Prep for #cclivechat March 30, 2012 with Peter Mullen

sum it upWe have a very special #cclivechat this coming Friday. Peter Mullen will be our guest. Peter will discuss postmortem toxicology and pharmacokinetics with us.

Peter was a tenured member of the Department of Pharmacology at the University of Manchester prior to establishing Kemic Bio-research. He wrote down a few introductory statements to set the scene for his session on “pharmacokinetics and postmortem toxicology” on #cclivechat, March 30, 2012.

Pharmacokinetics (toxicokinetics) is that branch of pharmacology (toxicology) focused on describing the disposition of a xenobiotic (a drug or any other chemical foreign to the body) in the body over time. In sequence, the main dispositional processes are: absorption into, distribution within and elimination from, the body. Since it utilizes mathematical equations to describe (model) these kinetic processes, pharmacokinetics is perceived as being (and can be!) a rather complicated discipline. Simply stated, however, pharmacokinetics is concerned with understanding the “time-course” of a substance in the body. Some basic pharmacokinetic descriptors include: elimination half-life, clearance and volume of distribution.

If a blood (plasma) concentration measurement of a drug is known, pharmacokinetic modeling may be used to provide extrapolative estimates of its concentration at key earlier or future times and possibly even a rough estimate of the dose administered. {Note: Estimates of the amount (dose) taken and the time of its occurrence cannot be done reliably based on a concentration measurement of the substance in a single urine specimen.}

It should be emphasized that the extrapolative utility of pharmacokinetics is limited mostly to the living. Postmortem toxicological applications of pharmacokinetics to estimate antemortem concentrations and amounts are fraught with many possible problems of interpretation due to such phenomena as postmortem redistribution of the substance within the cadaver. The concentration of a xenobiotic in postmortem blood may vary depending on the sampling site, time since death, the physical-chemical nature of the xenobiotic itself, presence (or lack) of preservative in the sampling container, etc. Accordingly, concentration measurements in the vitreous humor of the eye (a relatively “protected site”) may also be undertaken to facilitate a better understanding of possible antemortem “levels” of the substance (especially alcohol).

See you Friday March 30, noon-1pm EST for #cclivechat!