Phenobarbital Used Primarily as a Sedative

Phenobarbital, the barbiturate found in the bloodstream and possessions of USAir Capt. Colin F. Shaw after his 737 crushed a SkyWest commuter plane at Los Angeles International Airport on Feb. 1, is a central nervous system depressant whose primary use is as a sedative.

In lower doses, it is used as an anticonvulsant to block epileptic and other types of seizures.

Phenobarbital is also an ingredient of some combination drugs, such as Donnatal, which is designed to relieve gastrointestinal distress. It relaxes the colon, alleviating spasms.

Shaw’s physicians prescribed the drug over a period of years to relieve “gastrointestinal distress” and “spastic colon” caused by anxiety, according to the National Transportation Safety Board. It is not clear from the board’s report whether Shaw received a drug like Donnatal or pure phenobarbital.

But the latter “would be an unusual choice for a gastrointestinal disorder,” said USC pharmacologist Michael Wincor.

Phenobarbital is addictive, and its effects are magnified by simultaneous use of alcohol.

The drug’s major side effects are drowsiness and slowed reaction time. According to the National Transportation Safety Board, Shaw normally drank four or five cans of beer per day.

But pharmacologists contacted by The Times indicated that the amount of phenobarbital found in Shaw’s body after the crash was so low that it probably had no effect on his performance in flying the airplane.

Neuropharmacologist Stanley Cohen of Georgetown University in Washington said that Shaw’s blood contained “a very, very tiny dose . . . less than 1/15th of the minimum therapeutic level for treating epilepsy.” Cohen, who is acting as a consultant to lawyers involved in lawsuits resulting from the crash, argued that “the amounts of the drug in (Shaw’s) brain and blood were far too low to produce any impairment.”

Furthermore, Shaw’s long history of phenobarbital use--15 years of at least intermittent use--would probably render him tolerant of its effects. “One could argue that someone who is chronically taking phenobarbital and chronically drinking five cans of beer per day develops a tolerance and could conceivably walk around as well as you and I,” Wincor said.

But, he added, “any time you are working with someone like a pilot or a fireman or someone who has to be alert, you think twice about using a central nervous system depressant” like phenobarbital. “You may have no alternative, but it’s something you think about.”