Role of Cytochrome P450 2C9 in COVID-19 Treatment: Current Status and Future Directions.

The major human liver drug metabolising cytochrome P450 (CYP) enzymes are downregulated during inflammation and infectious disease state, especially during coronavirus disease 2019 (COVID-19) infection. The influx of proinflammatory cytokines, known as a 'cytokine storm', during severe COVID-19 leads to the downregulation of CYPs and triggers new cytokine release, which further dampens CYP expression. Impaired drug metabolism, along with the inevitable co-administration of drugs or 'combination therapy' in patients with COVID-19 with various comorbidities, could cause drug-drug interactions, thus worsening the disease condition. Genetic variability or polymorphism in CYP2C9 across different ethnicities could contribute to COVID-19 susceptibility. A number of drugs used in patients with COVID-19 are inducers or inhibitors of, or are metabolised by, CYP2C9, and co-administration might cause pharmacokinetic and pharmacodynamic interactions. It is also worth mentioning that some of the COVID-19 drug interactions are due to altered activity of other CYPs including CYP3A4. Isoniazid/rifampin for COVID-19 and tuberculosis co-infection; lopinavir/ritonavir and cobicistat/remdesivir combination therapy; or multi-drug therapy including ivermectin, azithromycin, montelukast and acetylsalicylic acid, known as TNR4 therapy, all improved recovery in patients with COVID-19. However, a combination of CYP2C9 inducers, inhibitors or both, and plausibly different CYP isoforms could lead to treatment failure, hepatotoxicity or serious side effects including thromboembolism or bleeding, as observed in the combined use of azithromycin/warfarin. Further, herbs that are CYP2C9 inducers and inhibitors, showed anti-COVID-19 properties, and in silico predictions postulated that phytochemical compounds could inhibit SARS-CoV-2 virus particles. COVID-19 vaccines elicit immune responses that activate cytokine release, which in turn suppresses CYP expression that could be the source of compromised CYP2C9 drug metabolism and the subsequent drug-drug interaction. Future studies are recommended to determine CYP regulation in COVID-19, while recognising the involvement of CYP2C9 and possibly utilising CYP2C9 as a target gene to tackle the ever-mutating SARS-CoV-2.

Variations in prothrombin time-international normalized ratio caused by drug-drug interaction in patients receiving warfarin: A retrospective observational study.

OBJECTIVES: Drug-drug interactions between warfarin and cytochrome P450 (CYP) 2C9 inhibitors and inducers are well known. Few studies have clarified the clinical impact of CYP2C9 inhibitors and inducers on warfarin therapy. Here, we evaluated the clinical impact of CYP2C9-mediated interactions on the pharmacodynamics of warfarin. MATERIALS AND METHODS: This retrospective observational study enrolled patients who received warfarin between 2008 and 2020 at Mie University Hospital. We defined prothrombin time-international normalized ratio/daily warfarin dose (PT-INR/dose) as the primary outcome and conducted a multiple linear regression analysis to clarify the factors that affected the primary outcome. Additionally, we examined the clinical features of patients who received CYP2C9 inducers. RESULTS: Out of 1,393 patients, 17 (1.2%) received carbamazepine, rifampicin, phenobarbital, or phenytoin as CYP2C9 inducers. Multiple linear regression analysis indicated that age, body mass index (BMI), serum albumin (Alb), estimated glomerular filtration rate (eGFR), and CYP2C9 inducers were associated with PT-INR/dose. The multiple regression equation was as follows: PT-INR/dose = 1.590 + 0.004 × age - 0.020 × BMI - 0.141 × Alb - 0.001 × eGFR - 0.149 × (if concomitant use of CYP2C9 inducers) (adjusted coefficient of determination = 0.106, Akaike information criterion = 267.3, p < 0.001). In patients receiving CYP2C9 inducers, lower PT-INR/dose values were observed regardless of co-administered CYP2C9 inhibitors. CONCLUSION: In addition to age, BMI, Alb, and eGFR, concomitant use of CYP2C9 inducers should be considered when adjusting the warfarin dose and PT-INR.

