Glecaprevir-Pibrentasvir and Ethinyl Estradiol-Induced Liver Injury in a Patient Without Cirrhosis

Most drug liver injury cases are the result of an unexpected interaction with medications. We present a 33-year-old woman, four months postpartum, on ethinyl estradiol/norgestrel, who presented in the ED with nausea, vomiting, abdominal pain, and severe pruritus six weeks after starting glecaprevir-pibrentasvir (GP) treatment. The patient was suspected to have a drug-induced liver injury (DILI), and GP was discontinued. Other potential causes of liver injury were ruled out via labs, imaging, and liver biopsy. The patient's liver function significantly improved after discontinuing GP. Few cases of DILI secondary to GP have been reported. However, to the best of our knowledge, DILI from the interaction of ethinyl estradiol and GP does not exist in published literature. In our case, DILI was likely due to the effect of GP and ethinyl estradiol on the liver's cytochrome 450 (CYP 450) system. The aim of this report is to raise awareness and improve pharmacovigilance, especially in patients receiving medications that are metabolized by the liver's CYP 450 system. Early detection of DILI secondary to drug-interaction and discontinuation of the culprit medication is the mainstay of treatment. However, there is a lack of evidence-based management strategies for premature discontinuation of GP in the setting of DILI while treating chronic hepatitis C virus (HCV) infection. Further investigations are warranted.

Investigating the association between CYP2J2 inhibitors and QT prolongation: a literature review

Drug withdrawal post-marketing due to cardiotoxicity is a major concern for drug developers, regulatory agencies, and patients. One common mechanism of cardiotoxicity is through inhibition of cardiac ion channels, leading to prolongation of the QT interval and sometimes fatal arrythmias. Recently, oxylipin signaling compounds have been shown to bind to and alter ion channel function, and disruption in their cardiac levels may contribute to QT prolongation. Cytochrome P450 2J2 (CYP2J2) is the predominant CYP isoform expressed in cardiomyocytes, where it oxidizes arachidonic acid to cardioprotective epoxyeicosatrienoic acids (EETs). In addition to roles in vasodilation and angiogenesis, EETs bind to and activate various ion channels. CYP2J2 inhibition can lower EET levels and decrease their ability to preserve cardiac rhythm. In this review, we investigated the ability of known CYP inhibitors to cause QT prolongation using Certara's Drug Interaction Database. We discovered that among the multiple CYP isozymes, CYP2J2 inhibitors were more likely to also be QT-prolonging drugs (by approximately 2-fold). We explored potential binding interactions between these inhibitors and CYP2J2 using molecular docking and identified four amino acid residues (Phe61, Ala223, Asn231, and Leu402) predicted to interact with QT-prolonging drugs. The four residues are located near the opening of egress channel 2, highlighting the potential importance of this channel in CYP2J2 binding and inhibition. These findings suggest that if a drug inhibits CYP2J2 and interacts with one of these four residues, then it may have a higher risk of QT prolongation and more preclinical studies are warranted to assess cardiovascular safety.

CYP1A inhibitors: Recent progress, current challenges, and future perspectives

Mammalian cytochrome P450 1A (CYP1A) are key phase I xenobiotic-metabolizing enzymes that play a distinctive role in metabolic activation or metabolic clearance of a variety of procarcinogens, drugs, and endogenous substances. Human CYP1A subfamily contains two members (hCYP1A1 and hCYP1A2), which are known to catalyze the oxidative activation of some environmental procarcinogens into carcinogenic species. Increasing evidence has demonstrated that CYP1A inhibitor therapies are promising strategies for cancer chemoprevention or overcoming CYP1A-associated drug toxicity and resistance. Herein, we reviewed recent advances in the discovery and characterization of hCYP1A inhibitors, from the discovery approaches to structural features and biomedical applications of hCYP1A inhibitors. The inhibition potentials, inhibition modes, and inhibition constants of all reported hCYP1A inhibitors are comprehensively summarized. Meanwhile, the structural features and structure-activity relationships of different classes of hCYP1A1 and hCYP1A2 inhibitors are analyzed and discussed in depth. Furthermore, the major challenges and future directions for this field are presented and highlighted. Collectively, the information and knowledge presented here will strongly facilitate the researchers to discover and develop more efficacious CYP1A inhibitors for specific purposes, such as chemo-preventive agents or as tool molecules in hCYP1A-related fundamental studies.

Interaction of a caffeine overdose with clinical doses of contraceptive ethinyl estradiol in a young woman

Aim

The overdose of caffeine, a cytochrome P450 1A2 probe, in young women has become a problem. The aim of this study was to evaluate possible drug interactions between intentionally overdosed caffeine (12 g) and oral contraceptive doses of ethinyl estradiol prescribed to a young woman in a suicide attempt.

Methods

The serum concentrations of caffeine in the patient and the time-dependent ethinyl estradiol inhibition of caffeine oxidation in vitro were evaluated.

