WASHINGTON (AP) _ Bristol-Myers Co. will begin marketing in early December a new tranquilizer that treats anxiety disorders without causing drowsiness or impairing a person's ability to drive or work, the company said Wednesday.

The Food and Drug Administration approved the drug, buspirone hydrochloride, which will be marketed by Bristol-Myers' Mead Johnson Pharmaceutical Division under the name BuSpar.

The drug, which will be available by prescription, differs from the current class of commonly used tranquilizers, including Valium, which can interfere with normal performance, FDA spokesman Brad Stone said.

''It has very limited side effects as far as causing drowsiness or reducing functional ability,'' Stone said. ''It won't affect your ability to perform everyday tasks like driving or operating heavy machinery.''

Clinical trials found no evidence that buspirone hydrochloride causes physical dependency, Stone said.

Bristol-Myers said the drug, when mixed with alcohol, appears to cause none of the adverse reactions that can occur with other drugs, providing an ''additional margin of safety for patients.''

Additionally, ''BuSpar dues not cause the euphoric or sedative effects which can often lead to abuse ... (and) is unlikely to be utilized by illicit drug users,'' the company said.

Minor side effects caused by the drug can include upset stomach, diarrhea, dizziness and headaches, said company spokesman Scott Litherland.

Stone noted that, unlike Valium and other benzodiazepines, BuSpar is not useful as a muscle relaxant or anti-convulsive agent. He also said the drug initially is not as effective in patients previously treated with benzodiazepines.

Bristol-Myers developed the drug in 1967 and has conducted clinical trials with patients since 1978, Litherland said.

The unique characteristic of BuSpar is that, unlike benzodiazepines, it does not depress the entire central nervous system. While its ''exact mechanism of action is not totally understood,'' the drug is believed to act directly on brain receptors responsible for anxiety, Litherland said.

The American Psychiatric Association estimates that more than 13 million Americans suffer from general anxiety disorders, which are characterized by persistent physical tension, hyperactivity in certain bodily functions, pervasive feelings of apprehension and emotional agitation, Stone said.