Oxycodone Overdoses
Recently I was asked to review a very sad and heart wrenching potential medical malpractice case. A young man died following the administration of Oxycodone.
The family was upset stating it was a physician error and negligence in prescribing. The medical coroner was calling it an overdose. The family was very upset at the implication that it was an intentional, suicidal overdose.
After careful review of the medical and pharmacy records we did determine that the dosing and directions for use of the Oxycodone was reasonable. The question then became was it an accidental overdose vs an intentional (suicidal) gesture on his part.
In looking the pharmacology of this medication there were several important areas we had to highlight for the attorney requesting the review.
The first was looking at the onset of action and duration of action. Following an oral administration of immediate release oxycodone the onset of action is about 30-45 minutes with the duration of action of about 4 hours.
Next was looking at the half life of oxycodone, which is about 4-6 hrs. This means that after 4-6 hrs half of the drug remains in his/her system and may take another 4-6 hrs to remove half of the half that is remaining. This is very important especially when a patient is using multiple doses throughout the day. The potential exists for a cumulative build-up, even though patients may not be continuing to feel the analgesic effects.
When reviewing post-mortem lab analysis of drug levels it is important to first identify how soon after death the samples were taken. Following death, drugs undergo a re-distribution into blood from solid organs such as the lungs, liver, and myocardium. This is known as postmortem redistribution (PMR). This is important to understand because it may not reflect what was in the person’s blood stream at the time of death!!
Pharmacological principles including drug properties such as volume of distribution, lipophilicity, and pKa are important factors when considering PMR. For example basic, highly lipophilic drugs with a volume of distribution greater than 3 l/kg are most likely to undergo PMR.
Oxycodone is a highly protein-bound drug (45%) with a large volume of distribution (Vd) which results in substantial distribution among all tissues and fluids in the body.1 Studies done by the FAA on PMR of oxycodone1 differentiate that therapeutic concentrations of oxycodone range from 0 .01 to 0.10 mg/L while toxic levels of oxycodone are reportedly in the 0.20-5.00 mg/ml range but may vary greatly .
Studies have been done which specifically address the differences of PMR oxycodone between suicide cases vs unintentional overdoses.2 In cases of suicide by oxycodone overdoses, the post mortem concentrations ranged from 0.6-8.0mg/L. In situations defined as “an unintentional–or ‘functional’ overdose the post mortem concentrations ranged from 0.16 to 0.93mg/L
In reviewing the autopsy report for this young man it was noted his PMR oxycodone level was 0.189mg/L consistent with data supporting an accidental or unintentional overdose.
Lastly, the question that needed to be answered was “where there any other factors which may have contributed to his demise as result of taking Oxycodone?”
And the answer was yes. He was a large, obese man (BMI 40%) with a history of sleep apnea that refused to use a CPAP. The respiratory suppressive effects of Oxycodone are well known, especially in patients with obstructive sleep apnea.
If you have a case you would like reviewed, please contact me directly.
References:
1. Botch, SR Distribution of Oxycodone in Postmortem Fluids and Tissues www.faa.gov/library/reports/medical/oamtechreports
http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA531004
2. http://library-resources.cqu.edu.au/JFS/PDF/vol_48/iss_2/JFS2002309_482.pdf