Effect of Amiodarone on the Serum Concentration/Dose Ratio of Metoprolol in Patients with Cardiac Arrhythmia

Impact of amiodarone use on metoprolol concentrations, α-OH-metoprolol concentrations, metoprolol dosing and heart rate: A cross-sectional study

Small studies suggest that amiodarone is a weak inhibitor of cytochrome P450 (CYP) 2D6. Inhibition of CYP2D6 leads to increases in concentrations of drugs metabolized by the enzyme, such as metoprolol. Considering that both metoprolol and amiodarone have β-adrenergic blocking properties and that the modest interaction between the two drugs would result in increased metoprolol concentrations, this could lead to a higher risk of bradycardia and atrioventricular block. The primary objective of this study was to evaluate whether metoprolol plasma concentrations collected at random timepoints from patients enrolled in the Montreal Heart Institute Hospital Cohort could be useful in identifying the modest pharmacokinetic interaction between amiodarone and metoprolol. We performed an analysis of a cross-sectional study, conducted as part of the Montreal Heart Institute Hospital Cohort. All participants were self-described "White" adults with metoprolol being a part of their daily pharmacotherapy regimen. Of the 999 patients being treated with metoprolol, 36 were also taking amiodarone. Amiodarone use was associated with higher metoprolol concentrations following adjustment for different covariates (p = .0132). Consistently, the association between amiodarone use and lower heart rate was apparent and significant after adjustment for all covariates under study (p = .0001). Our results highlight that single randomly collected blood samples can be leveraged to detect modest pharmacokinetic interactions.

Loss of Coordinated Neutrophil Responses to the Human Fungal Pathogen, Candida albicans, in Patients With Cirrhosis

Neutrophils are the most abundant white blood cell in the body and are key participants in the defense against fungal infections. Fungal infections occur often in patients with cirrhosis and are associated with increased 30-day and 90-day mortality. Previous studies have shown that specific neutrophil functions are abnormal in patients with cirrhosis, although the extent of neutrophil dysfunction is not well understood. We tested the ability of neutrophils from 21 hospitalized patients with cirrhosis and 23 healthy control patients to kill Candida albicans, a common fungal pathogen in patients with cirrhosis. Using an assay, we also measured the ability of neutrophils to coordinate multicellular, synchronized control of C. albicans hyphae through a process known as swarming. We found that neutrophils from patients with cirrhosis have significantly decreased fungicidal capacity compared with healthy control neutrophils (53% vs. 74%, P < 0.0001) and diminished ability to control hyphal growth normalized as a ratio to healthy control (0.22 vs. 0.65, P < 0.0001). Moreover, serum from patients with cirrhosis decreases the ability of healthy control neutrophils to kill C. albicans (from 60% to 41%, P < 0.003). Circulating concentration of the inflammatory cytokines tumor necrosis factor α, interleukin-6, and interleukin-8 were found to be significantly elevated in patients with cirrhosis compared to healthy controls. Following pretreatment with granulocyte-colony stimulating factor and granulocyte-macrophage colony-stimulating factor, neutrophil function was restored to almost that of healthy controls. Conclusion: Our data establish profound neutrophil dysfunction against, and altered swarming to, C. albicans in patients with cirrhosis. This dysfunction can be partially reversed with cytokine augmentation ex vivo.

Low-dose Amiodarone Is Safe: A Systematic Review and Meta-analysis

Amiodarone is commonly used for a variety of arrhythmias and, in some parts of the world, is the only available antiarrhythmic drug (AAD). Yet, amiodarone is known to have a wide range of potential side effects, many of which are dose- and duration-dependent. We sought to study the incidence of side effects leading to the discontinuation of low-dose amiodarone, arbitrarily defined as 200 mg/day or less, and very-low-dose amiodarone, defined as 100 mg/day or less. In this study, literature databases were searched through June 2019. Studies that reported the incidence or prevalence of side effects of amiodarone were included. Effect estimates from individual studies were extracted and combined using the random-effects generic inverse variance method of DerSimonian and Laird. A total of 10 observational cohort studies involving 901 patients were included in the analysis. The pooled estimated incidence of overall side effects for low-dose amiodarone was 0.17 [95% confidence interval (CI): 0.12–0.22]. In addition, the pooled estimated incidence of side effects requiring medication discontinuation was 0.06 (95% CI: 0.03–0.11). As compared with 200 mg/day of amiodarone, the pooled estimated incidence of overall side effects was 0.11 (95% CI: 0.04–0.27), while the incidence of side effects requiring medication discontinuation was 0.02 (95% CI: 0.01–0.06) for the dose of 100 mg/day. In conclusion, very-low-dose amiodarone displays a low incidence of significant side effects requiring medication discontinuation.

