Death attributed to the toxic interaction of triazolam, amitriptyline and other psychotropic drugs

A case of fatal multidrug intoxication involving flualprazolam: distribution in body fluids and solid tissues

Purpose

Designer benzodiazepines (DBZDs) increasingly emerged on the novel psychoactive substance (NPS) market in the last few years. They are usually sold as readily available alternatives to prescription benzodiazepines (BZDs) or added to counterfeit medicines. BZDs are generally considered relatively safe drugs due to the low risk of serious acute adverse effects in mono-intoxication, though e.g., alprazolam seems to display an elevated risk of respiratory depression. Here we report on a fatal intoxication involving the novel DBZD flualprazolam.

Methods

A complete postmortem examination was performed. General unknown screenings and analysis of drugs of abuse were performed on postmortem samples by immunoassay, gas chromatography–mass spectrometry and liquid chromatography–mass spectrometry. The standard addition method was employed to quantify flualprazolam in postmortem blood and tissues. Finally, a toxicological significance score (TSS) was assigned.

Results

Flualprazolam was detected in heart serum (25.4 ng/mL) and peripheral blood (21.9 ng/mL) as well as in urine, stomach contents, brain, liver and kidney (65.2–323 ng/g). The cause of death was deemed as central nervous system (CNS) and respiratory depression with agonal aspiration of stomach contents, in the setting of a multiple drug intake. Given the concentration levels of the co-consumed CNS depressants, the contribution of flualprazolam to the death was considered likely (TSS of 3).

Conclusions

Our results support that highly potent DBZDs like flualprazolam carry an elevated risk for unintended toxicity, especially in association with other CNS depressants. A multidisciplinary evaluation of fatalities remains mandatory, especially when pharmacological/toxicological data on intoxicating compounds are lacking. To our knowledge this is the first report of flualprazolam concentrations in solid tissues in human.

Methods for the quantitative evaluation and prediction of CYP enzyme induction using human in vitro systems

IMPORTANCE OF THE FIELD

For successful drug development, it is important to investigate the potency of candidate drugs causing drug-drug interactions (DDI) during the early stages of development. The most common mechanisms of DDIs are the inhibition and induction of CYP enzymes. Therefore, it is important to develop co.mpounds with lower potencies for CYP enzyme induction.

AREAS COVERED IN THIS REVIEW

The aim of the present paper is to present an overview of the current knowledge of CYP induction mechanisms, particularly focusing on the transcriptional gene activation mediated by pregnane X receptor, aryl hydrocarbon receptor and constitutive androstane receptor. The adoptable options of in vitro assay methods for evaluating CYP induction are also summarized. Finally, we introduce a method for the quantitative prediction of CYP3A4 induction considering the turnover of CYP3A4 mRNA and protein in hepatocytes based on the data obtained from a reporter gene assay.

WHAT THE READER WILL GAIN

In order to predict in vivo CYP enzyme induction quantitatively based on in vitro information, an understanding of the physiological induction mechanisms and the features of each in vitro assay system is essential. We also present the estimation method of in vivo CYP induction potency of each compound based on the in vitro data which are routinely obtained but not necessarily utilized maximally in pharmaceutical companies.

TAKE HOME MESSAGE

It is desirable to select compounds with lower potencies for the inductive effect. For this purpose, an accurate prioritization procedure to evaluate the induction potency of each compound in a quantitative manner considering the pharmacologically effective concentration of each compound is necessary.

Bimodal targeting of microsomal cytochrome P450s to mitochondria: implications in drug metabolism and toxicity

IMPORTANCE OF THE FIELD

Microsomal CYPs are critical for drug metabolism and toxicity. Recent studies show that these CYPs are also present in the mitochondrial compartment of human and rodent tissues. Mitochondrial CYP1A1 and 2E1 show both overlapping and distinct metabolic activities compared to microsomal forms. Mitochondrial CYP2E1 also induces oxidative stress. The mechanisms of mitochondria targeting of CYPs and their role in drug metabolism and toxicity are important factors to consider while determining the drug dose and in drug development.

AREAS COVERED IN THIS REVIEW

This review highlights the mechanisms of bimodal targeting of CYP1A1, 2B1, 2E1 and 2D6 to mitochondria and microsomes. The review also discusses differences in structure and function of mitochondrial CYPs.