Results

The serum concentration of caffeine 4 h after overdose was 136 μg/mL; from the data obtained between 4 and 28 h after overdose, the half-life was estimated to be 33 h, which is many times larger than the normal value. Prescribed ethinyl estradiol prolonged caffeine elimination in vivo and inhibited paraxanthine formation, as evidenced by the low serum concentrations. In human liver microsomes, ethinyl estradiol (50 nM) inhibited half of caffeine N 3 -demethylation. Pre-incubation of human liver microsomes with ethinyl estradiol resulted in a powerful time-dependent inhibitory effect on caffeine N 3 -demethylation in human liver microsomes.

Conclusion

These results suggest that a prescription history of contraceptives at clinical doses may have a strong effect on the pharmacokinetics of overdosed caffeine in young women, resulting in dangerous drug interactions.

Application of CYP1A2-Template System to Understand Metabolic Processes in the Safety Assessment

Cytochrome P450 (CYP)-mediated metabolisms of four chemicals have been investigated to understand their unresolved phenomena of their metabolisms using human CYP-Template systems developed in our previous studies (Drug Metab Pharmacokinet 2019, 2021, 2022). Simulation experiments of a topoisomerase-targeting agent, amonafide, offered a possible new inhibitory-mechanism as Trigger-residue inactivation on human CYP1A2 Template. N-Acetylamonafide as well as amonafide would inactivate CYP1A2 through the interference of Trigger-residue movement with their dimethylaminoethyl parts. The mechanism was also supported on the inhibition/inactivation of two other drugs, DSP-1053 and binimetinib. Both the drugs, after other CYP-mediated slight structural alterations, were expected to interact with Trigger-residue for the intense inhibition on CYP1A2 Template. Possible formation of reactive intermediates of amonafide and 3-methylindole was also examined on CYP1A2 Template. Placements of amonafide suggested the scare N-oxidation of the arylamine part due to the Trigger-residue interaction. Placements of 3-methylindole suggested the formation of a reactive intermediate, 3-methyleneindolenine, rather selectively on rodent CYP1A2 than on human CYP1A2, in consistent with the experimental data. These results suggest that CYP Template systems developed are effective tools to warn an appearance of unstable reactive intermediates. Our CYP-Template systems would support confident judgements in safety assessments through offering the mechanistic understandings of the metabolism.

Evaluation of the food effect on a drospirenone only contraceptive containing 4 mg administered with and without high-fat breakfast in a randomised trial

Background

The objective of the present trial was to assess the difference in pharmacokinetics (PK) of an oral test preparation containing 4 mg drospirenone (DRSP) under fasting conditions compared to PK upon food intake after single dose administration.

Methods

Open label, single centre, two-treatment, two-sequence, crossover study in 24 healthy female volunteers, with duration of 1 day per sequence and with a real wash-out period of 14 days to investigate the relative bioavailability of DRSP with both forms of administration. The 90% confidence intervals (CI) were calculated for the intra-individual ratio (test with food vs. without food) of the PK endpoints Area under the curve; 0–72 h [AUC(0-72 h₎] and maximal plasma concentration [Cmax] of DRSP.

Results

The 90% CI calculated by analysis of variance using logistic transformation (ANOVA-log) for the endpoint, intra-individual ratio (Test ‘A’ = with food intake) vs. Test ‘B’ = without food intake) of AUC(0-72 h) of drospirenone was between 104.72 and 111.36%. The 90% CI calculated by means of ANOVA- log for the endpoint intra-individual ratio (Test ‘A’ vs. Test ‘B’) of Cmax of DRSP was between 118.58 and 141.10%. The mean relative bioavailability of the test with food ‘A’ compared to the Test without food ‘B’ after single dose administration based on the endpoints AUC(0-72 h₎ was 107.99%; for the endpoint Cmax it was 129.35%.

Conclusions

The rate of absorption, based on the endpoint Cmax of DRSP was increased by about 30% under fed conditions. With respect to consumer habits, this may represent a relevant benefit for contraceptive safety, as the time span between food consumption and pill intake does not play a role.

Implications

Our results suggest that the food intake has no impact on the absorption of 4 mg DRSP in the management of contraception. This increases the contraceptive efficacy as no interference with food is expected when consuming the oral formulation under real life conditions.

Trail registration: Trial registration number: EudraCT-No: 2012–004,309-28.

Drug Interactions Involving 17α-Ethinylestradiol: Considerations Beyond Cytochrome P450 3A Induction and Inhibition

It is widely acknowledged that drug-drug interactions (DDIs) involving estrogen (17α-ethinylestradiol (EE))-containing oral contraceptives (OCs) are important. Consequently, sponsors of new molecular entities (NMEs) often conduct clinical studies with priority given to OCs as victims of cytochrome P450 (CYP) 3A (CYP3A) induction and inhibition. Such scenarios are reflected in the US Food and Drug Administration-issued guidance documentation related to OC DDI studies. Although CYP3A is important, OCs such as EE are metabolized by sulfotransferase 1E1 and UDP-glucuronosyltransferase (UGT) 1A1, expressed in the gut and liver, and so both can also serve as loci of victim OC DDI. Therefore, for any NME, one should carefully consider its induction and inhibition profile involving CYP3A4/5, UGT1A1, and SULT1E1. As DDI perpetrators, available clinical DDI data indicate that EE-containing OCs can induce (e.g., UGT1A4 and CYP2A6) and inhibit (CYP1A2 ≥ CYP2C19 > CYP3A4/5 > CYP2C8, CYP2B6, CYP2D6, and CYP2C9) various CYP forms. Although available in vitro CYP inhibition data do not explain such a graded inhibitory effect in vivo, it is hypothesized that EE differentially modulates CYP expression via potent agonism of the estrogen receptor expressed in the gut and liver. From the standpoint of the NME as potential OC DDI victim, therefore, it is important to assess its projected (pre-phase I) or known therapeutic index and pharmacokinetic profile (fraction absorbed, absolute oral bioavailability, clearance/extraction class, fraction metabolized by CYP1A2, CYP2C19, CYP2A6, and UGT1A4). Such information can enable the prioritization, design, and interpretation of NME-OC DDI studies.

