Sepracor Inc. said it has received notice of allowance from thePatent and Trademark Office on a patent that will cover use ofthe pure isomer form of nitrendipine, a drug for high bloodpressure that is now commonly prescribed as a mixture of twoisomers.

The patent is the first that will issue to the company to coveruse of the drug rather than its method of production.

Many drugs are sold as mixtures of two mirror-image isomers,of which only one is usually active. Such isomeric drugs aredifficult to separate chemically, and usually the inactive one isharmless. However, it can sometimes cause side effects, JamesW. Young, vice president and general manager, told BioWorld.

Sepracor said its form of the compound eliminates theundesired isomer. The company estimated the worldwidemarket for isomerically pure nitrendipine at $200 million.

Bayer AG of Germany markets nitrendipine, a calcium channelblocker, as an isomeric mixture.

Sepracor, based in Marlborough, Mass., specializes in separatingisomers into chemically and pharmaceutically pure compounds.It has filed for patents on the single isomer forms of 25 widelysold multiisomer drugs.

The company's stock (NASDAQ:SEPR) closed at $9, down 75cents. -- RF

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