Pharmacokinetic Herb-Drug Interactions of Glipizide with Andrographis paniculata (Burm. f.) and Andrographolide in Normal and Diabetic Rats by Validated HPLC Method.

Co-administered medicinal herbs can modify a drug's pharmacokinetics (PK), effectiveness, and toxicity. Andrographis paniculata (Burm. f.) ethanolic extract (APE) and andrographolide (AND) (a potent CYP2C9 inducer/inhibitor) can alter the pharmacokinetic parameters of glipizide (GLZ). This study aimed to determine the potential pharmacokinetics of herb−drug interactions between GLZ and APE/AND in the plasma of normal and diabetic rats using the HPLC bioanalysis method. The glipizide bioanalytical method established with RP-HPLC/UV instrument was validated following the EMA guidelines. GLZ was administered alone and in combination with APE or AND to normal and diabetic rats. The GLZ pharmacokinetic parameters were estimated according to the correlation between concentration and sampling time using the PK solver program. A simple and rapid GLZ bioanalysis technique with a lower limit of quantitation of 25 ng/mL was developed and presented the following parameters: accuracy (error ≤ 15%), precision (CV ≤ 15%), selectivity, stability, and linearity (R2 = 0.998) at concentrations ranging 25−1500 ng/mL. APE administration significantly improved the Cmax and AUC0−t/AUC0−∞ GLZ values in normal and diabetic rats (p < 0.05). AND significantly reduced the bioavailability of GLZ in diabetic rats with small values of T 1/2, Cmax, and AUC0−t/AUC0−∞ (p < 0.05). This combination can be considered in administering medications because it can influence the pharmacological effects of GLZ.

S-warfarin limited sampling strategy with a population pharmacokinetic approach to estimate exposure and cytochrome P450 (CYP) 2C9 activity in healthy adults.

PURPOSE: S-warfarin is used to phenotype cytochrome P450 (CYP) 2C9 activity. This study evaluated S-warfarin limited sampling strategy with a population pharmacokinetic (PK) approach to estimate CYP2C9 activity in healthy adults. METHODS: In 6 previously published studies, a single oral dose of warfarin 10 mg was administered alone or with a CYP2C9 inducer to 100 healthy adults. S-warfarin concentrations were obtained from adults during conditions when subjects were not on any prescribed medications. A population PK model was developed using non-linear mixed effects modeling. Limited sampling models (LSMs) using single- or 2-timepoint concentrations were compared with full PK profiles from intense sampling using empiric Bayesian post hoc estimations of S-warfarin AUC derived from the population PK model. Preset criterion for LSM selection and validation were a correlation coefficient (R2) >0.9, relative percent mean prediction error (%MPE) >-5 to <5%, relative percent mean absolute error (%MAE) ≤ 10%, and relative percent root mean squared error (%RMSE) ≤ 15%. RESULTS: S-warfarin concentrations (n=2540) were well described with a two-compartment model. Mean apparent oral clearance was 0.56 L/hr and volume of distribution was 35.5 L. Clearance decreased 33% with the CYP2C9 *3 allele and increased 42% with lopinavir/ritonavir co-administration. During CYP2C9 constitutive conditions, LSMs at 48 hr and at 72 hr as well as 2-timepoint LSMs were within acceptable limits for R2, %MPE, %MAE, and %RMSE. During CYP2C9 induction, S-warfarin LSMs had unacceptable %MPE, %MAE, and %RMSE. CONCLUSIONS: Phenotyping studies with S-warfarin in healthy subjects can utilize a single- and/or a 2-timepoint LSM with a population PK approach to estimate constitutive CYP2C9 activity.

Risk of CYP2C9 induction analyzed by a relative factor approach with human hepatocytes.