WHAT THE READERS WILL GAIN

A comprehensive review of the literature on drug metabolism in the mitochondrial compartment and their potential for inducing mitochondrial dysfunction.

TAKE HOME MESSAGE

Studies on the biochemistry, pharmacology and pharmacogenetic analysis of CYPs are mostly focused on the molecular forms associated with the microsomal membrane. However, the mitochondrial CYPs in some individuals can represent a substantial part of the tissue pool and contribute in a significant way to drug metabolism, clearance and toxicity.

How do azoles inhibit cytochrome P450 enzymes? A density functional study

To examine how azole inhibitors interact with the heme active site of the cytochrome P450 enzymes, we have performed a series of density functional theory studies on azole binding. These are the first density functional studies on azole interactions with a heme center and give fundamental insight into how azoles inhibit the catalytic function of P450 enzymes. Since azoles come in many varieties, we tested three typical azole motifs representing a broad range of azole and azole-type inhibitors: methylimidazolate, methyltriazolate, and pyridine. These structural motifs represent typical azoles, such as econazole, fluconazole, and metyrapone. The calculations show that azole binding is a stepwise mechanism whereby first the water molecule from the resting state of P450 is released from the sixth binding site of the heme to create a pentacoordinated active site followed by coordination of the azole nitrogen to the heme iron. This process leads to the breaking of a hydrogen bond between the resting state water molecule and the approaching inhibitor molecule. Although, formally, the water molecule is released in the first step of the reaction mechanism and a pentacoordinated heme is created, this does not lead to an observed spin state crossing. Thus, we show that release of a water molecule from the resting state of P450 enzymes to create a pentacoordinated heme will lead to a doublet to quartet spin state crossing at an Fe-OH(2) distance of approximately 3.0 A, while the azole substitution process takes place at shorter distances. Azoles bind heme with significantly stronger binding energies than a water molecule, so that these inhibitors block the catalytic cycle of the enzyme and prevent oxygen binding and the catalysis of substrate oxidation. Perturbations within the active site (e.g., a polarized environment) have little effect on the relative energies of azole binding. Studies with an extra hydrogen-bonded ethanol molecule in the model, mimicking the active site of the CYP121 P450, show that the resting state and azole binding structures are close in energy, which may lead to chemical equilibrium between the two structures, as indeed observed with recent protein structural studies that have demonstrated two distinct azole binding mechanisms to P450 heme.

Disputed case of homicide by smothering due to severe amitriptyline intoxication of the victim

We report a fatal case of a female for whom the forensic autopsy revealed injuries to the external respiratory orifices indicating smothering. Subsequent postmortem toxicological analysis confirmed heavy amitriptyline acute intoxication. The victim had serious psychological problems, was under long-term treatment with antidepressants and was a systematic alcohol abuser. Forensic autopsy determined damage to the external airways, along with multiple formal petechial hemorrhages (Tardieu) in various parts of the body. The presence of amitriptyline, nortriptyline and 10-hydroxynortriptyline was confirmed by GC-MS and quantified by HPLC in blood (7.0 microg/ml amitriptyline and 7.4 microg/ml nortriptyline). The cause of death was disputed between severe intoxication (poisoning or suicide attempt) and smothering due to controversial evidence.

Suicide by Multidrug Ingestion

A fatal suicidal ingestion of drugs, together with activated charcoal, is reported. The death occurred 31 hours after the self-administration. The autopsy revealed a large amount of gastric content that appeared to be a compact mass of black color. Toxicologic analyses showed the presence of toxic levels of desalkylflurazepam and trazodone; metamizole and pridinol were also detected. The obtained results supported the hypothesis of a death due to acute intoxication delayed by the self-administration of activated charcoal, which elimination was probably hindered by the action of pridinol.

Fatal blood and tissue concentrations of more than 200 drugs

Fatal drug concentrations in body fluids and tissue samples are presented for more than 200 drugs and chemicals of toxicologic interest. Additionally, a reference list is added with more than 600 original papers concerning intoxications with a lethal outcome. The data can be helpful for the interpretation and plausibility control in own cases of intoxication. However, they should be used with caution, because use of drug data without sufficient knowledge about the patient or victim, the circumstances of the case, and about toxicokinetics and toxicodynamics might give a wrong interpretation in a special case.