Medication-related problems encountered in the Program of All-Inclusive Care for the Elderly: An observational study

OBJECTIVE

To evaluate pharmacist-encountered medication-related problems (MRPs) among the participants of the Program of All-Inclusive Care for the Elderly (PACE).

DESIGN

This was a retrospective analysis of proprietary pharmacy records detailing pharmacist encounters with PACE clinical staff.

SETTING AND PARTICIPANTS

A national provider of pharmacy services to more than 75 PACE organizations. In total, 1057 PACE participants at 69 PACE sites across the United States with documented pharmacist encounters between March and May 2018.

OUTCOME MEASURES

MRPs were classified using the Hepler-Strand taxonomy, and pharmacists' recommendations made to prescribers to resolve these MRPs were classified using a modified Hoth taxonomy. In addition, pharmacists' communication methods and prescribers' responses were analyzed.

RESULTS

Overall, 2004 MRPs were encountered. The most frequent MRPs identified were related to medication safety concerns, including drug interactions (720, 35.9%), adverse drug reactions (ADRs, 356, 17.8%), high doses (270, 13.5%), and unindicated drugs (252, 12.6%). Drug interactions frequently involved competitive inhibition, 3 or more drugs, opioids, anticoagulants, antiplatelets, and antidepressants. Deprescribe medication (561, 24.8%), start alternative therapy (553, 24.4%), change doses (457, 20.2%), and monitor (243, 10.7%) were the top 4 types of recommendations made by pharmacists. Among 1730 responses obtained from PACE prescribers, 78.1% (n = 1351) of pharmacists' recommendations were accepted. Compared with electronic communication, telephonic communication was associated with more acceptance and less prescriber nonresponse (χ² = 78.5, P < 0.001).

CONCLUSION

Pharmacists identified a substantial number of MRPs in PACE, especially those related to medication safety such as drug interactions and ADRs. In this practice setting, significant collaboration occured between pharmacists and PACE prescribers, as evidenced by the rate of prescribers' acceptance of pharmacists' recommendations. Further research is needed to fully evaluate the economic, clinical, and humanistic outcomes associated with pharmacists' encounters in PACE.

Drug-Drug Interactions Of Amiodarone And Quinidine On The Pharmacokinetics Of Eliglustat In Rats

Background

Eliglustat, a new oral substrate-reduction therapy, was recently approved as a first-line therapy for Gaucher's disease type 1 (GD1) patients.

Purpose

The purpose of the present study was to develop and validate a simple UPLC-MS/MS method for the measurement of plasma-eliglustat concentration and to investigate the effects of amiodarone and quinidine on eliglustat metabolism in rats.

Methods

Eighteen rats were randomly divided into three groups (n=6): control (0.5% CMC-Na, group A), amiodarone (60 mg/kg, group B), and quinidine (100 mg/kg, group C). Thirty minutes later, 10 mg/kg eliglustat was orally administered to each rat and concentrations of eliglustat in the rats determined by our UPLC-MS/MS method.

Results

Amiodarone and quinidine increased the main pharmacokinetic parameters (AUC0→_t, AUC_0→∞, and C_max) of eliglustat significantly and decreased clearance obviously.

Conclusion

Amiodarone and quinidine can elevate eliglustat exposure and have an inhibitory effect on eliglustat metabolism. Clearly, appropriate pharmacological studies of eliglustat in patients treated with amiodarone or quinidine should be done in future.

[Clinical aspects of treatment with amiodarone]

Amiodarone has multiple and complex electrophysiological effects that render it a very effective antiarrhythmic drug for the treatment of both, supraventricular and ventricular arrhythmias. Proarrhythmic effects of amiodarone in patients with structural heart disease are rare. However, extracardiac adverse effects occurring in association with amiodarone treatment are frequent and feared. These adverse effects have usually been related to total amiodarone exposure (i. e., dose and duration of treatment). Parallel to a more frequent use of lower amiodarone maintenance doses (100-200 mg/day), the incidence of severe unwanted extracardiac side effects has decreased. High-dose maintenance regiments (daily dose ≥300 mg) are usually obsolete. This paper discusses recommendations regarding the monitoring of cardiac and extracardiac side effects of amiodarone. They need to be regarded by physicians using amiodarone to ensure long-term safety of amiodarone therapy.