Gynecological cancer among adolescents and young adults (AYA)

Adolescents and young adults (AYA) patients with cancer show specific biological, sociodemographic and behavioral features, with lower survival rates than younger group. Gynecologic malignancies that occur among AYA requires a multidisciplinary management and a tailored model of care, in order to enhance the early diagnosis, the adherence to the treatment, the enrollment in clinical trials, the rate of survival and the quality of life (QoL). In this article, we review the main gynecological tumors that may occur in AYA, with a focus on the clinical signs at the diagnosis and the modality of treatment. In addition, we proposed a model of multidisciplinary and personalized care for AYA with gynecological tumors, which can help the clinicians to manage the specific gynecologic concerns, such as ovarian failure, contraception, fertility, late psychosocial effects.

Clinical Pharmacology and Safety of Trifarotene, a First-in-Class RARγ-Selective Topical Retinoid

Trifarotene is a new drug with retinoic acid receptor activity and selectivity for retinoic acid receptor-γ. The reported studies aimed at assessing the clinical pharmacology and safety of trifarotene. The clinical pharmacology of topical trifarotene up to 100 µg/g was extensively investigated through 2 maximal usage pharmacokinetic trials (MUsT) conducted in adult (≥18 years) and pediatric patients (9-17 years) with moderate to severe acne and two studies conducted in healthy volunteers: 1 thorough QT_C study and 1 drug-drug interaction study with concomitantly administered oral levonorgestrel (0.15 mg)/ethinyl estradiol (0.03 mg). Safety assessments included adverse event reporting and assessment of erythema, scaling, dryness, and stinging/burning using a scale from 0 = none to 4 = severe, as well as the evaluation of the systemic safety of trifarotene through routine laboratory testing. Systemic absorption of trifarotene was generally unquantifiable in the target population, especially when applied at 50 µg/g. QT_C investigations did not show any risk of cardiovascular health issues; trifarotene did not reduce the systemic exposure to oral contraceptives such as levonorgestrel/ethinyl estradiol. Safety analyses did not show local or systemic safety concerns with trifarotene up 100 µg/g, a dose twice as high as the intended market dose. Results showed that trifarotene 50 µg/g cream is well tolerated and safe, even when applied under maximized conditions in adults and pediatric acne patients presenting with severe acne. Daily use of trifarotene 50 µg/g cream was not associated with cardiovascular effects and did not result in drug-drug interaction in women of childbearing potential using oral contraception.

Comparative pharmacokinetic estimates of drospirenone alone and in combination with ethinyl estradiol after single and repeated oral administration in healthy females

OBJECTIVE

To determine the pharmacokinetics (PK) of drospirenone (DRSP), alone versus in combination with ethinyl estradiol (EE), after single and repeated administration.

STUDY DESIGN

We conducted a single-centre, open-label, crossover, 2-treatment, 2-period, 2-sequence study in which non-micronized DRSP 4 mg or a combination of DRSP 3 mg and EE 0.02 mg were administered to healthy female subjects on day 1 to obtain a single-dose kinetic profile, and from day 4 to day 15 to obtain a repeated-dose kinetic profile. The maximum observed concentration (C_max) and area under the concentration/time curve (AUC) were determined in a model-independent way using non dose corrected data. Statistical analysis was based on a parametric method (ANOVA-log).

RESULTS

A total of 24 healthy female subjects were randomized 1:1 into the study. The mean relative, non-dose-corrected PK estimates after single-dose administration for the endpoints AUC_(0-72h), AUC_(0-24h) and C_max were 543.5 ng*h/mL, 296.1 ng*h/mL and 27.3 ng/mL for DRSP alone, and 442.0 ng*h/mL, 264.7 ng*h/mL and 37.5 ng/mL for the DRSP/EE combination; p < 0.001. The mean relative, non-dose-corrected PK estimates after repeated dose administration for the endpoints AUC_(0-72h), AUC_(0-24h) and C_max were 1066.8 ng*h/ml, 570.2 ng*h/mL and 41.0 ng/mL for DRSP alone, and 1394.5 ng*h/mL, 732.8 ng*h/mL and 61.4 ng/mL for the DRSP/EE combination; p < 0.001.