By using the Relative Factor (RF) method-a method that can simply assess cytochrome P450 (CYP) induction risk based on a maximum induction effect model-we evaluated the risk of CYP2C9 induction and examined its relationship with risk of CYP3A4 induction. In cryopreserved human hepatocytes, the magnitude of CYP2C9 induction by eight drugs known to induce CYP3A4 was lower than the magnitude of CYP3A4 induction, but the magnitudes of induction of both were correlated. The RF values determined for CYP2C9 had a one-to-one linear relationship with values determined for CYP3A4, supporting reports that the induction mechanism of both enzymes is the same. Furthermore, clinical CYP2C9 induction data of compounds reported to induce CYP2C9 clinically were shown to be lower than those of CYP3A4. The thresholds for CYP2C9 induction risk assessment by the RF approach were determined to be at higher steady-state plasma concentrations than those for CYP3A4. Based on these results, induction of CYP2C9 was correlated with that of CYP3A4, and induction risk could be evaluated by the RF method using hepatocytes. The CYP2C9 induction risk of a compound was confirmed to be lower than its CYP3A4 induction risk.

Drug-drug interactions in an era of multiple anticoagulants: a focus on clinically relevant drug interactions.

Oral anticoagulants are commonly prescribed but high risk to cause adverse events. Skilled drug interaction management is essential to ensure safe and effective use of these therapies. Clinically relevant interactions with warfarin include drugs that modify cytochrome 2C9, 3A4, or both. Drugs that modify p-glycoprotein may interact with all direct oral anticoagulants, and modifiers of cytochrome 3A4 may interact with rivaroxaban and apixaban. Antiplatelet agents, nonsteroidal anti-inflammatory drugs, and serotonergic agents, such as selective serotonin reuptake inhibitors, can increase risk of bleeding when combined with any oral anticoagulant, and concomitant use should be routinely assessed. New data on anticoagulant drug interactions are available almost daily, and therefore, it is vital that clinicians regularly search interaction databases and the literature for updated management strategies. Skilled drug interaction management will improve outcomes and prevent adverse events in patients taking oral anticoagulants.

Pharmacokinetic/pharmacodynamic drug-drug interactions of avatrombopag when coadministered with dual or selective CYP2C9 and CYP3A interacting drugs.

AIMS: Avatrombopag, a thrombopoietin receptor agonist, is a substrate of cytochrome P450 (CYP) 2C9 and CYP3A. We assessed three drug-drug interactions of avatrombopag as a victim with dual or selective CYP2C9/3A inhibitors and inducers. METHODS: This was a three-part, open-label study. Forty-eight healthy subjects received single 20 mg doses of avatrombopag alone or with one of 3 CYP2C9/3A inhibitors or inducers: fluconazole 400 mg once daily for 16 days, itraconazole 200 mg twice daily on Day 1 and 200 mg once daily on Days 2-16, or rifampicin 600 mg once daily for 16 days. Pharmacokinetics, pharmacodynamics (platelet count) and safety of avatrombopag were evaluated. RESULTS: Coadministration of a single 20-mg dose of avatrombopag with fluconazole at steady-state resulted in 2.16-fold increase of AUC of avatrombopag, prolonged terminal elimination phase half-life (from 19.7 h to 39.9 h) and led to a clinically significant increase in maximum platelet count (1.66-fold). Itraconazole had a mild increase on both avatrombopag pharmacokinetics and pharmacodynamics compared to fluconazole. Coadministration of rifampicin caused a 0.5-fold decrease in AUC and shortened terminal elimination phase half-life (from 20.3 h to 9.84 h), but has no impact on maximum platelet count. Coadministration with interacting drugs was found to be generally safe and well-tolerated. CONCLUSIONS: The results from coadministration of fluconazole or itraconazole suggest that CYP2C9 plays a more predominant role in metabolic clearance of avatrombopag than CYP3A. To achieve comparable platelet count increases when avatrombopag is coadministered with CYP3A and CYP2C9 inhibitors, an adjustment in the dose or duration of treatment is recommended, while coadministration with strong inducers is not currently recommended.

Aprepitant and fosaprepitant drug interactions: a systematic review.