Therapeutic monitoring of amiodarone: pharmacokinetics and evaluation of the relationship between effect and dose/concentration

Amiodarone is the most effective agent in the therapy of arrhythmias. However, the clinical effect of acute and chronic treatment is unclear and there are differences irrespective of comparable plasma/myocardial amiodarone and its metabolite desethylamiodarone concentations as well. Its unusual pharmacokinetics results in interindividual variation in plasma levels. The association between amiodarone and desethylamiodarone plasma levels and clinical efficacy is difficult to evaluate. This review was carried out to assess whether there is any objective correlation between amiodarone and desethylamiodarone plasma levels and the clinical effect. We summarized the results of relevant studies and clarified the relationship between plasma levels and effect vis á vis the pharmacokinetics and pharmacogenetics of this drug. Certain correlation was seen with oral amiodarone therapy, in others, plasma amiodarone levels were unrelated to therapeutic response and showed no correlation with changes in electrocardiogram or electrophysiological parametres. Several studies show that plasma concentration ranging between 0.5 and 2.5 mg/L appears to be the most effective, others demonstrate no difference between responders and non-responders. One way of interpreting plasma levels is to establish an individual patient´s effective concentration. Therapeutic drug monitoring can contribute to determining optimal concentration.

Lotus leaf alkaloid fraction can strongly inhibit CYP2D6 isoenzyme activity

ETHNOPHARMACOLOGICAL RELEVANCE

The Chinese herbal medicine He-Ye, the leaves of the lotus (Nelumbo nucifera) plant, is traditionally used in China for the treatment of sunstroke, thirst, diarrhea, and fever. Currently, the leaf is used not only as an herbal tea to reduce lipid level and control body weight, but also as a major ingredient in some lipid-lowering Chinese patented medicines. Our previous study demonstrated that the alkaloid fraction (AF) of the herb has a strong inhibitory effect on CYP2D6 isoenzyme activity in vitro. The present study aims to further verify this activity using the in vivo rat model and to explore the inhibitory mechanism on CYP2D6 using human liver microsomes (HLMs).

MATERIALS AND METHODS

After a continuous 7-d oral dose of AF (50mg/kg) or a vehicle, Sprague Dawley rats received a single intravenous dose of dextromethorphan or metoprolol. Blood samples were collected at various time points, and the plasma concentrations of the relevant metabolites dextrorphan and hydroxymetoprolol were assayed by LC-MS/MS for evaluating the effect of AF on their pharmacokinetics and CYP2D6 activity. Dextromethorphan as a probe at different concentrations was incubated with HLMs in an incubation buffer system, in the presence or absence of AF at different concentrations. After incubation, the produced metabolite was assayed.

RESULTS

After being pretreated with AF in rats, the plasma concentrations of dextrorphan and hydroxymetoprolol significantly decreased, with C_max going from 79.44 to 29.96 and 151.18 to 83.39hng/mL (P<0.05), AUC_all from 167.27 to 62.25 and 347.68 to 223.24hng/mL (P<0.05), and AUC_inf from 183.39 to 84.76 and 350.59 to 234.57hng/mL (P<0.05), respectively, in comparison with those of untreated rats. The t_1/2 of hydroxymetoprolol significantly increased from 1.14 to 1.99h (P<0.05). The in vitro incubation test showed that AF competitively inhibited the CYP2D6, with apparent K_i value of 0.64µg/mL.

CONCLUSIONS

AF can strongly inhibit the activity of CYP2D6 enzyme, as confirmed by in vivo and in vitro models. Possible drug interactions may occur between AF and other medications metabolized by CYP2D6. Thus, caution should be paid when the lotus leaf and its preparations are concurrently administered with conventional medicines.

Natural products-friends or foes?

A trend in the general population has been observed in recent years regarding the orientation toward preventive measures in health; in this context the increased interest from the users and researchers concerning the active effect of food supplements on the health state and on longevity, is noticeable. All over the world, the consumption of natural foods and of vegetal supplements has increased spectacularly over the last 5-10 years. The decreased prevalence of cardio-vascular diseases associated with Mediterranean diet, as well as the French paradox convinced researchers to scientifically document the beneficial outcomes pointed out by traditional use of plants, and to try to develop supplements that would have the same positive effects as these noticed for diet components. The intense research dedicated to this topic revealed the fact that food supplements are linked to some problematic aspects, such as toxicological side effects when associated with classical synthetic drugs. The food supplement-drug interactions are submitted to complex issues regarding pharmacokinetic interactions leading to changes in absorption, distribution, metabolism and excretion processes with direct impact on effect and toxicological potential. The present review based on recent literature aims at discussing the food-drug interactions with direct impact on efficacy and toxicity of drugs.

