[Effect of genetic polymorphism of cytochrome P450 3A and transporter gene on pharmacokinetics of tacrolimus, a calcineurin inhibitor]

[Clinical Impact of Vonoprazan on the Use of Midazolam during Upper Gastrointestinal Endoscopy]

Despite that the Japanese package insert for vonoprazan (VPZ) includes a precaution that the potassium ion-competitive acid blocker may potentiate the effects of midazolam (MDZ), reports on the actual effects in clinical practice are lacking. Therefore, in this study, we evaluated whether VPZ-taking patients experience clinical effects under MDZ sedation during endoscopy. The participants were outpatients who underwent upper gastrointestinal endoscopy under MDZ anesthesia between April 2021 and April 2022. Comparisons were made between the VPZ(+) and VPZ(-) groups, and the patient background was adjusted using propensity score matching. The post-examination observation time was prolonged in 16.4% of patients in the VPZ(+) group and 13.7% in the VPZ(-) group, but the difference was not statistically significant (p=0.818). The two patients groups also showed no statistically significant differences in the percentage of individuals who received oxygen administration during the examination or in post-examination oxygen saturation and blood pressure values. These results suggest that the use of MDZ for sedation during upper gastrointestinal endoscopy may have minimal clinical effects arising from drug interaction with VPZ.

[Metabolic Activities Catalyzed by Human Cytochrome P450 (CYP) 2D6 and CYP3A Subfamily Members and Effect of Various Compounds, Including Endogenous Steroid Hormones, on These Activities]

My research focused on the effects of various drugs on (1) dopamine formation from p-tyramine catalyzed by polymorphic cytochrome P450 (CYP or P450) 2D6 variants and (2) endogenous steroid hormone hydroxylation catalyzed by CYP3A subfamily members (CYP3A4, CYP3A5, CYP3A7). The activation (cooperativity) of metabolic reactions catalyzed by P450s was especially emphasized. The effects of various psychotropic agents on dopamine formation from p-tyramine, catalyzed by wild-type CYP2D6.1 and CYP2D6 variants, including CYP2D6.2 (Arg296Cys;Ser486Thr), CYP2D6.10 (Pro34Ser;Ser486Thr), and CYP2D6.39 (Ser486Thr) were compared. Michaelis (Km) and inhibition (Ki) constants of the psychotropic agents in the presence of CYP2D6.10 were higher than those observed in the presence of other CYP2D6 variants. Fluvoxamine, fluoxetine, milnacipran, and haloperidol activated CYP2D6-catalyzed dopamine formation [decreasing the Km and/or increasing the maximal velocity (kcat)], and this activation was CYP2D6 variant-dependent. Regarding the CYP3A subfamily, the effects of various compounds including endogenous steroid hormones on the 6β-hydroxylation of steroid hormones, such as testosterone, progesterone, and cortisol, were determined; it was found that testosterone, dehydroepiandrosterone, and/or α-naphthoflavone activated 6β-hydroxylation of cortisol and/or progesterone, but the effects varied in the presence of different CYP3A subfamily members. Further studies are required to confirm the mechanisms and therapeutic relevance of these activation phenomena.

The effect of CYP3A5 genetic polymorphisms on adverse events in patients with ulcerative colitis treated with tacrolimus

BACKGROUND

Tacrolimus is an immunosuppressive agent, used in the remission induction therapy of ulcerative colitis (UC).

AIMS

We investigated the correlation between CYP3A5 genetic polymorphisms and the adverse events in patients with UC. The pharmacokinetics of tacrolimus after oral administration were also analyzed.

METHODS

We enrolled 29 hospitalized patients with UC received oral tacrolimus. Genotyping for CYP3A5 A6986G (rs776746) was performed using Custom TaqMan® SNP genotyping assays. Adverse events, concentration and dose (C/D) ratios and clinical outcomes were investigated.

RESULTS

CYP3A5 expressers and non-expressers were 16 and 13, respectively. C/D ratios of CYP3A5 expressers were significantly lower compared to non-expressers. The response rate in CYP3A5 non-expressers was relatively higher in the early phase of treatment compared to expressers, but not statistically significant. The incidence of overall adverse events was significantly higher in CYP3A5 expressers than in non-expressers (P=0.034, chi-squared test). In particular, the incidence of nephrotoxicity was significantly higher in CYP3A5 expressers compared to non-expressers (P=0.027, chi-squared test). All of the nephrotoxicity were reversible and resolved by discontinuation or dose reduction of tacrolimus.

CONCLUSION

The adverse events especially nephrotoxicity were frequently observed in CYP3A5 expressers. CYP3A5 expressers should be paid attention to the onset of nephrotoxicity.

Pharmacokinetics of orally administered tacrolimus in lupus nephritis patients

The pharmacokinetics of orally administered tacrolimus were examined in six female lupus nephritis patients (mean age 43 years, range 24-55 years). Tacrolimus (3 mg) was administered after supper, and blood tacrolimus concentrations were measured just prior to dosing and 1, 2, 4, 6, 8, 12 and 24 h after administration. The maximum blood concentration (C(max)) was observed 4-8 h (mean: 6.7 h) after administration. The mean C(max) and area under the tacrolimus concentrationti-me curve (AUC(0-24 h)) were 12.7 ng/ml and 163.1 ng x h/ml, respectively. Although there was a weak correlation between AUC(0-24 h) values and tacrolimus concentrations 2, 4, and 6 h after administration, concentrations at 12 h and 24 h were highly correlated with AUC(0-24 h) values, suggesting that the trough concentration (C(24 h)) and C(12 h) are valid markers for therapeutic tacrolimus monitoring. Enzyme-linked immunoabsorbent assay (ELISA) and microparticle enzyme immunoassay (MEIA) measurements of blood tacrolimus concentrations were similar. We recommend that monitoring should be carried out by C(12 h) in lupus nephritis outpatients.