Prevalence of chlorpheniramine in aviation accident pilot fatalities, 1991-1996

Chlorpheniramine is known to cause drowsiness, and this side effect has a potential to impair performance and could be a factor in accidents.

Therefore, to establish the prevalence of this drug in pilot fatalities of aviation accidents, a postmortem toxicology database--maintained at the Civil Aeromedical Institute--was examined for the presence of chlorpheniramine in the fatalities, occurred during 1991-1996.

There were 47 (2.2%) accidents involving chlorpheniramine. Of these, 16 had only chlorpheniramine at 109 ng.ml-1 (n = 4) in blood and 1412 ng.g-1 (n = 12) in liver. Other drugs were also present in the remaining 31 cases, wherein chlorpheniramine concentrations were 93 ng.ml-1 (n = 18) in blood and 747 ng.g-1 (n = 12) in liver. Ninety-five percent of all quantitated blood values were at or above the therapeutic level (10 ng.ml-1), giving a 100 ng.ml-1 (n = 21) mean blood value. The drug's mean liver concentration from all cases was 1080 ng.g-1 (n = 24). The average blood value was approximately 10 times higher than the therapeutic value.

The presence of other drugs did not appear to significantly alter the blood chlorpheniramine level, but no such correlation could be established with the hepatic value. The approximate 10-fold increase in the liver concentration was consistent with the general trend of drug distribution in the hepatic compartment. However, the contribution of postmortem redistribution of the drug to alter its concentration cannot be entirely ruled out. This study suggests that chlorpheniramine was present in some aviation fatalities at levels higher than therapeutic levels.