Inhibitory mechanisms of celastrol on human liver cytochrome P450 1A2, 2C19, 2D6, 2E1 and 3A4

1. The present study was conducted to examine the possibility of herb-drug interaction by celastrol, which is a main compound isolated from Tripterygium wilfordii Hook F. using human liver microsomes with cocktail methods. Focused on its inhibitory manner on the metabolism of model probe substrates of five cytochrome P450 isoenzymes (CYP1A2, CYP2C19, CYP2D6, CYP2E1 and CYP3A4) in vitro which are important with the metabolism of different xenobiotics. 2. The results showed that celastrol inhibited the five types of human cytochrome P450 isoforms, with the IC50 values of 2.65 μM (CYP3A4), 5.99 μM (CYP2C19), 6.27 μM (CYP2D6), 7.66 μM (CYP1A2) and 9.38 μM (CYP2E1), respectively. The data indicated that celastrol acted in different manners as an inhibitor of human cytochrome P450 isoforms, which showed that celastrol not only un-competitively inhibited the CYP1A2 and 2E1 activities, but also competitively inhibited the CYP2C19 and 2D6 activities with Ki values of 1.41, 2.29, 5.27 and 4.21 μM, respectively. Celastrol was also a mixed-type inhibitor of CYP3A4, with Ki and Kis values of 2.02 and 5.49 μM, respectively. 3. Celastrol has the potential to inhibit cytochrome P450 activities and may cause the herb-drug interactions. Therefore, the use of celastrol and its preparations with conventional medicines should thus be taken in to account.

Identification and characterization of potent CYP2D6 inhibitors in lotus leaves

ETHNOPHARMACOLOGICAL RELEVANCE

The herb of lotus (Nelumbo nucifera) leaves is a commonly used traditional Chinese herbal medicine that is utilized for the treatment of sunstroke, to assuage thirst, and to cure both diarrhea and fever in China. Modern pharmacological studies have demonstrated that the herb exhibits various pharmacological effects, such as anti-hyperlipidemia, anti-obesity, anti-oxidant, anti-HIV, anti-microbial, and anti-hypoglycemic activities. Currently, the herb is becoming more popular in China as a "tea drink" or as a main ingredient of some herbal formulations, which implies that the herb and/or its products are now more likely to be concurrently administered with conventional medicines for losing body weight and reducing blood lipids. However, its potential inhibitory effect on human cytochrome P450 (CYP) has not been systemically investigated to date. The present study was performed to assess the potential inhibitory effects of lotus leaf alcoholic extract (LAE), its major fractions, and its main compounds on five CYP isoenzymes (CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A4) in vitro.

MATERIAL AND METHODS

Five probe substrates were incubated with human liver microsomes in the presence or absence of the LAE, the alkaloid fraction (AF), the flavonoid fraction (FF), or the individual aporphine alkaloids, namely, nuciferine (NF), N-nornuciferine (N-NF), and 2-hydroxy-1-methoxyaporphine (HMA). After the incubation, the relative metabolites of the substrates were analyzed using LC-MS/MS.

RESULTS

The results showed that the LAE strongly inhibited CYP2D6 with an IC50 value of 12.05µg/mL and weakly inhibited other isoenzymes. In addition, FF was found to weakly inhibit CYP2D6, whereas AF exerted a markedly higher inhibitory effect on CYP2D6 activity with an IC50 value of 0.96µg/mL. The three aporphine alkaloids isolated from the AF (NF, N-NF, and HMA) significantly inhibited CYP2D6 with IC50 values of 3.78, 3.76, and 3.15µM, respectively. Their Lineweaver-Burk plots and Dixon plots showed that NF, N-NF, and HMA competitively inhibited CYP2D6 activity with Ki values of 1.88, 2.34, and 1.56µM, respectively.

CONCLUSION

The study revealed that the alkaloid compounds in lotus leaves exert a potent inhibitory effect on CYP2D6 isoenzyme. The possible drug interactions of the leaves and their preparations with conventional medicines should thus be taken into account.

