Toxicology Testing in Death

Drugs cause or contribute to a huge number of deaths. (When I talk about drugs I include alcohol, our most misused and most dangerous drug. Alcohol is a drug, it is actually a narcotic.) Those deaths include the obvious accidental and non-accidental overdose or over-use, as well as a large drug contribution to motor vehicle-related deaths of passengers, drivers, and pedestrians. Drugs (both licit and illicit) often contribute to other pathology-related deaths, e.g. a guy with sleep apnea takes a sleeping pill too many or one drink too many and he wakes up dead in the morning. Drug-drug interactions are often deadlier than a single drug alone. For example, mixing a benzodiazapine (like Xanax) with alcohol or other narcotics can be deadly. Drugs (especially alcohol) also tend to increase our level of stupidity, allowing us to try things that we wouldn’t try sober (Can I get this car up to 100 mph?). And drugs make it more difficult to protect ourselves by means of reactions we rely on so much.

Medicolegal death investigators do toxicology testing in almost every case, checking various body fluids for the presence of drugs of all sorts. You never really know if the drugs are there or not if you don’t test. I have seen cocaine in an 80 year old woman that you wouldn’t have suspected looking at her, she looked just like my grandmother. Those samples are usually sent out to be tested. There a only an handful of “reference labs” in the country that will do drug testing on decedents’ samples and on certain body fluids that we often do testing on. Sending out the samples is why you always hear that “tox is pending” with results expected in 3-4 weeks.

I use the term body fluids a bit loosely, because sometimes we even test pureed liver. We test a variety of body fluids routinely. Blood is the most frequently tested. While it can give very important results, it does have some limitations. Finding drugs (including alcohol) in the blood is the most frequently used proof of impairment by a substance, depending on the level present. Continued breakdown of drugs in the blood and/or their spreading out of the blood stream to other body compartments after death (redistribution) can artificially lower levels present at the time of death. Finding cocaine, itself, in the blood reflects use within a few hours of death. However, it also continues to be broken down in the blood stream by enzymes in our blood cells. That breakdown can also occur after the samples are drawn if they are not refrigerated. Therefore cocaine test levels may not accurately predict what was present at death. Delta-9-THC in the blood reflects use within about an hour of death, while Carboxy-THC can be found in the urine for a time up to a week after use. Presence of THC in the urine does not indicate impairment, only use. Vitreous, the gel/fluid center of an eyeball, is an excellent testing fluid because it is often the best reflector of the drugs that were bathing the brain at death. We can also test bile, but it can only tell us that use was sometime within the last 2-3 weeks.

In my next post I will dissect some real toxicology numbers to show you how we sort through those numbers in making our decisions.

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