Report No: DOT/FAA/AM-00/29

Title and Subtitle: Distribution of butalbital in biological fluids and tissues

Report Date: August 2000

Authors: Lewis, R.J., Southern, T.L., Cardona, P.S., Canfield, D.V., and Garber, M.

Abstract: During the investigation of fatal aviation accidents, postmortem samples from the pilot/copilot are submitted to the Federal Aviation Administration's (FAA's) Civil Aerospace Medical Institute for toxicological analysis. Blood specimens are received in approximately 70% of the fatal aviation accidents analyzed by the FAA's Toxicology and Accident Research Laboratory. The lack of blood available is usually due to the severe damage to a pilot's body during an aviation accident and/or to the length of time taken to recover the body following an accident. Therapeutic and toxic levels for most drugs are reported in the scientific literature for blood and plasma only. Therefore, it is imperative for an accident investigator and forensic toxicologist to be able to estimate drug concentrations in a fatal aviation accident victim's blood from the available concentrations in the tissue.

This is exemplified by a recent aviation fatality where butalbital was identified in muscle tissue of a pilot, and the investigators wanted to know the approximate butalbital concentration expected in the victim's blood. Butalbital, a short-acting barbiturate found in combination with other drugs such as acetaminophen, aspirin, codeine, and caffeine, is commonly prescribed for the treatment of tension headaches. Certain side effects of butalbital, such as drowsiness, sedation, dizziness, and a feeling of intoxication, could affect pilot performance and become a significant factor in an aviation accident.

Thus, our laboratory determined the distribution of butalbital in various postmortem tissues and fluids. The distribution coefficients established for butalbital, expressed as specimen/blood ratios, were found to be as follows: muscle (0.66 ± 0.09), kidney (0.98 ± 0.09), lung (0.87 ± 0.06), spleen (0.75, ± 0.03), brain (0.96 ± 0.07), liver (2.22 ± 0.04), liver fluid (0.89 ± 0.23), heart (0.91 ± 0.17), bile (0.94 ± 0.22), and urine (0.73 ± 0.16). The results demonstrate that muscle, kidney, lung, spleen, brain, liver, and heart can be used reliably to estimate butalbital blood concentrations.

Key Words: Forensic Science, Toxicology, Butalbital, Distribution, Sedative, Postmortem Drug Analysis, Aircraft Accident Investigation

No. of Pages: 7