CONCLUSIONS

DRSP alone exhibits a lower accumulation ratio than together with EE. The extent of systemic exposure at steady-state is about 32% less with the new formulation (AUC_(0-24h), steady-state geometric mean ratio: 77.8%; 90% confidence interval: 74.6%-81.1%). This PK profile may be caused by EE.

IMPLICATIONS

Our results suggest that metabolic pathways of DRSP can be inhibited by EE resulting in higher DRSP plasma concentrations in DRSP/EE formulations than in a DRSP-alone formulation. The enzymes CYP3A4 and SULT1A1 may play a role. Additional drug-drug-interaction studies are needed to better understand these metabolic pathways and their future clinical implications.

Perspectives from the Innovation and Quality Consortium Induction Working Group on Factors Impacting Clinical Drug-Drug Interactions Resulting from Induction: Focus on Cytochrome 3A Substrates

A recent publication from the Innovation and Quality Consortium Induction Working Group collated a large clinical data set with the goal of evaluating the accuracy of drug-drug interaction (DDI) prediction from in vitro data. Somewhat surprisingly, comparison across studies of the mean- or median-reported area under the curve ratio showed appreciable variability in the magnitude of outcome. This commentary explores the possible drivers of this range of outcomes observed in clinical induction studies. While recommendations on clinical study design are not being proposed, some key observations were informative during the aggregate analysis of clinical data. Although DDI data are often presented using median data, individual data would enable evaluation of how differences in study design, baseline expression, and the number of subjects contribute. Since variability in perpetrator pharmacokinetics (PK) could impact the overall DDI interpretation, should this be routinely captured? Maximal induction was typically observed after 5-7 days of dosing. Thus, when the half-life of the inducer is less than 30 hours, are there benefits to a more standardized study design? A large proportion of CYP3A4 inducers were also CYP3A4 inhibitors and/or inactivators based on in vitro data. In these cases, using CYP3A selective substrates has limitations. More intensive monitoring of changes in area under the curve over time is warranted. With selective CYP3A substrates, the net effect was often inhibition, whereas less selective substrates could discern induction through mechanisms not susceptible to inhibition. The latter included oral contraceptives, which raise concerns of reduced efficacy following induction. Alternative approaches for modeling induction, such as applying biomarkers and physiologically based pharmacokinetic modeling (PBPK), are also considered. SIGNIFICANCE STATEMENT: The goal of this commentary is to stimulate discussion on whether there are opportunities to optimize clinical drug-drug interaction study design. The overall aim is to reduce, understand and contextualize the variability observed in the magnitude of induction across reported clinical studies. A large clinical CYP3A induction dataset was collected and further analyzed to identify trends and gaps. Reporting individual victim PK data, characterizing perpetrator PK and including additional PK assessments for mixed-mechanism perpetrators may provide insights into how these factors impact differences observed in clinical outcomes. The potential utility of biomarkers and PBPK modeling are discussed in considering future directions.

Alterations in Xenobiotic-Metabolizing Enzyme Activities across Menstrual Cycle in Healthy Volunteers

The purpose of the study was to determine whether the in vivo activities of drug-metabolizing enzymes CYP1A2 and CYP2A6, xanthine oxidase (XO), and N-acetyltransferase-2 (NAT2) vary across the menstrual cycle. Forty-two healthy women were studied at early follicular phase (EFP: 2nd to 4th days), late follicular phase (LFP: 10th to 12th days), and luteal phase (LP: 19th to 25th days) of a single menstrual cycle, and blood and urine samples were collected at each phase. Spot urine samples obtained 6 hours following 200-mg caffeine administration were used to determine caffeine metabolite ratios (CMRs); blood samples were used to determine CYP1A2*1F (rs762551) and CYP1A2*1C (rs2069514) polymorphisms and the hormonal profile (estradiol, progesterone, and luteinizing and follicle-stimulating hormones) at EFP, LFP, and LP. CMR and hormone variations were analyzed at three levels (EFP, LFP, LP) using one-way repeated-measures analysis of variance. CYP1A2 activity was lower and that of CYP2A6 and NAT2 were higher at LFP compared with EFP and LP. Enzyme alterations were significant in volunteers (n = 21) whose hormonal profiles at EFP, LFP, and LP corresponded to expected levels, but not in volunteers (n = 15) with presumed early or late sampling around LFP. No significant difference was detected in any enzyme activity in presumed anovulatory volunteers (n = 6). The reduction of CYP1A2 activity at LFP was not associated with smoking or CYP1A2*1F polymorphism. XO and NAT2 (fast acetylators) activities remained unaltered. It is suggested that drug-metabolizing enzyme activities are altered across the menstrual cycle. Selection of appropriate sampling periods verified by hormonal assessment and identification of anovulatory cycles are decisive factors in disclosing altered enzyme activity across the menstrual cycle.

Exposure to endocrine disruptors 17alpha-ethinylestradiol and estradiol influences cytochrome P450 1A1-mediated genotoxicity of benzo[a]pyrene and expression of this enzyme in rats

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17α-ethinylestradiol (EE2) and estradiol affect genotoxicity of benzo[a]pyrene (BaP) in rats.

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Cytochrome P450 (CYP) 1A1 and 1B1 are induced in rats by BaP but not EE2 and estradiol.