AIMS: Aprepitant and fosaprepitant, commonly used for the prevention of chemotherapy-induced nausea and vomiting, alter cytochrome P450 activity. This systematic review evaluates clinically significant pharmacokinetic drug interactions with aprepitant and fosaprepitant and describes adverse events ascribed to drug interactions with aprepitant or fosaprepitant. METHODS: We systematically reviewed the literature to September 11, 2016, to identify articles evaluating drug interactions involving aprepitant/fosaprepitant. The clinical significance of each reported pharmacokinetic drug interaction was evaluated based on the United States Food and Drug Administration guidance document on conducting drug interaction studies. The probability of an adverse event reported in case reports being due to a drug interaction with aprepitant/fosaprepitant was determined using the Drug Interaction Probability Scale. RESULTS: A total of 4377 publications were identified. Of these, 64 met inclusion eligibility criteria: 34 described pharmacokinetic drug interactions and 30 described adverse events ascribed to a drug interaction. Clinically significant pharmacokinetic interactions between aprepitant/fosaprepitant and bosutinib PO, cabazitaxel IV, cyclophosphamide IV, dexamethasone PO, methylprednisolone IV, midazolam PO/IV, oxycodone PO and tolbutamide PO were identified, as were adverse events resulting from an interaction between aprepitant/fosaprepitant and alcohol, anthracyclines, ifosfamide, oxycodone, quetiapine, selective serotonin reuptake inhibitors/serotonin-norepinephrine reuptake inhibitors and warfarin. CONCLUSIONS: The potential for a drug interaction with aprepitant and fosaprepitant should be considered when selecting antiemetic therapy.

Delayed de-induction of CYP2C9 compared to CYP3A after discontinuation of rifampicin: Report of two cases
.

OBJECTIVE: Timely dose reduction of concomitant medications is important after withdrawal of rifampicin, a CYP inducer. However, little is known about the differences in the time course of deinduction for various CYP isoforms. To clarify the time courses of deinduction of CYP2C9 and -CYP3A activities after rifampicin withdrawal, we monitored these enzyme activities in 2 patients over time after discontinuing rifampicin. MATERIALS AND METHODS: Two patients (aged 70 and 80 years) received warfarin and rifampicin for anticoagulation and antituberculosis therapy, respectively. Warfarin doses were increased due to rifampicin-induced CYP activity. Upon completion of antituberculosis therapy, rifampicin was discontinued and warfarin doses were titrated downward according to prothrombin time. We monitored CYP2C9 and CYP3A activities over their clinical courses by measuring the metabolic clearance of S-warfarin to S-7-hydroxywarfarin and that of cortisol to 6ß-hydroxycortisol, respectively. RESULTS: In both patients, the time courses of CYP2C9 deinduction appeared to be delayed compared to CYP3A. CONCLUSION: Our findings suggest that a uniform dose reduction protocol for drugs metabolized by different CYP isoforms may be unsafe after rifampicin withdrawal.
.

Evaluation of the impact of cantharidin on rat CYP enzymes by using a cocktail of probe drugs.

The aim of this study was to assess the influence of cantharidin on the activities of the drug-metabolizing enzymes CYP1A2, CYP2C9, CYP2C19, CYP2D6 and CYP3A4 in rats. The activities of CYP1A2, CYP2C9, CYP2C19, CYP2D6 and CYP3A4 were measured using specific probe drugs. After pretreatment for 1week with cantharidin or physiological saline (control group) by intraperitoneal injection, probe drugs phenacetin (5.0mg/kg; CYP1A2 activity), tolbutamide (1.0mg/kg; CYP2C9 activity), omeprazole (10mg/kg; CYP2C19 activity), metoprolol (20mg/kg; CYP2D6 activity) and midazolam (10mg/kg; CYP3A4 activity) were administered to rats by oral administration. The blood was then collected at different times for ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) analysis. The data showed that cantharidin exhibits an inhibitory effect on CYP2D6 and CYP3A4 by increasing t1/2, Cmax and AUC(0-∞), and decreasing CL/F compared with those of the control group. In addition, cantharidin has induction effect on CYP2C9 activity. However, no significant changes in CYP1A2 and CYP2C19 activities were observed. In conclusion, the results indicated that cantharidin could inhibit CYP2D6 and CYP3A4, while induce CYP2C9, which may affect the disposition of medicines primarily dependent on these pathways. Our work may be the basis of related herb-drug interactions in the clinic.

