Effects on cerebral blood flow after single doses of the ß2 agonist, clenbuterol, in healthy volunteers and patients with mild cognitive impairment or Parkinson's disease.

AIMS: Cerebral hypometabolism occurs years prior to a diagnosis of neurodegenerative diseases and coincides with reduced cerebral perfusion and declining noradrenergic transmission from the locus coeruleus. In pre-clinical models, ß-adrenoceptor (ß-AR) agonists increase cerebrocortical glucose metabolism, and may have therapeutic potential for neurodegenerative diseases. This study investigated the safety and effects on regional cerebral blood flow (rCBF) of the oral, brain-penetrant ß2-AR agonist, clenbuterol, in healthy volunteers (HV) and patients with mild cognitive impairment (MCI) or Parkinson's disease (PD). METHODS: This study evaluated the safety and effects on cerebral activity of the oral, brain-penetrant, ß2-AR agonist clenbuterol (20-160 µg) in healthy volunteers and patients with MCI or PD. Regional CBF, which is tightly coupled to glucose metabolism, was measured by arterial spin labelling MRI in 32 subjects (25 HV and 8 MCI or PD) across five cohorts. In some cohorts, low doses of nadolol (1-5 mg), a ß-AR antagonist with minimal brain penetration, were administered with clenbuterol to control peripheral ß2-AR responses. RESULTS: Significant, dose-dependent increases in rCBF were seen in multiple brain regions, including hippocampus, amygdala and thalamus, following the administration of clenbuterol to HVs (mean changes from baseline in hippocampal rCBF of -1.7%, 7.3%, 22.9%, 28.4% 3 h after 20, 40, 80 and 160 µg clenbuterol, respectively). In patients with MCI or PD, increases in rCBF following 80 µg clenbuterol were observed both without and with 5 mg nadolol (in hippocampus, 18.6%/13.7% without/with nadolol). Clenbuterol was safe and well-tolerated in all subjects; known side effects of ß2-agonists, including increased heart rate and tremor, were mild in intensity and were blocked by low-dose nadolol. CONCLUSIONS: The effects of clenbuterol on rCBF were evident both in the absence and presence of low-dose nadolol, suggesting central nervous system (CNS) involvement. Concomitant inhibition of the peripheral effects of clenbuterol by nadolol confirms that meaningful ß2-AR antagonism in the periphery was achieved without interrupting the central effects of clenbuterol on rCBF.

A HPLC-MS/MS method for the determination of Nadolol in rat plasma: Development, validation, and application to pharmacokinetic study.

A sensitive validated method has been developed for the quantification of Nadolol in rat plasma by high performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) using deuterated Nadolol (Nadolol D9) as internal standard (IS). The liquid-liquid extraction method using ethyl acetate was employed for the sample pretreatment. The separation was achieved on the Agilent Zorbax XDB C18 column (150 mm × 4.6 mm ID., 3.5 µm). The column temperature was controlled at 30°C. The components were eluted by using mobile phase A (10 mM ammonium formate) and mobile phase B (acetonitrile) in the ratio of 20:80 v/v with a flow rate of 0.5 mL/min. And 15 µL aliquot was injected in an isocratic elution mode with a total run time of 2.5 min. The multiple reactions monitoring transitions, m/z 310.20/254.10 for Nadolol and IS 319.20/255.00 were selected to achieve high selective analysis. The method exhibited great selectivity and linearity over the concentration range of 6 to 3000 ng/mL. The lower limit of quantification was found to be 6 ng/mL. The developed method proved acceptable results on selectivity, sensitivity, precision, accuracy, and stability studies as per Food and Drug Administration guidelines. This HPLC-MS/MS assay was successfully applied to get the pharmacokinetics parameters in rat plasma.

Current management of inherited arrhythmia syndromes associated with the cardiac ryanodine receptor.