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Exposure of rats to EE2, estradiol and BaP decreased BaP-DNA adduct formation in vivo.

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The decrease results from inhibition of CYP1A1-mediated BaP activation by EE2 and estradiol.

Endocrine disruptors (EDs) are compounds that interfere with the balance of the endocrine system by mimicking or antagonising the effects of endogenous hormones, by altering the synthesis and metabolism of natural hormones, or by modifying hormone receptor levels. The synthetic estrogen 17α-ethinylestradiol (EE2) and the environmental carcinogen benzo[a]pyrene (BaP) are exogenous EDs whereas the estrogenic hormone 17β-estradiol is a natural endogenous ED. Although the biological effects of these individual EDs have partially been studied previously, their toxicity when acting in combination has not yet been investigated. Here we treated Wistar rats with BaP, EE2 and estradiol alone or in combination and studied the influence of EE2 and estradiol on: (i) the expression of cytochrome P450 (CYP) 1A1 and 1B1 in rat liver on the transcriptional and translational levels; (ii) the inducibility of these CYP enzymes by BaP in this rat organ; (iii) the formation of BaP-DNA adducts in rat liver in vivo; and (iv) the generation of BaP-induced DNA adducts after activation of BaP with hepatic microsomes of rats exposed to BaP, EE2 and estradiol and with recombinant rat CYP1A1 in vitro. BaP acted as a strong and moderate inducer of CYP1A1 and 1B1 in rat liver, respectively, whereas EE2 or estradiol alone had no effect on the expression of these enzymes. However, when EE2 was administered to rats together with BaP, it significantly decreased the potency of BaP to induce CYP1A1 and 1B1 gene expression. For EE2, but not estradiol, this also correlated with a reduction of BaP-induced CYP1A1 enzyme activity in rat hepatic microsomes. Further, while EE2 and estradiol did not form covalent adducts with DNA, they affected BaP-derived DNA adduct formations in vivo and in vitro. The observed decrease in BaP-DNA adduct levels in rat liver in vivo resulted from the inhibition of CYP1A1-mediated BaP bioactivation by EE2 and estradiol. Our results indicate that BaP genotoxicity mediated through its activation by CYP1A1 in rats in vivo is modulated by estradiol and its synthetic derivative EE2.

Formation of Both Heme and Apoprotein Adducts Contributes to the Mechanism-Based Inactivation of Human CYP2J2 by 17α-Ethynylestradiol

17α-Ethynylestradiol (EE), a major component of many oral contraceptives, affects the activities of a number of the human cytochrome P450 (P450) enzymes. Here, we characterized the effect of EE on CYP2J2, a major human P450 isoform that participates in metabolism of arachidonic acid. EE inactivated the hydroxyebastine carboxylation activity of CYP2J2 in a reconstituted system. The loss of activity is time and concentration dependent and requires NADPH. The K_I and k_inact values for the inactivation were 3.6 μM and 0.08 minute^-1, respectively. Inactivation of CYP2J2 by EE was due to formation of a heme adduct as well as an apoprotein adduct. Mass spectral analysis of CYP2J2 partially inactivated by EE showed two distinct protein masses in the deconvoluted spectrum that exhibited a mass difference of approximately 312 Da, which is equivalent to the sum of the mass of EE and one oxygen atom. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis revealed a heme adduct with MH⁺ ion at m/z 875.5, corresponding to alkylation of an iron-depleted prosthetic heme by EE plus one oxygen atom. The reactive intermediate responsible for covalently modifying both the prosthetic heme and apoprotein was characterized by trapping with glutathione (GSH). LC-MS/MS analysis revealed two GSH conjugate isomers with MH⁺ ions at m/z 620, which were formed by reaction between GSH and EE with the oxygen being added to either the internal or terminal carbon of the ethynyl moiety. High-pressure liquid chromatography analysis revealed that three other major metabolites were formed during EE metabolism by CYP2J2.

The Safety of Ingested Caffeine: A Comprehensive Review

Caffeine is the most widely consumed psychoactive drug in the world. Natural sources of caffeine include coffee, tea, and chocolate. Synthetic caffeine is also added to products to promote arousal, alertness, energy, and elevated mood. Over the past decade, the introduction of new caffeine-containing food products, as well as changes in consumption patterns of the more traditional sources of caffeine, has increased scrutiny by health authorities and regulatory bodies about the overall consumption of caffeine and its potential cumulative effects on behavior and physiology. Of particular concern is the rate of caffeine intake among populations potentially vulnerable to the negative effects of caffeine consumption: pregnant and lactating women, children and adolescents, young adults, and people with underlying heart or other health conditions, such as mental illness. Here, we review the research into the safety and safe doses of ingested caffeine in healthy and in vulnerable populations. We report that, for healthy adults, caffeine consumption is relatively safe, but that for some vulnerable populations, caffeine consumption could be harmful, including impairments in cardiovascular function, sleep, and substance use. We also identified several gaps in the literature on which we based recommendations for the future of caffeine research.

