Predictive value of known and novel alleles ofCYP2B6 for efavirenz plasma concentrations in HIV-infected individuals

© 2008 American Society for Clinical Pharmacology and TherapeuticsTo assess the association of CYP2B6 allelic diversity with efavirenz (EFV) pharmacokinetics, we performed extensive genotyping of 15 relevant single nucleotide polymorphism in 169 study participants, and full resequencing of CYP2B6 in individuals with abnormal EFV plasma levels. Seventy-seven (45.5%) individuals carried a known (CYP2B66,11,15, or 18) or new loss/diminished-function alleles. Resequencing defined two new loss-of-function alleles: allele 27 (marked by 593T>C [M198T]), that results in 85% decrease in enzyme activity and allele 28 (marked by 1132C>T), that results in protein truncation at arginine 378. Median AUC levels were 188.5 g h/ml for individuals homozygous for a loss/diminished-function allele, 58.6 g h/ml for carriers, and 43.7 g h/ml for noncarriers (P<0.0001). Individuals with a poor metabolizer genotype had a likelihood ratio of 35 (95% CI, 11–110) of presenting very high EFV plasma levels. CYP2B6 poor metabolizer genotypes explain to a large extent EFV pharmacokinetics and identify individuals at risk of extremely elevated EFV plasma levels

Selective induction of human hepatic cytochromes P450 2B6 and 3A4 by metamizole

The pyrazolone drug metamizole is a widely used analgesic. Analysis of liver microsomes from patients treated with metamizole revealed selectively higher expression of cytochromes P450, CYP2B6 and CYP3A4 (3.8- and 2.8-fold, respectively), and 2.9-fold higher bupropion hydroxylase activity compared with untreated subjects. Further investigation of metamizole and various derivatives on different potential target genes in human primary hepatocytes demonstrated time- and concentration-dependent induction by metamizole of CYP2B6 (7.8- and 3.1-fold for mRNA and protein, respectively, at 100 M) and CYP3A4 (2.4- and 2.9-fold, respectively), whereas other genes (CYP2C9, CYP2C19, CYP2D6, NADPH:cytochrome P450 reductase, ABCB1, constitutive androstane receptor (CAR), pregnane X receptor (PXR)) were not substantially altered. Using reporter gene assays, we show that metamizole is not acting as a direct ligand to either PXR or CAR, suggesting a phenobarbital-like mechanism of induction. These data warrant further studies to elucidate the drug-interaction potential of metamizole, especially in patients with long-term treatment.T Saussele, O Burk, J K Blievernicht, K Klein, A Nussler, N Nussler, J G Hengstler, M Eichelbaum, M Schwab, and U M Zange

Initiation of sacubitril/valsartan in haemodynamically stabilised heart failure patients in hospital or early after discharge: primary results of the randomised TRANSITION study

Aims: To assess tolerability and optimal time point for initiation of sacubitril/valsartan in patients stabilised after acute heart failure (AHF). Methods and results: TRANSITION was a randomised, multicentre, open-label study comparing two treatment initiation modalities of sacubitril/valsartan. Patients aged ≥ 18 years, hospitalised for AHF were stratified according to pre-admission use of renin–angiotensin–aldosterone system inhibitors and randomised (n = 1002) after stabilisation to initiate sacubitril/valsartan either ≥ 12-h pre-discharge or between Days 1–14 post-discharge. Starting dose (as per label) was 24/26 mg or 49/51 mg bid with up- or down-titration based on tolerability. The primary endpoint was the proportion of patients attaining 97/103 mg bid target dose after 10 weeks. Median time of first dose of sacubitril/valsartan from. the day of discharge was Day –1 and Day +1 in the pre-discharge group and the post-discharge group, respectively. Comparable proportions of patients in the pre- and post-discharge initiation groups met the primary endpoint [45.4% vs. 50.7%; risk ratio (RR) 0.90; 95% confidence interval (CI) 0.79–1.02]. The proportion of patients who achieved and maintained for ≥ 2 weeks leading to Week 10, either 49/51 or 97/103 mg bid was 62.1% vs. 68.5% (RR 0.91; 95% CI 0.83–0.99); or any dose was 86.0% vs. 89.6% (RR 0.96; 95% CI 0.92–1.01). Discontinuation due to adverse events occurred in 7.3% vs. 4.9% of patients (RR 1.49; 95% CI 0.90–2.46). Conclusions: Initiation of sacubitril/valsartan in a wide range of heart failure with reduced ejection fraction patients stabilised after an AHF event, either in hospital or shortly after discharge, is feasible with about half of the patients achieving target dose within 10 weeks. Clinical Trial Registration: ClinicalTrials.gov ID: NCT02661217. © 2019 The Authors. European Journal of Heart Failure published by John Wiley & Sons Ltd on behalf of European Society of Cardiology