PURPOSE OF REVIEW: Gain-of-function variants in the gene encoding the cardiac ryanodine receptor ( RYR2 ) are associated with catecholaminergic polymorphic ventricular tachycardia (CPVT). The exercise stress test (EST) has long been fundamental in diagnosis and management, but recent work has further explored its role. A new entity termed calcium release deficiency syndrome (CRDS) has been associated with loss-of-function RYR2 variants and a different arrhythmic phenotype. RECENT FINDINGS: Standard EST is not perfectly reproducible with regards to provocation of arrhythmia in CPVT. A newly described burst EST protocol may be more sensitive in this regard. Nadolol is the most effective beta blocker in CPVT, though arrhythmic events remain frequent and dual therapy with flecainide and/or left cardiac sympathetic denervation may add protection. A recent report renews debate regarding the use of implantable defibrillator therapy in CPVT. CRDS is characterized by later age of presentation, normal/near normal EST, and ventricular arrhythmia induced by a novel ventricular stimulation protocol. SUMMARY: Burst EST may aid in the diagnosis and management of CPVT. Nadolol is the preferred beta blocker in CPVT, and consideration should be given to early dual therapy. CRDS should be suspected in patients with arrhythmic events, rare RYR2 variants, and a phenotype inconsistent with CPVT.

Clinical pharmacokinetics of nadolol: A systematic review.

WHAT IS KNOWN AND OBJECTIVE: Nadolol is a non-selective beta-adrenergic antagonist that is used for the treatment of hypertension and angina. The primary route for its administration is oral. It is given once daily as it has a longer half-life (t½). The purpose of conducting this systematic review is to provide a comprehensive view of all the available pharmacokinetic (PK) data on nadolol in humans. This review aimed to systematically collate and analyze publish data on the clinical PK of nadolol in humans and this can be beneficial for the clinicians in dosage adjustments. METHODS: Two electronic databases PubMed and Google Scholar were used for conducting a systematic literature search. All the relevant articles containing PK data of nadolol in humans were retrieved. A total of 1275 articles were searched from both databases and after applying eligibility criteria finally, 22 articles were included for conducting the systematic review. RESULTS AND DISCUSSION: The area under the plasma concentration curve (AUC) and maximum plasma concentration (Cmax ) of nadolol increased in a dose-dependent manner. The t½ of nadolol was increased to double (18.2-68.6 h) in the patients with chronic kidney disease while the serum t½ became shorter (3.2-4.3 h) when administered to the children. The bioavailability of nadolol was greatly reduced by the coadministration of green tea. Nadolol can be effectively removed by hemodialysis. It undergoes enterohepatic circulation thus activated charcoal decreased its bioavailability. WHAT IS NEW AND CONCLUSION: Since, there is no previous report of a systematic review on the PK of nadolol, the current review encompasses all the relevant published articles on nadolol in humans. The analysis and understanding of PK parameters (AUC, Cmax , and t½) of nadolol may be helpful in the development and evaluation of PK models.

Hair analysis for beta-blockers and calcium-channel blockers by using liquid chromatography-tandem mass spectrometry as a tool for monitoring adherence to antihypertensive therapy.

Adherence to therapy is the key to a successful therapeutic intervention, especially in cardiovascular diseases in which a lack of adherence may have serious consequences in terms morbidity and/or mortality. In this context, hair analysis can be an excellent tool to monitor adherence to therapy. Indeed, drugs present in blood are incorporated into the hair matrix, where drugs and metabolites can stay unaltered for a long time protected from metabolism and degradation. In the present study, a simple, specific, and sensitive ultra-high performance liquid-chromatography-tandem mass spectrometry (UHPLC-MS/MS) method set up to determine in human hair seven beta-blockers (viz., metoprolol, sotalol, labetalol, atenolol, nebivolol, bisoprolol, and nadolol) and two calcium-channel blockers (lercanidipine and amlodipine), which are widely prescribed to treat medium-to-severe hypertensive conditions. The optimized method was successfully validated in terms of accuracy, repeatability, reproducibility, matrix effect and extraction recovery. Moreover, the applicability of the method was evaluated by analyzing 34 real samples of hair obtained from patients under long-term therapy with calcium channel blockers and beta-blockers.

Contemporary maternal and fetal outcomes in the treatment of LQTS during pregnancy: Is nadolol bad for the fetus?