Inhibition and inactivation of human CYP2J2: Implications in cardiac pathophysiology and opportunities in cancer therapy

Extrahepatic cytochrome P450 enzymes (CYP450) are pivotal in the metabolism of endogenous substrates and xenobiotics. CYP2J2 is a major cardiac CYP450 and primarily metabolizes polyunsaturated fatty acids such as arachidonic acid to cardioactive epoxyeicosatrienoic acids. Due to its role in endobiotic metabolism, CYP2J2 has been actively studied in recent years with the focus on its biological functions in cardiac pathophysiology. Additionally, CYP2J2 metabolizes a number of xenobiotics such as astemizole and terfenadine and is potently inhibited by danazol and telmisartan. Notably, CYP2J2 is found to be upregulated in multiple cancers. Hence a number of specific CYP2J2 inhibitors have been developed and their efficacy in inhibiting tumor progression has been actively studied. CYP2J2 inhibitor such as C26 (1-[4-(vinyl)phenyl]-4-[4-(diphenyl-hydroxymethyl)-piperidinyl]-butanone hydrochloride) caused marked reduction in tumor proliferation and migration as well as promoted apoptosis in cancer cells. In this review, we discuss the role of CYP2J2 in cardiac pathophysiology and cancer therapeutics. Additionally, we provide an update on the substrates, reversible inhibitors and irreversible inhibitors of CYP2J2. Finally, we discuss the current gaps and future directions in CYP2J2 research.

Role of Cytochrome P450 2C8 in Drug Metabolism and Interactions

During the last 10-15 years, cytochrome P450 (CYP) 2C8 has emerged as an important drug-metabolizing enzyme. CYP2C8 is highly expressed in human liver and is known to metabolize more than 100 drugs. CYP2C8 substrate drugs include amodiaquine, cerivastatin, dasabuvir, enzalutamide, imatinib, loperamide, montelukast, paclitaxel, pioglitazone, repaglinide, and rosiglitazone, and the number is increasing. Similarly, many drugs have been identified as CYP2C8 inhibitors or inducers. In vivo, already a small dose of gemfibrozil, i.e., 10% of its therapeutic dose, is a strong, irreversible inhibitor of CYP2C8. Interestingly, recent findings indicate that the acyl-β-glucuronides of gemfibrozil and clopidogrel cause metabolism-dependent inactivation of CYP2C8, leading to a strong potential for drug interactions. Also several other glucuronide metabolites interact with CYP2C8 as substrates or inhibitors, suggesting that an interplay between CYP2C8 and glucuronides is common. Lack of fully selective and safe probe substrates, inhibitors, and inducers challenges execution and interpretation of drug-drug interaction studies in humans. Apart from drug-drug interactions, some CYP2C8 genetic variants are associated with altered CYP2C8 activity and exhibit significant interethnic frequency differences. Herein, we review the current knowledge on substrates, inhibitors, inducers, and pharmacogenetics of CYP2C8, as well as its role in clinically relevant drug interactions. In addition, implications for selection of CYP2C8 marker and perpetrator drugs to investigate CYP2C8-mediated drug metabolism and interactions in preclinical and clinical studies are discussed.

Pharmacokinetic interaction between the CYP3A4 inhibitor ketoconazole and the hormone drospirenone in combination with ethinylestradiol or estradiol

AIMS

The present study was conducted to investigate the influence of the strong CYP3A4 inhibitor ketoconazole (KTZ) on the pharmacokinetics of drospirenone (DRSP) administered in combination with ethinylestradiol (EE) or estradiol (E2).

METHODS

This was a randomized, multicentre, open label, one way crossover, fixed sequence study with two parallel treatment arms. A group sequential design allowed terminating the study for futility after first study cohort. About 50 healthy young women were randomized 1 : 1 to 'DRSP/EE' or 'DRSP/E2'. Subjects in the 'DRSP/EE' group received DRSP 3 mg/EE 0.02 mg (YAZ®, Bayer) once daily for 21 to 28 days followed by DRSP 3 mg/EE 0.02 mg once daily plus KTZ 200 mg twice daily for 10 days. Subjects in the 'DRSP/E2' group received DRSP 3 mg/E2 1.5 mg (research combination) once daily for 21 to 28 days followed by DRSP 3 mg/E2 1.5 mg once daily plus KTZ 200 mg twice daily for 10 days.

RESULTS

Oral co-administration of DRSP/EE or DRSP/E2 and KTZ resulted in an increase in DRSP exposure (AUC(0,24 h)) in both treatment groups: DRSP/EE group: 2.68-fold DRSP increase (90% CI 2.44, 2.95); DRSP/E2 group: 2.30-fold DRSP increase (90% CI 2.08, 2.54). EE and estrone (metabolite of E2) exposures were increased ~1.4-fold whereas E2 exposure was largely unaffected by KTZ co-administration.

CONCLUSIONS

A moderate pharmacokinetic drug-drug interaction between DRSP and KTZ was demonstrated in this study. No relevant changes of medical concern were detected in the safety data collected in this study.