Potentially Unsafe Herb-drug Interactions Between a Commercial Product of Noni Juice and Phenytoin- A Case Report.

PURPOSE: To report the unsafe herb-drug interactions between a commercial product of noni juice and phenytoin in a human case. CASE REPORT: A 49-year-old-male has been treated with phenytoin for epilepsy for more than ten years. In spite of his medication adherence, persistent sub-therapeutic phenytoin levels, which were sometimes from low to undetectable, with the result of having poor seizure control were noted as the noni fruit juice was co-administered daily. The possible mechanism is speculated to be due to noni juiceinduced cytochrome P-450 2C9 metabolism of phenytoin. Owing to many beneficial effects of noni juice, the patient was unwilling to accept our advice to quit taking it. Clobazam treatment was added, and with gradually reducing the amount of juice drunk over six months, the patient's epilepsy has been well controlled. Now only auras along with sometimes minor partial seizures occur, but no major attack has been reported for more than one year. CONCLUSION: Phenytoin had been commonly used for seizure control worldwide and nearly half of patients with epilepsy had received complementary and alternative medicine in Taiwan. Thus, this report is significantly important for clinicians to be aware of the interaction between antiepileptic drugs and some herbs like noni juice. Moreover, as far as we know, this is a rare human case that is reported to disclose this unfavorable herb-drug interaction.

[EVALUATION OF THE PHARMACOKINETIC INTERACTION OF AFOBAZOLE WITH CYP2C9 ENZYME DRUG SUBSTRATE OF CYTOCHROME P450].

We have studied the pharmacokinetics of drug-marker of cytochrome P450 isoenzyme CYP2C9 (losartan) and its metabolite E-3174 after subchronic oral administration of afobazole in doses 5 and 25 mg/kg in rats. The metabolic ratio (MR) of E-3174/Losartan was calculated. The pharmacokinetic parameters of losartan and its metabolite on the background of 4-day afabazole administration 5 mg/kg dose were not significantly different from analogous values calculated for the control group of rats. Therefore, afobazole in the effective anxiolytic dose did not change the MR value of metabolized P450 isoform. A five-fold dose increase in the afobazole dose led to significant difference in pharmacokinetic parameters, including A UC0-t, Cmax, Kel, t1/2el, MRT, CL/F, and Vd/F of losartan and AUC0-T, Cmax, and Tmax of E-3174. These findings are indicative of the induction of CYP2C9 isoenzyme by afobazole.

Case report: dose adjustment of warfarin using genetic information and plasma concentration monitoring.

WHAT IS KNOWN AND OBJECTIVE: Carbamazepine is known to interact with warfarin. We report on a case of this interaction and on its management using the patient's genetic information. CASE SUMMARY: The case concerns a 74-year-old Japanese woman with a mood disorder and a central retinal vein occlusion. She was on therapy that included carbamazepine and had started to take warfarin. However, the patient's prothrombin time expressed as the international normalized ratio (PT-INR) was 1·40 despite taking a dose three times higher than the average. The patient's S-warfarin concentration was 0·15 µg/mL and R-warfarin was 0·52 µg/mL. Her cytochrome P450 2C9 (CYP2C9) and vitamin K epoxide reductase complex, subunit 1 (VKORC1), genotypes were *1/*1 and -1639GA, respectively. The VKORC1 genotype indicated that she would require an even higher dose. We proposed a further increase in dose and the patient's PT-INR rose to 1·99. WHAT IS NEW AND CONCLUSION: The patient required a high warfarin dose because of the VKORC1 genotype, and induction of CYP2C9 by carbamazepine. We improved the patient's pharmacotherapy based on her genetic information.