BACKGROUND: ß-Blocker therapy, specifically nadolol, is the recommended treatment for long QT syndrome (LQTS). Previous studies assessing maternal and fetal outcomes were published before the nadolol era. OBJECTIVE: The purpose of this study was to examine contemporary maternal and fetal outcomes in the treatment of LQTS during pregnancy. METHODS: We queried the Inherited Arrhythmia Database at Cleveland Clinic and identified all pregnant patients with LQTS from January 2001 through January 2020. Collected data included use and timing of ß-blockers, maternal arrhythmic events, fetal growth restriction, neonatal hypoglycemia, and bradycardia. RESULTS: Among 68 live-birth pregnancies in 31 women with LQTS (mean age 29 ± 5.9 years; mean corrected QT interval 468 ± 39 ms), there were 5 arrhythmic events in 4 mothers. All arrhythmic events occurred in the postpartum period, and there were no arrhythmic events in patients taking ß-blockers. In patients diagnosed with LQTS and treated with ß-blockers (n = 27 [41%]), nadolol was the most commonly prescribed agent throughout pregnancy and the postpartum period (n = 16 [60%]). The rate of intrauterine growth restriction was not significantly different in fetuses exposed to ß-blockers vs unexposed (P = .08). In the postnatal period, hypoglycemia was not seen and 1 patient in the exposure group had bradycardia. CONCLUSION: Arrhythmic events were only seen in the postpartum period in those not treated with ß-blockers. Events occurred as late as 9 months postpartum. ß-Blocker therapy, specifically nadolol, was not associated with a higher incidence of intrauterine growth restriction. Moreover, neonatal bradycardia was rare and hypoglycemia was not observed.

Outcomes of Patients With Catecholaminergic Polymorphic Ventricular Tachycardia Treated With ß-Blockers.

Importance: Patients with catecholaminergic polymorphic ventricular tachycardia (CPVT) may experience life-threatening arrhythmic events (LTAEs) despite ß-blocker treatment. Further complicating management, the role of implantable cardioverter defibrillator (ICD) in CPVT is debated. Objective: To investigate the long-term outcomes of patients with RYR2 CPVT treated with ß-blockers only and the cost to benefit ratio of ICD. Design, Settings, and Participants: This prospective cohort study conducted from January 1988 to October 2020 with a mean (SD) follow-up of 9.4 (7.5) years included patients who were referred to the Molecular Cardiology Clinics of ICS Maugeri Hospital, Pavia, Italy. Participants included consecutive patients with CPVT who were carriers of a pathogenic or likely pathogenic RYR2 variant with long-term clinical follow-up. Exposures: Treatment with selective and nonselective ß-blocker only and ICD implant when indicated. Main Outcome and Measures: The main outcome was the occurrence of the first LTAE while taking a ß-blocker. LTAE was defined as a composite of 3 hard end points: sudden cardiac death, aborted cardiac arrest, and hemodynamically nontolerated ventricular tachycardia. Results: The cohort included 216 patients with RYR2 CPVT (121 of 216 female [55%], median [IQR] age 14, [9-30] years). During a mean (SD) follow-up of 9.4 (7.5) years taking ß-blockers only, 28 of 216 patients (13%) experienced an LTAE (annual rate, 1.9%; 95% CI, 1.3-2.7). In multivariable analysis, experiencing either an LTAE (hazard ratio [HR], 3.3; 95% CI, 1.2-8.9; P = .02) or syncope before diagnosis (HR, 4.5; 95% CI, 1.8-11.1; P = .001) and carrying a C-terminal domain variant (HR, 18.1; 95% CI, 4.1-80.8; P < .001) were associated with an increased LTAE risk during ß-blocker therapy only. The risk of LTAE among those taking selective ß-blockers vs nadolol was increased 6-fold (HR, 5.8; 95% CI, 2.1-16.3; P = .001). Conversely, no significant difference was present between propranolol and nadolol (HR, 1.8; 95% CI, 0.4-7.3; P = .44). An ICD was implanted in 79 of 216 patients (37%) who were followed up for a mean (SD) of 8.6 (6.3) years. At the occurrence of LTAE, ICD carriers were more likely to survive (18 of 18 [100%]) than non-ICD carriers (6 of 10 [60%]; P = .01). Conclusions and Relevance: In this cohort study, selective ß-blockers were associated with a higher risk of LTAE as compared with nadolol. Independently from treatment, LTAE and syncope before diagnosis and C-terminal domain variants identified patients at higher risk of ß-blocker failure, and the ICD was associated with reduced mortality in high-risk patients with CPVT.

Noninferiority and Safety of Nadolol vs Propranolol in Infants With Infantile Hemangioma: A Randomized Clinical Trial.

