CAN SMALL COMPANIES FIND A way into a drug market dominated by giants -- without spending themselves broke on research and development?

Polymer chemistry may provide the opening. Used to make products as diverse as floppy disks and contact lenses, polymer chemistry is now becoming a passport to the drug industry. "This whole thing is moving at a very rapid pace now, and there are going to be some marketable things coming out shortly," says Guy Donaruma, provost of Polytechnic Institute of New York, in Brooklyn, and a pioneer in the field.

A polymer is a molecule in which a certain sequence of atoms is repeated over and over. Chemists can make a polymeric drug from scratch, or convert an existing drug into a polymer. Then, by altering the size or shape of the chain, they can fine-tune the way the drug acts in the body, creating a possibly new and improved version.

Polymeric drugs are a relatively fast and cheap route into the drug business. It costs about $94 million to bring a conventional drug to market. But companies can create new drugs from existing ones by combining them with polymers on making polymers of them, thereby slashing the cost of development. "We don't have to synthesize 100,000 compounds in order to find one that we can take to the clinic," says Carlos Samour, chairman of MacroChem Corp., of Woburn, Mass.

MacroChem is awaiting Food & Drug Administration approval of a drug it says would control epilepsy without a sedative effect. It has also filed a patent application for one that would help people sleep without inhibiting dreams. Both drugs would be improvements over barbiturates. Mission Pharmacal Co., a private San Antonio company, started marketing the first polymeric prescription drug -- a treatment for kidney stones -- in 1983.

Small companies won't corner polymerics for long. "You can bet that the big companies will jump on it," says Donaruma.