Effect of CYP2D6 polymorphisms on the pharmacokinetics of propafenone and its two main metabolites

The Effect of CYP2D6 Phenotypes on the Pharmacokinetics of Propafenone: A Systematic Review and Meta-Analysis

Propafenone (PPF) is a class 1C antiarrhythmic agent mainly metabolized by cytochrome (CYP) 2D6, CYP1A2, and CYP3A4. Previous studies have shown that CYP2D6 polymorphism influences the pharmacokinetics (PK) of PPF. However, the small sample sizes of PK studies can lead to less precise estimates of the PK parameters. Thus, this meta-analysis was performed to merge all current PK studies of PPF to determine the effects of the CYP2D6 phenotype more accurately on the PPF PK profile. We searched electronic databases for published studies to investigate the association between the PPF PK and CYP2D6 phenotype. Four PK-related outcomes were included: area under the time–concentration curve (AUC), maximum concentration (Cmax), apparent clearance (CL/F), and half-life (t1/2). A total of five studies were included in this meta-analysis (n = 56). Analyses were performed to compare PK parameters between poor metabolizers (PMs) versus extensive metabolizers (EMs). PPF has a non-linear pharmacokinetics; therefore, analyses were performed according to dose (300 mg and 400 mg). At 300 mg, the AUC mean (95% CI), Cmax, and t1/2 of PPF in PMs were 15.9 (12.5–19.2) µg·h/mL, 1.10 (0.796–1.40) µg/mL, and 12.8 (11.3–14.3) h, respectively; these values were 2.4-, 11.2-, and 4.7-fold higher than those in the EM group, respectively. At 400 mg, a comparison was performed between S- and R-enantiomers. The CL/F was approximately 1.4-fold higher for the R-form compared with the S-form, which was a significant difference. This study demonstrated that CYP2D6 metabolizer status could significantly affect the PPF PK profile. Adjusting the dose of PPF according to CYP2D6 phenotype would help to avoid adverse effects and ensure treatment efficacy.

Influence of CYP2D6 Genetic Variation on Adverse Events with Propafenone in the Pediatric and Young Adult Population

Propafenone is an antiarrhythmic drug metabolized primarily by cytochrome P450 2D6 (CYP2D6). In adults, propafenone adverse events (AEs) are associated with CYP2D6 poor metabolizer status; however, pediatric data are lacking. Subjects were tested for 10 CYP2D6 allelic variants and copy number status, and activity scores assigned to each genotype. Seventy‐six individuals (median 0.3 [range 0–26] years old) were included. Propafenone AEs occurred in 29 (38%); 14 (18%) required drug discontinuation due to AE. The most common AEs were QRS (n = 10) and QTc (n = 6) prolongation. Those with AEs were older at the time of propafenone initiation (1.58 [0.13–9.92] vs. 0.20 [0.08–2.01] years old; p = 0.042). CYP2D6 activity scores were not associated with presence of an AE (odds ratio [OR] 0.48 [0.22–1.03]; p = 0.055) but with the total number of AE (β₁ = −0.31 [−0.60, −0.03]; p = 0.029), systemic AEs (OR 0.33 [0.13–0.88]; p = 0.022), and drug discontinuation for systemic AEs (OR 0.28 [0.09–0.83]; p = 0.017). Awareness of CYP2D6 activity score and patient age may aid in determining an individual's risk for an AE with propafenone administration.

Sex, estrous cycle, and hormone regulation of CYP2D in the brain alters oxycodone metabolism and analgesia

Opioids, and numerous centrally active drugs, are metabolized by cytochrome P450 2D (CYP2D). There are sex and estrous cycle differences in brain oxycodone analgesia. Here we investigated the mechanism examining the selective role of CYP2D in the brain on sex, estrous cycle, and hormonal regulation. Propranolol, CYP2D-specific mechanism-based inhibitor, or vehicle was delivered into cerebral ventricles 24 hours before administering oxycodone (or oxymorphone, negative control) orally to male and female (in estrus and diestrus) rats. Ovariectomized and sham-operated females received no treatment, estradiol, progesterone or vehicle. Analgesia was measured using tail-flick latency, and brain drug and metabolite concentrations were measured by microdialysis. Data were analyzed by two-way or mixed ANOVA. Following propranolol (versus vehicle) inhibition and oral oxycodone, there were greater increases in brain oxycodone concentrations and analgesia, and greater decreases in brain oxymorphone/oxycodone ratios (an in vivo phenotype of CYP2D in brain) in males and females in estrus, compared to females in diestrus; with no impact on plasma drug concentrations. There was no impact of propranolol pre-treatment, sex, or cycle after oral oxymorphone (non-CYP2D substrate) on brain oxymorphone concentrations or analgesia. There was no impact of propranolol pre-treatment following ovariectomy on brain oxycodone concentrations or analgesia, which was restored in ovariectomized females following estradiol, but not progesterone, treatment. Sex, cycle, and estradiol regulation of CYP2D in brain in turn altered brain oxycodone concentration and response, which may contribute to the large inter-individual variation in response to the numerous centrally acting CYP2D substrate drugs, including opioids.