Importance: Propranolol for infantile hemangiomas (IH) has been shown to be effective and relatively safe. However, other less lipophilic ß-blockers, such as nadolol, may be preferable in individuals who experience propranolol unresponsiveness or adverse events. Objective: To document the noninferiority and safety of oral nadolol compared with oral propranolol in infants with IH. Design, Setting, and Participants: This double-blind noninferiority prospective study with a noninferiority margin of 10% compared propranolol with nadolol in infants aged 1 to 6 months with problematic IH. The study was conducted in 2 academic pediatric dermatology centers in Canada between 2016 and 2020. Infants aged 1 to 6 months with a hemangioma greater than 1.5 cm on the face or 3 cm or greater on another body part causing or with potential to cause functional impairment or cosmetic disfigurement. Interventions: Oral propranolol and nadolol in escalating doses up to 2 mg/kg/d. Main Outcomes and Measure: Between-group differences comparing changes in the bulk (size and extent) and color of the IH at week 24 with baseline using a 100-mm visual analog scale. Results: The study included 71 patients. Of these, 36 were treated with propranolol. The mean (SD) age in this group was 3.1 (1.4) months, and 31 individuals (86%) were female. Thirty-five infants were treated with nadolol. The mean (SD) age in this group was 3.2 (1.6) months, and 26 individuals (74%) were female. The difference in IH between groups by t test was 8.8 (95% CI, 2.7-14.9) for size and 17.1 (95% CI, 7.2-30.0) for color in favor of the nadolol group, demonstrating that nadolol was noninferior to propranolol. Similar differences were noted at 52 weeks: 6.0 (95% CI, 1.9-10.1) and 10.1 (95% CI, 2.9-17.4) for size and color improvement, respectively. For each doubling of time unit (week), the coefficient of involution was 2.4 (95% CI, 0.5-4.4) higher with nadolol compared with propranolol. Safety data were similar between the 2 interventions. Conclusions and Relevance: Oral nadolol was noninferior to oral propranolol, indicating it may be an efficacious and safe alternative in cases of propranolol unresponsiveness or adverse events, or when faster involution is required. Trial Registration: ClinicalTrials.gov Identifier: NCT02505971.

Oral epigallocatechin gallate reduces intestinal nadolol absorption via modulation of Oatp1a5 and Oct1 transcriptional levels in spontaneously hypertensive rats.

BACKGROUND: Concurrent use of epigallocatechin-3-gallate (EGCG) and medication may lead to botanical-drug interactions, subsequently therapeutic failure or drug toxicity. It has been reported that EGCG reduces plasma nadolol bioavailability in normotensive models. Nevertheless, evidence on the effects of EGCG on hypertensive model, and the possible underlying mechanism have not been elucidated. OBJECTIVES: This study aims (i) to investigate the effects of EGCG on nadolol pharmacokinetics (maximum plasma concentration, time to achieve maximum concentration, area under the time-plasma concentration curve, plasma half-life and total clearance) and subsequently its impact on blood pressure control; and (ii) to identify transcriptional regulatory roles of EGCG on the nadolol intestinal and hepatic drug-transporters in SHR. METHODS: Male SHR were pre-treated with a daily dose of EGCG (10 mg/kg body weight, i.g.) for 13 days. On day-14, a single dose of nadolol (10 mg/kg body weight) was given to the rats 30 min after the last dose of EGCG administration. Systolic blood pressure (SBP) was measured at 6-h and 22-h post-nadolol administration. Plasma and urinary nadolol concentrations were quantified using high-performance liquid chromatography, and pharmacokinetic parameters were analyzed by using non-compartmental analysis. Hepatic and ileal Oatp1a5, P-gp, and Oct1 mRNA expressions were determined by real-time PCR. RESULTS: SBP of SHR pre-treated with EGCG and received nadolol was significantly higher than those which were not pre-treated with EGCG but received nadolol. Pre-treatment of EGCG resulted in a marked reduction of plasma nadolol maximum concentration (Cmax) and area under the time-plasma concentration curve (AUC) by 53% and 51% compared to its control. The 14-day treatment with oral EGCG led to a significant downregulation of mRNA levels of ileal Oatp1a5, P-gp, and Oct1 genes by 4.03-, 8.01- and 4.03-fold; and hepatic P-gp, and Oct1 genes by 2.61- and 2.66-fold. CONCLUSION: These data concluded that exposure to EGCG could lead to reduced nadolol bioavailability and therefore, uncontrolled raised blood pressure and higher risks of cardiovascular events. Our data suggest that the reduced nadolol bioavailability is associated with the downregulation of ileal Oatp1a5 and Oct1 mRNA levels that subsequently lead to poor absorption of nadolol to the systemic circulation.