Clozapine toxicity due to a multiple drug interaction: a case report

Introduction

We report the case of a multiple drug interaction involving clozapine, antifungals and oral contraceptives, which resulted in an increased clozapine plasma level, pericarditis with pericardial effusion and eosinophilia in a young Caucasian woman. These symptoms and signs disappeared a few days after discontinuation of clozapine. At present, we are not aware of reports of clozapine–antifungals interaction, whereas there is only one other case report on the interaction between oral contraceptives and clozapine. The purpose of this case report is to show the risk of potentially serious adverse effects stemming from drug interactions involving medications routinely used in clinical practice.

Case presentation

A 29-year-old Caucasian woman diagnosed with a schizoaffective disorder was admitted to a psychiatric unit for acute psychosis (hallucinations, delusions and catatonic behavior). She denied smoking tobacco products and was on long-term oral contraceptives. During the first month of hospitalization she was treated with antipsychotics and for 1 week she took simultaneously fluconazole and miconazole gel, after being diagnosed with oral candidiasis. On the last day of antifungals treatment, 29 days after admission, clozapine was started with resolution of psychotic symptoms. After 3 weeks, her clozapine plasma level had increased to 542ng/mL and eosinophilia was observed. She complained of nausea, vomiting and palpitations; echocardiography showed echocardiographic abnormalities and pericardial effusion. Oral contraceptives were discontinued and after 1 week clozapine was interrupted, with a complete resolution of side effects and pericardial effusion within 4 days.

Conclusions

Clozapine is metabolized by cytochrome P450. The use of inhibitors or other substrates of cytochrome P450, such as antifungals and oral contraceptives, can cause long-lasting interactions and clozapine toxicity. The Naranjo algorithm shows clozapine is a definite cause of pericarditis (score 9) and both clozapine–antifungals and clozapine–contraceptives interactions resulted probable (score 5) in Drug Interaction Probability Scale. A good knowledge on drugs that act as substrates, inhibitors or inducers of cytochrome P450 is mandatory. When those drugs are used in patients taking clozapine, blood level monitoring of clozapine should be recommended, since a lower dose of clozapine might be required to prevent clozapine toxicity.

Pharmacotherapy for mood disorders in pregnancy: a review of pharmacokinetic changes and clinical recommendations for therapeutic drug monitoring

OBJECTIVE

Pharmacotherapy for mood disorders during pregnancy is often complicated by pregnancy-related pharmacokinetic changes and the need for dose adjustments. The objectives of this review are to summarize the evidence for change in perinatal pharmacokinetics of commonly used pharmacotherapies for mood disorders, discuss the implications for clinical and therapeutic drug monitoring (TDM), and make clinical recommendations.

METHODS

The English-language literature indexed on MEDLINE/PubMed was searched for original observational studies (controlled and uncontrolled, prospective and retrospective), case reports, and case series that evaluated or described pharmacokinetic changes or TDM during pregnancy or the postpartum period.

RESULTS

Pregnancy-associated changes in absorption, distribution, metabolism, and elimination may result in lowered psychotropic drug levels and possible treatment effects, particularly in late pregnancy. Mechanisms include changes in both phase 1 hepatic cytochrome P450 and phase 2 uridine diphosphate glucuronosyltransferase enzyme activities, changes in hepatic and renal blood flow, and glomerular filtration rate. Therapeutic drug monitoring, in combination with clinical monitoring, is indicated for tricyclic antidepressants and mood stabilizers during the perinatal period.

CONCLUSIONS

Substantial pharmacokinetic changes can occur during pregnancy in a number of commonly used antidepressants and mood stabilizers. Dose increases may be indicated for antidepressants including citalopram, clomipramine, imipramine, fluoxetine, fluvoxamine, nortriptyline, paroxetine, and sertraline, especially late in pregnancy. Antenatal dose increases may also be needed for lithium, lamotrigine, and valproic acid because of perinatal changes in metabolism. Close clinical monitoring of perinatal mood disorders and TDM of tricyclic antidepressants and mood stabilizers are recommended.

An ethinyl estradiol-levonorgestrel containing oral contraceptive does not alter cytochrome P4502C9 in vivo activity

Oral contraceptives have been in wide use for more than 50 years. Levonorgestrel, a commonly employed progestin component of combined oral contraceptives, was implicated in drug-drug interactions mediated via CYP2C9. Although in vitro studies refuted this interaction, there are no confirmatory in vivo studies. In the current study, we examined the phenotypic status of CYP2C9 using low-dose (125 mg) tolbutamide before and after oral contraceptive use in reproductive age women. Blood was collected 24 hours after the tolbutamide oral dose was administered, plasma was isolated, and tolbutamide concentration (C24) was measured using liquid chromatography-mass spectrometry. The natural logarithm of tolbutamide C24, a metric for CYP2C9 phenotype, was found to be equivalent (within 80%-125% equivalency boundaries) before and after oral contraceptive use. In conclusion, levonorgestrel-containing oral contraceptives, the most commonly used form of oral contraception, do not affect the status of the CYP2C9 enzyme. This suggests that it is safe to co-administer levonorgestrel-containing oral contraceptives and CYP2C9 substrates, which include a wide array of drugs.

