Identification of cytochrome P450 3A1/2 as the major P450 isoform responsible for the metabolism of fentanyl by rat liver microsomes

Assisted suicide by fentanyl intoxication due to excessive transdermal application

Herein, we report a case of an assisted suicide committed by application of 34 matrix-based fentanyl-containing transdermal therapeutic systems (TTS) with different release rates. The TTS were supplied by the husband but administered by the deceased herself. Besides routine systematic toxicological analysis (STA), the concentrations of fentanyl and norfentanyl were determined in the blood (femoral and heart), urine, stomach content, brain, lung tissue, musculus iliopsoas, liver, kidney, bile and in some of the used TTS by LC-MS/MS. Blood levels of fentanyl were 60.6 μg/L in femoral blood and 94.1 μg/L in heart blood. These concentrations are in good concordance with levels described in cases with accidental or lethal suicidal fentanyl patch application. The organ distribution indicates an influence of post-mortem redistribution. The levels of residual fentanyl in the TTS were also determined. STA furthermore revealed supratherapeutic levels of bromazepam. Thus, the cause of death was a combination of fentanyl and bromazepam intoxication. However, considering the determined levels of fentanyl and norfentanyl in the entire set of specimens and the high toxicity in comparison to bromazepam, fentanyl was the leading toxic noxa.

Induction of CYP3A by ethanol in multiple in vitro and in vivo models

BACKGROUND

Cytochrome P-450 3A (CYP3A) is responsible for the metabolism of numerous therapeutic agents. The content of CYP3A seems to be affected by ethanol ingestion. Because ethanol is used widely, its potential interaction with CYP3A is of great interest. The effects of ethanol on CYP3A content and activity were assessed in different in vivo and in vitro models.

METHODS

Rats fed either the Lieber-DeCarli ethanol-containing diet or an ethanol and liquid diet via the intragastric tube feeding method were used. Additionally, HepG2 cell lines that constitutively and stably express human CYP3A4 were constructed to study ethanol interactions with CYP3A4.

RESULTS

In all models tested, ethanol induced CYP3A activity and content, as assessed by the metabolism of fentanyl, a sensitive and specific CYP3A substrate, and Western blot analysis, respectively. In the CYP3A4-expressing HepG2 cell line, incubation with ethanol caused a dose-dependent increase in CYP3A4 activity. Ethanol also increased messenger RNA levels of CYP3A4. In the HepG2-CYP3A4 line, incubation with cycloheximide caused a decrease in fentanyl metabolism secondary to a decrease in CYP3A4 levels; this decrease was prevented by coincubation of cycloheximide with ethanol.

CONCLUSIONS

Ethanol induced CYP3A activity and content both in vitro and in vivo. There may be multiple mechanisms of induction of CYP3A4 by ethanol, including stabilization of messenger RNA and protein. Ethanol-induced increases in both the protein level and activity of CYP3A4 may play a role that might be of pathophysiological or clinical significance.