Stability of Extemporaneously Compounded Nadolol 10-mg/mL Suspension in Oral Mix in Glass and Plastic Bottles and Plastic Syringes.

An oral liquid formulation of nadolol, which is required for administration to patients who cannot swallow intact tablets, is not commercially available. The objective of this study was to evaluate the stability of nadolol 10 mg/mL prepared in Oral Mix vehicle and stored in amber glass, amber polyethylene terephthalate, or amber polyvinyl chloride for 91 days at 4ÆC and 25ÆC; and polypropylene oral plastic syringes at 25ÆC only. Three separate batches of nadolol suspension 10 mg/mL were prepared with Oral Mix. Of the suspension, 50-mL aliquots were stored in 100-mL bottles (amber glass, amber polyethylene terephthalate, or amber polyvinyl chloride). Half of the bottles from each container type were stored at 25ÆC and the other half at 4ÆC. On study days 0, 2, 7, 14, 21, 28, 42, 56, 72, and 91, nadolol concentration was determined using a reverse-phase, stability-indicating liquid chromatographic method from samples drawn from each type of container at each temperature. Oral syringes (3 mL), filled with 2 mL of suspension, were stored at 25ÆC and tested on days 0, 2, 7, 21, 42, and 91. The concentration of nadolol 10 mg/mL in Oral Mix in all study samples from bottles and oral syringes remained within 3.5% of the initial concentration. Based on the fastest degradation rate with 95% confidence, on day 91, between 99% to 100% and 98% to 100% remained in suspensions stored in bottles at 25ÆC and 4ÆC, respectively. Oral syringes at 25ÆC had 94% remaining on day 91. Multiple linear regression analysis demonstrated that the percent remaining was related to study day and container, but not temperature. On day 91, nadolol 10 mg/mL oral suspensions prepared with Oral Mix and stored in all bottle types at 4ÆC will retain more than 98% of the initial concentration compared to 99% at 25ÆC and only 94% when stored in oral syringes.

Dose response to nadolol in congenital long QT syndrome.

BACKGROUND: Beta-blocker therapy is the cornerstone of treatment for patients with long QT syndrome (LQTS). Few details on the dose to be used are available. As the response is variable between patients, we systematically evaluated the effect of treatment by performing an exercise test. OBJECTIVE: The purpose of this study was to explore dose response to nadolol on exercise test in LQTS patients in order to propose a more personalized therapeutic approach. METHODS: LQTS patients followed at the Reference Centre for Hereditary Arrhythmic Diseases of Nantes with at least 1 exercise test under nadolol were included retrospectively between 1993 and 2017. All patients underwent gradual cycle exercise tests. Doses adjusted to weight and response to treatment were recorded and evaluated by the percentage of age-predicted maximum heart rate reached on exercise test. RESULTS: Ninety-five patients were included in the study, and 337 stress tests under nadolol were analyzed. No correlation existed between dose and percentage of age-predicted maximum heart rate on exercise tests. Twenty-one patients were overresponders, mostly LQTS1, and 20 were underresponders, mainly LQTS2 (P = .0229). Forty-two patients had at least 3 stress tests under nadolol. We found a negative correlation between dose change and percentage of age-predicted maximum heart rate change (P <.0001). We then proposed a table to adapt dose according to exercise test response. CONCLUSION: Our study demonstrated a major variability of dose response to nadolol in patients with LQTS, thus underlining the need for a tailored dosage for each patient. Intraindividual analysis showed a relatively constant dose-response relationship, allowing guided dose adaptation after the first exercise test.

Propranolol versus nadolol for treatment of pediatric subglottic hemangioma.

