# PharmPK Discussion - Arishel Newsletter, Issue 2, 2007: DUI PK

PharmPK Discussion List Archive Index page
• On 16 Sep 2007 at 02:50:57, Clerk Maxwell (clerkmaxwell.at.hotmail.com) sent the message
`Driving Under the Influence of Alcohol (DUI): PK Legal AspectsConsider the following example.  You are a 140 pound healthy male whois attending a party.  You start drinking beer at 10 P.M. andcontinue for about 30 minutes.  You leave the party to drive home at11:00 P.M.  You are stopped by a police officer at 11:30 P.M, whotakes you to a police station for suspicion of DUI.  At 2:00 A.M.,you breath into a machine that measures your breath alcohol (via IRspectroscopy), and a proprietary (unknown) algorithm converts yourbreath alcohol concentration to blood alcohol concentration (BAC).Your blood alcohol value turns out to be 0.06 grams per deciliter.This is below the DUI threshold of 0.08 grams per deciliter.  But thequestion is this: what was your blood alcohol concentration at 11:30P.M., when you were stopped driving by the police officer.  In somejurisdictions, a so-call "retrograde extrapolation" calculation isutilized, employing the Widmark equation.  In its pristine form, theWidmark equation is:C(t)  =  C(0)  -  K(t)where t = time, C(t) is BAC at time t, C(0) is BAC at time zero, K isthe zero-order, fractional hourly decrease in BAC ("burn-off rate,"with units of 0.017 grams per deciliter).But in this case, the question is what was your BAC at the time thepolice officer stopped you at 11:30 P.M., viz, 2.5 hours prior toyour BAC testing.  Employing "retrograde extrapolation," the Widmarkequation is re-arranged as follows:C(11:30 P.M.)  =  C(2 A.M.)  +  (0.170)(2.5 hours)  =C(11:30 A.M.)  =  0.060 +  (0.017)(2.5 hours)  =  0.125, over thethreshold of 0.08.  So, you are arrested, finger-printed, and sent tojail.Keep in mind, this could happen to you.A good DUI attorney and consultant could find at least 20 ways toattack the DUI arrest.  From a PK standpoint, where would you findall the potential errors (rhetorical question)?Have yourself a "field-day," especially Nick Holford who haspublished on BAC PK.Harold Boxenbaum, Ph.D.Pharmacokinetic ConsultantArishel Inc.14621 Settlers Landing WayNorth Potomac, MD 20878-4305(P) 301-424-2806(C) 240-422-0525(F) 301-424-8563Email: harold.at.arishel.comWebsite: www.arishel.com`
Back to the Top

 Want to post a follow-up message on this topic? If this link does not work with your browser send a follow-up message to PharmPK@boomer.org with "Arishel Newsletter, Issue 2, 2007: DUI PK" as the subject Support PharmPK by using thelink to buy books etc.from Amazon.com

Copyright 1995-2011 David W. A. Bourne (david@boomer.org)