Cytochrome P450 family 1 inhibitors and structure-activity relationships

With the widespread use of O-alkoxyresorufin dealkylation assays since the 1990s, thousands of inhibitors of cytochrome P450 family 1 enzymes (P450s 1A1, 1A2, and 1B1) have been identified and studied. Generally, planar polycyclic molecules such as polycyclic aromatic hydrocarbons, stilbenoids, and flavonoids are considered to potentially be effective inhibitors of these enzymes, however, the details of the structure-activity relationships and selectivity of these inhibitors are still ambiguous. In this review, we thoroughly discuss the selectivity of many representative P450 family 1 inhibitors reported in the past 20 years through a meta-analysis.

Characterization and expression of cytochrome p450 cDNA (CYP9AT2) in Chironomus riparius fourth instar larvae exposed to multiple xenobiotics

We identified and characterized a CYP9 family gene, CrCYP9AT2, from Chironomus riparius, an eco-toxicologically important model organism. The 1978 base pair (bp) length CrCYP9AT2 cDNA has an open reading frame of 1587 bp encoding a putative 528 amino acid protein. There was 267 bp 5' and 123 bp 3' untranslated region with a polyadenylation signal site (AATAAA). The putative heme-binding cysteine at position 471 and the typical p450 signature sequence of 463-FGIGPRNCIG-473 were also present. The CrCYP9AT2 transcript was present in all life stages with the highest expression in larvae. The modulation of CrCYP9AT2 was studied using real-time polymerase chain reaction after 24h exposure to cadmium chloride, benzo(a)pyrene; bisphenol A; nonylphenol; chlorpyrifos and ethinylestradiol. Significant up-regulation of CrCYP9AT2 gene was observed after exposure to Cd, B(a)P and CP. However, CrCYP9AT2 was significantly down-regulated after exposure to BPA, NP and EE.

Docking-based virtual screening of covalently binding ligands: an orthogonal lead discovery approach

In pharmaceutical industry, lead discovery strategies and screening collections have been predominantly tailored to discover compounds that modulate target proteins through noncovalent interactions. Conversely, covalent linkage formation is an important mechanism for a quantity of successful drugs in the market, which are discovered in most cases by hindsight instead of systematical design. In this article, the implementation of a docking-based virtual screening workflow for the retrieval of covalent binders is presented considering human cathepsin K as a test case. By use of the docking conditions that led to the best enrichment of known actives, 44 candidate compounds with unknown activity on cathepsin K were finally selected for experimental evaluation. The most potent inhibitor, 4-(N-phenylanilino)-6-pyrrolidin-1-yl-1,3,5-triazine-2-carbonitrile (CP243522), showed a K(i) of 21 nM and was confirmed to have a covalent reversible mechanism of inhibition. The presented approach will have great potential in cases where covalent inhibition is the desired drug discovery strategy.

Construction of a CYP2E1-template system for prediction of the metabolism on both site and preference order

We have constructed an in silico system for the prediction of CYP2E1-mediated reaction using a two-dimensional template derived from substrate structures. Although CYP2E1 prefers small-size molecules for the substrates, the enzyme mediates oxidations of large-size molecules, such as benzo[a]pyrene. Overlays of these substrates, to assemble their sites of oxidation into a specific area, suggested a range of regions frequently occupied. The region, having a benzo[a]pyrene-like shape, was thus used as a CYP2E1 template. In this system, atoms in substrates, except for hydrogen atoms, were placed on corners of honeycomb structures of the template after having expanded the structures. Using published data for the metabolism on more than 80 substrates of CYP2E1, the core template was further refined to verify the adjacent area and to define the relative contribution of template positions for the catalysis. The positions on the template were classified into four different point (0-3) groups, depending on relative usage. In addition, we set independent points (-5 to 3) for specific positions to incorporate three-dimensional or functional information. Total scores from both position-occupancy and -function points were calculated for all the orientations of possible conformers of test substrates, and the scores were found to predict the relative abundance (i.e., order) as well as the regioselectivity of human CYP2E1 reactions with high fidelities.

Anhedonia in postpartum rats

Postpartum depression (PPD) is a debilitating illness, yet little is known about its causes. The purpose of this study was to examine a major symptom of depression during the postpartum period, anhedonia, by comparing sucrose preference in female rats that had undergone actual pregnancy or hormone-simulated pregnancy (HSP) to their respective controls. Whereas HSP rats showed significantly less preference than vehicle control rats for 1% sucrose solution during the first three weeks of the "postpartum" period, previously pregnant females showed only slightly depressed sucrose preference for the first 1-2 days postpartum, compared to non-pregnant controls. Habituation to 1% sucrose during the pregnancy period, which increased preference upon later testing in previously pregnant rats tested on postpartum day 2, did not significantly increase preference in HSP rats, suggesting that depressed preference in the latter group was not due to neophobia. Pre-treatment with desipramine did not prevent suppressed sucrose preference in HSP rats, and preference was even further suppressed following chronic sertraline treatment. These results suggest that estradiol withdrawal following HSP may cause anhedonia during the early "postpartum" period. In contrast, females that have undergone actual pregnancy are less likely to show this effect, suggesting that postpartum hormonal changes other than the dramatic decline in estradiol may buffer its negative mood effects.