PURPOSE: The beta-blocker propranolol is the standard medical therapy for subglottic hemangioma (SGH), but side effects and incomplete response rates require close monitoring. Nadolol has been identified as a potential alternative but its use has not been examined for SGH. METHODS: Single institution retrospective cohort study of pediatric SGH treated with propranolol or nadolol. RESULTS: Thirteen children (1 male, 12 female) with SGH were included: 6 were treated with propranolol (2.0-3.5 mg/kg/d) and 7 with nadolol (2.0-4.0 mg/kg/d). The most common presenting symptom was stridor (85%) and mean (SD) symptom duration prior to diagnosis was 4.6 (3.8) weeks. Cutaneous vascular lesions were present in 54%. There were 7 right-sided, 5 left-sided and 1 bilateral SGH. The mean (SD) percentage of airway obstruction was 60.6% (27.4). The response rate was 100% (6/6) for propranolol and 85.7% (6/7) for nadolol (p = 0.36). Mean (SD) time to symptomatic improvement was 2.6 (2.2) days with no difference across groups (p = 0.71). There was no hypotension, hypoglycemia, weight loss, or sleep disturbances in either group. One patient in the propranolol group experienced vomiting. Two patients in the nadolol group required dosage reduction due to asymptomatic bradycardia. The mean (SD) duration of admission was 14.4 (12.6) days and duration of treatment was 13.8 (11.2) days with no difference across groups (p = 0.23; p = 0.31, respectively). All patients had treatment initiated as inpatients and completed as outpatients. CONCLUSION: Children with SGH treated with propranolol or nadolol had similar response rates and side effect profiles.

Supraventricular tachycardias in the first year of life: what is the best pharmacological treatment? 24 years of experience in a single centre.

BACKGROUND: Supraventricular tachycardias (SVTs) are common in the first year of life and may be life-threatening. Acute cardioversion is usually effective, with both pharmacological and non-pharmacological procedures. However, as yet no international consensus exists concerning the best drug required for a stable conversion to sinus rhythm (maintenance treatment). Our study intends to describe the experience of a single centre with maintenance drug treatment of both re-entry and automatic SVTs in the first year of life. METHODS: From March 1995 to April 2019, 55 patients under one year of age with SVT were observed in our Centre. The SVTs were divided into two groups: 45 re-entry and 10 automatic tachycardias. As regards maintenance therapy, in re-entry tachycardias, we chose to start with oral flecainide and in case of relapses switched to combined treatment with beta-blockers or digoxin. In automatic tachycardias we first administered a beta-blocker, later combined with flecainide or amiodarone when ineffective. RESULTS: The patients' median follow-up time was 35 months. In re-entry tachycardias, flecainide was effective as monotherapy in 23/45 patients (51.1%) and in 20/45 patients (44.4%) in combination with nadolol, sotalol or digoxin (overall 95.5%). In automatic tachycardias, a beta-blocker alone was effective in 3/10 patients (30.0%), however, the best results were obtained when combined with flecainide: overall 9/10 (90%). CONCLUSIONS: In this retrospective study on pharmacological treatment of SVTs under 1 year of age the combination of flecainide and beta-blockers was highly effective in long-term maintenance of sinus rhythm in both re-entry and automatic tachycardias.

The effects of normoxic endurance exercise on erythropoietin (EPO) production and the impact of selective ß1 and non-selective ß1 + ß2 adrenergic receptor blockade.

PURPOSE: Habitual endurance exercise results in increased erythropoiesis, which is primarily controlled by erythropoietin (EPO), yet studies demonstrating upregulation of EPO via a single bout of endurance exercise have been equivocal. This study compares the acute EPO response to 30 min of high versus 90 min of moderate-intensity endurance exercise and whether that response can be upregulated via selective adrenergic receptor blockade. METHODS: Using a counterbalanced, cross-over design, fifteen participants (age 28 ± 8) completed two bouts of running (30-min, high intensity vs 90-min, moderate intensity) matched for overall training stress. A separate cohort of fourteen participants (age 31 ± 6) completed three bouts of 30-min high-intensity cycling after ingesting the preferential ß1-adrenergic receptor (AR) antagonist bisoprolol, the non-preferential ß1 + ß2 antagonist nadolol or placebo. Venous blood was collected before, during, and after exercise, and serum EPO levels were determined by ELISA. RESULTS: No detectable EPO response was observed during or after high intensity running, however, in the moderate-intensity trial EPO was significantly elevated at both during-exercise timepoints (+ 6.8% ± 2.3% at 15 min and + 8.7% ± 2.2% at 60 min). No significant change in EPO was observed post-cycling or between the trials involving ßAR blockade. CONCLUSION: Neither training mode (running or cycling), nor beta-blockade significantly influenced the EPO response to 30 min of high-intensity exercise, however, 90 min of moderate-intensity running elevated EPO during exercise, returning to baseline immediately post-exercise. Identifying the optimal mode, duration and intensity required to evoke an EPO response to exercise may help tailor exercise prescriptions designed to maximize EPO response for both performance and clinical applications.