Pharmacogenetics to guide cardiovascular drug therapy

Over the past decade, pharmacogenetic testing has emerged in clinical practice to guide selected cardiovascular therapies. The most common implementation in practice is CYP2C19 genotyping to predict clopidogrel response and assist in selecting antiplatelet therapy after percutaneous coronary intervention. Additional examples include genotyping to guide warfarin dosing and statin prescribing. Increasing evidence exists on outcomes with genotype-guided cardiovascular therapies from multiple randomized controlled trials and observational studies. Pharmacogenetic evidence is accumulating for additional cardiovascular medications. However, data for many of these medications are not yet sufficient to support the use of genotyping for drug prescribing. Ultimately, pharmacogenetics might provide a means to individualize drug regimens for complex diseases such as heart failure, in which the treatment armamentarium includes a growing list of medications shown to reduce morbidity and mortality. However, sophisticated analytical approaches are likely to be necessary to dissect the genetic underpinnings of responses to drug combinations. In this Review, we examine the evidence supporting pharmacogenetic testing in cardiovascular medicine, including that available from several clinical trials. In addition, we describe guidelines that support the use of cardiovascular pharmacogenetics, provide examples of clinical implementation of genotype-guided cardiovascular therapies and discuss opportunities for future growth of the field.

Effect of CYP2D6 genetic polymorphism on peak propafenone concentration: no significant effect of CYP2D6*10

Aim: The study aims to investigate the clinical implication of nonfunctional poor metabolizer (PM) alleles and intermediate metabolizer (IM) alleles of CYP2D6, including the CYP2D6*10 allele which shows substrate-dependent decrease in enzymatic activity, in antiarrhythmic therapy using propafenone. Materials & methods: We examined serum propafenone concentrations and metabolic ratio, which was expressed as serum concentrations of propafenone to 5-hydroxypropafenone, in 66 Japanese patients with tachyarrhythmias. Results: The peak propafenone concentration and metabolic ratio in CYP2D6 PM allele carriers were higher than those in extensive metabolizer (EM)/EM, EM/IM and IM/IM genotype groups. Conclusion: Results suggest that CYP2D6 PM alleles affect peak propafenone concentration, but the CYP2D6 IM allele CYP2D6*10 has no clinical implication in propafenone dosing.

Pharmacogenomics of Medications Commonly Used in the Intensive Care Unit

In the intensive care unit (ICU) setting, where highly variable and insufficient drug efficacies, as well as frequent and unpredictable adverse drug reactions (ADRs) occur, pharmacogenomics (PGx) offers an opportunity to improve health outcomes. However, PGx has not been fully evaluated in the ICU, partly due to lack of knowledge of how genetic markers may affect drug therapy. To fill in this gap, we conducted a review to summarize the PGx information for the medications commonly encountered in the ICU.

Practical management of ibrutinib in the real life: Focus on atrial fibrillation and bleeding

The Bruton tyrosine kinase inhibitor ibrutinib (IB) has attained an important role in the treatment of patients with chronic lymphocytic leukaemia, mantle cell lymphoma, and Waldenström macroglobulinemia, significantly improving clinical outcomes. However, IB therapy has been associated with an increased risk of atrial fibrillation (AF) and bleeding. We report on the expert opinion that a group of Italian haematologists, cardiologists, and pharmacologists jointly released to improve the practical management of patients at risk for AF and bleeding during treatment with IB. A proper pretreatment assessment to identify patients who are at a higher risk, careful choice of concomitant drugs, regular monitoring, and multispecialist approach were characterized as the main principles of clinical management of these patients. For patients developing AF, anticoagulant and antiarrhythmic therapy must be guided by considerations about efficacy, safety, and risk of pharmacokinetic interactions with IB. For patients experiencing bleeding or requiring procedures that increase the risk of bleeding, considerations about platelet turnover, IB-related platelet dysfunctions, and bleeding worsening by concomitant anticoagulants or antiplatelet agents provide clues to manage bleeding. Overall, AF and bleeding are manageable clinical events in patients receiving IB, not requiring drug interruption in most cases. Preexisting AF should not represent an absolute contraindication to IB therapy. For each patient candidate for IB, strategies of risk assessment and mitigation may allow to exploit the life-saving effects of in chronic lymphocytic leukaemia and mantle cell lymphoma.