Toxicological interactions involving psychiatric drugs and alcohol: an update

This review focuses on the toxicological interactions between alcohol (ethanol) and psychiatric drugs (antidepressants and antipsychotics), including those leading to fatal poisoning. Acute or chronic ingestion of alcohol when combined with psychiatric drugs may lead to several clinically significant toxicological interactions. The metabolism of these drugs is generally but not always delayed by acute alcohol ingestion. Drugs undergoing metabolism may also show increased metabolic clearance with chronic alcohol ingestion. Therefore, the net effect may be influenced by internal (e.g. disease, age, gender), external (e.g. environment, diet) and pharmacokinetic (e.g. dose, timing of ingestion, gastrointestinal absorption, distribution and elimination) factors. Cases of fatal poisoning involving coadministration of psychiatric drugs, alcohol and other drugs prompted this review.

A case of fatal triazolam overdose

A 57-year-old man was found dead lying down in a bamboo thicket. Moderate to severe petechiae were present on his conjunctivae, buccal mucosa, and laryngeal mucosa at autopsy. Cardiac chambers contained a normal volume of fluid blood. Moderate atherosclerosis and fatty liver were observed. No remarkable changes, other than congestion in other organs, were observed. Gas chromatographic screening of the stomach contents, blood and urine was positive for triazolam and alpha-hydroxytriazolam that were confirmed by gas chromatography-mass spectrometry. Blood concentrations of triazolam and free alpha-hydroxytriazolam were 62-251 and 10-66 ng/ml, respectively. A substantial amount of triazolam was detected in bile (1130 ng/ml), but not in urine. Free and total alpha-hydroxytriazolam concentrations were 3920 and 7050 ng/ml, respectively, in the bile and 3710 and 9670 ng/ml, respectively, in urine. Organs contained 216-583 ng/g triazolam. The concentration of free alpha-hydroxytriazolam in the kidney (246 ng/g) was higher than in any other organ. Free alpha-hydroxytriazolam was not detected in the liver. The concentrations of total alpha-hydroxytriazolam in the liver and kidney were 784 and 381 ng/g, respectively. Free to total ratios of alpha-hydroxytriazolam were 0.14-0.56 in fluid samples and 0.56-0.92 in tissue samples, except for the liver. A large quantity of triazolam (8.4 mg) remained in the stomach. The victim probably died of postural asphyxia caused by triazolam poisoning.

Interindividual variability in inhibition and induction of cytochrome P450 enzymes

Drug interactions have always been a major concern in medicine for clinicians and patients. Inhibition and induction of cytochrome P450 (CYP) enzymes are probably the most common causes for documented drug interactions. Today, many pharmaceutical companies are predicting potential interactions of new drug candidates. Can in vivo drug interactions be predicted accurately from in vitro metabolic studies? Should the prediction be qualitative or quantitative? Although some scientists believe that quantitative prediction of drug interactions is possible, others are less optimistic and believe that quantitative prediction would be very difficult. There are many factors that contribute to our inability to quantitatively predict drug interactions. One of the major complicating factors is the large interindividual variability in response to enzyme inhibition and induction. This review examines the sources that are responsible for the interindividual variability in inhibition and induction of cytochrome P450 enzymes.

Determination of triazolam by GC-MS in two autopsy cases: distribution in body fluids and organs

A detailed procedure for analysis of triazolam by GC-MS was constructed in our laboratory. At the concentration of 100 ng/ml, recoveries of triazolam in plasma and urine were 84.9 and 91.0%, respectively. The coefficients of variation in terms of its recovery were 11.5 (plasma) and 10.2% (urine). The detection limit for quantitation by the method was approximately 5 ng/g. This method was applied to two autopsy cases, giving triazolam distribution in body fluids and organs. In one case (33-year-old woman), concentrations of triazolam in the heart blood, urine, brain, lung, liver, kidney, skeletal muscles and stomach contents were 83.9, 741, 106, 165, 507, 293, 125 and 343 ng/g, respectively. From these toxicological data together with autopsy findings, her cause of death was diagnosed as triazolam poisoning. In the other case (45-year-old man), triazolam concentrations in the urine and stomach contents were 7.81 and 41.1 ng/g, respectively, but it could not be detected in the pleural blood; his cause of death was judged to be a traumatic shock, based on autopsy findings.