Urinary Excretion of Nadolol as a Possible In Vivo Probe for Drug Interactions Involving P-Glycoprotein.

Nadolol is a hydrophilic and nonselective ß-adrenoceptor blocker with a bioavailability of 30%, relatively longer half-life, negligible metabolism, and predominant renal excretion. Previous studies have reported that nadolol is a substrate of P-glycoprotein, and the coadministration with itraconazole, a typical P-glycoprotein inhibitor, results in elevated plasma concentrations and cumulative urinary excretion of nadolol. In this study, we assessed whether measurements of urinary-excreted nadolol can be an alternative method of plasma pharmacokinetics for P-glycoprotein-mediated drug interactions in humans. We reanalyzed the pooled data set of plasma concentration and urinary excretion of nadolol from our previous clinical studies in a total of 32 healthy Japanese adults. The area under the plasma concentration-time curve from 0 to infinity (AUC0-∞ ) of nadolol in individual subjects was significantly correlated with the maximum plasma concentration (r = 0.80, P < .01) and the cumulative amount excreted into urine (Ae ) at 4 (r = 0.51, P = .01), 8 (r = 0.63, P < .01), 24 (r = 0.75, P < .01), and 48 (r = 0.77, P < .01) hours. Significant correlations were also observed between the AUC and Ae during the same respective periods. In the drug interactions of nadolol with itraconazole, rifampicin, a well-known P-glycoprotein inducer, or grapefruit juice, there were significant correlations between the differences in AUC0-48 and those in Ae, 0-48 from the controls in individual subjects. These results suggest that the measurements of urinary excretion of nadolol can be employed as a sensitive and reliable alternative to plasma pharmacokinetics for the evaluation of P-glycoprotein-mediated drug interactions.

ß-Blocker Use and Risk of Mortality in Heart Failure Patients Initiating Maintenance Dialysis.

RATIONAL & OBJECTIVE: Beta-blockers are recommended for patients with heart failure (HF) but their benefit in the dialysis population is uncertain. Beta-blockers are heterogeneous, including with respect to their removal by hemodialysis. We sought to evaluate whether ß-blocker use and their dialyzability characteristics were associated with early mortality among patients with chronic kidney disease with HF who transitioned to dialysis. STUDY DESIGN: Retrospective cohort study. SETTING & PARTICIPANTS: Adults patients with chronic kidney disease (aged≥18 years) and HF who initiated either hemodialysis or peritoneal dialysis during January 1, 2007, to June 30, 2016, within an integrated health system were included. EXPOSURES: Patients were considered treated with ß-blockers if they had a quantity of drug dispensed covering the dialysis transition date. OUTCOMES: All-cause mortality within 6 months and 1 year or hospitalization within 6 months after transition to maintenance dialysis. ANALYTICAL APPROACH: Inverse probability of treatment weights using propensity scores was used to balance covariates between treatment groups. Cox proportional hazard analysis and logistic regression were used to investigate the association between ß-blocker use and study outcomes. RESULTS: 3,503 patients were included in the study. There were 2,115 (60.4%) patients using ß-blockers at transition. Compared with nonusers, the HR for all-cause mortality within 6 months was 0.79 (95% CI, 0.65-0.94) among users of any ß-blocker and 0.68 (95% CI, 0.53-0.88) among users of metoprolol at transition. There were no observed differences in all-cause or cardiovascular-related hospitalization. LIMITATIONS: The observational nature of our study could not fully account for residual confounding. CONCLUSIONS: Beta-blockers were associated with a lower rate of mortality among incident hemodialysis patients with HF. Similar associations were not observed for hospitalizations within the first 6 months following transition to dialysis.