Seldane that dries your sinuses without putting you to sleep and doesn't interact with other drugs to cause potentially fatal heart arrhythmia.

- An asthma inhaler with the generic drug albuterol that stops attacks, but is free of molecules believed to cause "hyper-reac-tiv-ity," a condition that makes asthma attacks more frequent, intense and potentially deadly.

For now, Sepracor's hopes for these drugs and others remain in its laboratories.

In the company's 10-year existence, it hasn't earned a profit. Its first medicine is at least two years away from your corner pharmacy.

As a result, Wall Street has largely ignored the company, bundling it with hundreds of fledgling biotechnology firms whose drug prospects are iffy at best.

However, stock analysts who've looked closer are telling their clients to buy Sepracor. Sepracor's drugs have have already been proven effective and safe for most people, they argue. All it's doing is making them safer.

"Their strategy is smart," said David Steinberg, with Volpy, Welty & Co. in San Francisco.

The key to Barberich's plan is a chemical concept called chirality, a characteristic shared by the vast majority of today's drugs.

Chiral chemicals consist of two molecules known as isomers which share the same chemical structure, but in a mirror image - just like left and right hands. The name chiral is derived from the Greek word kheir, for hands.

Often only one isomer is responsible for a drug's desired results. The other may be inert, or it can interact elsewhere in the body with disastrous effects.

The best known example is Thalidomide, a drug given to pregnant women in the 1950s. One isomer cured morning sickness. The other caused severe birth defects.

Serious side effects often fail to turn up until after a drug is already on the market, being taken by millions. But, Barberich says no drugmaker wants to pull its drugs back into the lab to fix them for fear of inadvertently discovering still newer side effects.

"They'd rather work on a new compound that was better than the first one."

Barberich founded Sepracor as a business that separates chemical components and purifies chemicals for use by other drug companies. He soon figured out he could use these technologies to extract the bad isomers, or other molecules, and repair these drugs for a fraction of the cost and time it takes to develop new ones.