Cytochrome P450-mediated cardiovascular drug interactions

INTRODUCTION

There are numerous drug-drug interactions (DDIs) related to cardiovascular medications and many of these are mediated via the cytochrome P450 (CYP) system. Some of these may lead to serious adverse events and it is, therefore, essential that clinicians are aware of the important interactions that occur.

AREAS COVERED

An extensive literature search was performed to analyze the CYP-mediated cardiovascular DDIs that lead to a loss of efficacy or potential toxicity. Cardiovascular drugs may be victims or act as perpetrators of DDIs. The paper analyzes CYP-mediated drug interactions concerning anticoagulants, antiplatelet agents, antiarrhythmics, β-blockers, calcium antagonists, antihypertensive medications, lipid-lowering drugs and oral antidiabetic agents.

EXPERT OPINION

Cardiovascular DDIs involving the CYP system are numerous. Additionally, the spectrum of drugs prescribed is constantly changing, particularly with cardiovascular diseases and it is not necessarily the case that drugs that had shown safety earlier will always show safety. Clinicians are encouraged to develop their knowledge of CYP-mediated DDIs so that they can choose safe drug combination regimens, adjust drug dosages appropriately and conduct therapeutic drug monitoring for drugs with narrow therapeutic indices.

Pharmacogenetics and breast cancer endocrine therapy: CYP2D6 as a predictive factor for tamoxifen metabolism and drug response?

The identification of genetic polymorphisms that influence the efficacy and safety of therapies for breast cancer may allow future treatments to be individualised based not only on tumour characteristics but also on host genetics. Genetic factors that affect the metabolism, efficacy and safety of tamoxifen, one of the most common drugs used for the treatment and prevention of breast cancer, have received particular attention. Cytochrome P450 2D6 (CYP2D6) is crucial in the metabolism of tamoxifen to its active metabolite endoxifen. Women with genetic variants of CYP2D6 or who take drugs that inhibit the enzyme have low endoxifen plasma concentrations and may show reduced benefits to tamoxifen treatment. CYP2D6 polymorphisms and variants in other candidate genes may also influence secondary benefits and side effects of tamoxifen. Here, we summarise data suggesting that CYP2D6 status may be an important predictor of the benefits of tamoxifen to an individual; in addition, we briefly discuss the role of variants in other candidate genes. Whether CYP2D6 status should be determined prior to initiating tamoxifen therapy is currently under debate and may be appropriate only for select women who are candidates for tamoxifen alone but for whom alternative standard options are available.

An assessment of drug-drug interactions: the effect of desvenlafaxine and duloxetine on the pharmacokinetics of the CYP2D6 probe desipramine in healthy subjects

A number of antidepressants inhibit the activity of the cytochrome P450 2D6 enzyme system, which can lead to drug-drug interactions. Based on its metabolic profile, desvenlafaxine, administered as desvenlafaxine succinate, a new serotonin-norepinephrine reuptake inhibitor, is not expected to have an impact on activity of CYP2D6. This single-center, randomized, open-label, four-period, crossover study was undertaken to evaluate the effect of multiple doses of desvenlafaxine (100 mg/day, twice the recommended therapeutic dose for major depressive disorder in the United States) and duloxetine (30 mg b.i.d.) on the pharmacokinetics (PK) of a single dose of desipramine (50 mg). A single dose of desipramine was given first to assess its PK. Desvenlafaxine or duloxetine was then administered, in a crossover design, so that steady-state levels were achieved; a single dose of desipramine was then coadministered. The geometric least-square mean ratios (coadministration versus desipramine alone) for area under the plasma concentration versus time curve (AUC) and peak plasma concentrations (C(max)) of desipramine and 2-hydroxydesipramine were compared using analysis of variance. Relative to desipramine alone, increases in AUC and C(max) of desipramine associated with duloxetine administration (122 and 63%, respectively) were significantly greater than those associated with desvenlafaxine (22 and 19%, respectively; P < 0.001). Duloxetine coadministered with desipramine was also associated with a decrease in 2-hydroxydesipramine C(max) that was significant compared with the small increase seen with desvenlafaxine and desipramine (-24 versus 9%; P < 0.001); the difference between changes in 2-hydroxydesipramine AUC did not reach statistical significance (P = 0.054). Overall, desvenlafaxine had a minimal impact on the PK of desipramine compared with duloxetine, suggesting a lower risk for CYP2D6-mediated drug interactions.