A new drug may one day make it possible for many people to both breathe comfortably and own a cat.

The drug, CI-949, is being tested at Fairfax Hospital for its ability to reduce the delayed symptoms of respiratory problems caused by CAT I, a protein found in high levels in cat dander, saliva, urine and feces.

Dr. Richard R. Rosenthal, chief of the allergy section at Fairfax Hospital and assistant professor at Johns Hopkins School of Medicine, says that cat dander is the most allergenic of all animal danders, affecting millions of Americans, and can induce symptoms such as runny or stuffy noses, itchy eyes, wheezing, chest tightness, shortness of breath and red and itchy skin.

These immediate reactions can usually be treated by staying away from cats or using antihistamines. The only immediate reaction treated with CI-949 would be chest tightness, and Rosenthal plans to test the drug's effectiveness in treating pulmonary reactions.

But some people, particularly those with asthma, also suffer tightening of the bronchial tubes, limiting air to the lungs up to 12 hours after exposure. This newly recognized delayed reaction is the main target of the new drug.

"People's attitudes toward cats are strange. Most cat owners will be willing to keep the cat and suffer," said Rosenthal. The more fastidious the cat, the more likely the exposure to CAT I, as cat saliva is very rich in this allergen.

Rosenthal and his staff began testing CI-949 last month. It causes the body to release a substance called slow-reacting substance of anaphylaxis, which relaxes the bronchi. If the tests are successful, the drug would be taken orally on a regular basis or as needed, depending upon the patient's illness.

In the ongoing study, patients shown to be sensitive to CAT I are exposed to small doses, after which their lung function is checked. Following a second exposure, some are given the drug, others a placebo, and lung function is checked again.

Volunteers for the study are as pampered as the cats they own, according to Rosenthal, who says patients are fed gourmet meals, housed in "tastefully furnished" single rooms, watch color televisions and are monitored carefully.

People interested in participating in the clinical trials may call 573-6500.

Cat owners shouldn't hold their breaths, though. Rosenthal doesn't expect to complete testing for a year, and if approved, the drug will not be available for several more years.