Anti-arrhythmic action of nadolol, a beta-adrenergic receptor blocking agent

A Comprehensive Physiologically Based Pharmacokinetic Model of Nadolol in Adults with Renal Disease and Pediatrics with Supraventricular Tachycardia

Nadolol is a long-acting non-selective β-adrenergic antagonist that helps treat angina and hypertension. The current study aimed to develop and validate the physiologically based pharmacokinetic model (PBPK) of nadolol in healthy adults, renal-compromised, and pediatric populations. A comprehensive PBPK model was established by utilizing a PK-Sim simulator. After establishing and validating the model in healthy adults, pathophysiological changes i.e., blood flow, hematocrit, and GFR that occur in renal failure were incorporated in the developed model, and the drug exposure was assessed through Box plots. The pediatric model was also developed and evaluated by considering the renal maturation process. The validation of the models was carried out by visual predictive checks, calculating predicted to observed (Rpre/obs) and the average fold error (AFE) of PK parameters i.e., the area under the concentration-time curve (AUC0-t), the maximum concentration in plasma (Cmax), and CL (clearance). The presented PBPK model successfully simulates the nadolol PK in healthy adults, renal-impaired, and pediatric populations, as the Rpre/obs values of all PK parameters fall within the acceptable range. The established PBPK model can be useful in nadolol dose optimization in patients with renal failure and children with supraventricular tachycardia.

Survey of Pharmacological Activity and Pharmacokinetics of Selected β-Adrenergic Blockers in Regard to Their Stereochemistry

The present survey concentrates on pharmacodynamics and pharmacokinetics of selected β-adrenergic blockers from the point of view of their stereochemistry. It could be shown that the activity in the arylaminoethanol and aryloxyaminopropanol group of β-blockers is higher in their (–)-enantiomers as compared with the (+)-enantiomers. The stereoisomers differ also in other types of bioactivity as well as in toxicity. The particular pharmacokinetic stages such as resorption, distribution, and metabolism are discussed in regard to their stereochemistry.

Holter-guided identification of premature ventricular contractions susceptible to suppression by beta-blockers

To evaluate whether the identification of the different types of relations between premature ventricular contractions (PVCs) and the preceding sinus cycle length is capable of predicting the effect of beta-blockers on the PVCs themselves, 55 patients (43 men, 12 women, mean age 52.6 +/- 15.6 years) with different cardiac diseases, and >30 PVCs/hr characterized by stability and the same relation at two Holter monitoring periods were studied. The relation was tachycardia enhanced (the shorter the preceding cycle length, the higher the incidence of PVCs) in 23 patients (group 1); indifferent (no correlation between the preceding cycle length and PVC incidence) in 21 (group 2); and bradycardia enhanced (the longer the preceding cycle length, the higher the incidence of PVCs) in 11 (group 3). A third Holter monitoring was performed 6 days after nadolol administration (80 mg/day) to evaluate its effect on the three types of PVCs. Incidence in all patients (-88;p<0.001). In group 2, it caused a reduction in the majority of patients (-60%;p<0.05) but an increase in five. In group 3, it caused a reduction in only half of the patients (-45%) and a 91% increase in the remainder. The difference in the effect of nadolol in the three groups was highly significant (X2=27.5;p<0.0001). The relation between the incidence of PVCs and the preceding cycle length is a useful means of identifying subsets of patients with PVCs who will benefit from beta-blockers.

Digitalis glycosides: a discussion of the similarities and differences in actions and existing controversies

The writing of this review was initiated to answer the question of whether differences in the actions of the various digitalis glycosides exist and to discuss current controversies in the research area of the digitalis glycosides. Data obtained in our laboratory indicated that the effect of digoxin on postganglionic cardiac sympathetic neural discharge in the minute prior to the occurrence of arrhythmia differed from that of ouabain. This raised the question of whether data published in other laboratories would support the contention that differences in glycosides do exist. To answer this question, a review of the literature was begun. Our survey of these studies are cited in the tables of this review. These tables summarize the actions of glycosides in vivo and in vitro in different animal models. The reader should bear in mind that the data included within the tables do not represent an inclusive summary of all studies in the literature. For detailed review articles, the reader is referred to the following references: Gillis et al; Gillis and Quest; Roberts et al; Lathers and Roberts; Farah and Alousi; Benthe; Levitt et al; Smith and Haber; Somberg; Lee and Klaus; Mason; Schwartz. Furthermore the summary of the results for each particular study cited in the table may not, in all cases, include each finding of the published data. Nevertheless, the tables do provide a summary of data obtained in various species with different glycosides in several different areas of research, and as such, represent an abridged compendium for the research working in the field of digitalis glycosides. This review has been organized firstly to consider glycoside-induced alterations in the autonomic nervous system and, secondly, to examine their direct actions on the heart.

Reduction in digitalis-associated postinfarction mortality with nadolol in conscious dogs

Previously, we have demonstrated an increased incidence of lethal ischemic arrhythmias in postinfarction dogs with clinically observable serum digoxin concentrations, and a significant reduction in digitalis-related lethal ischemic arrhythmias after subacute left stellectomy. In the present study, the protective actions of acute beta-adrenoceptor blockade with nadolol, 1.0 mg/kg administered intravenously immediately preceding the induction of posterolateral myocardial ischemia, were assessed in conscious dogs with recent, small anterior myocardial infarctions pretreated with digoxin, 0.0125 mg/kg/day intravenously, for 5 to 7 consecutive days (total n = 11). A cohort of postinfarction dogs pretreated with digoxin alone served as a control group (total n = 26). Pre vs postdigoxin electrophysiologic testing indicated reductions in myocardial refractoriness in ventricular noninfarct and infarct zones in both treatment groups, whereas the administration of nadolol tended to reverse the reductions in ventricular refractoriness. Arrhythmia-related deaths in response to posterolateral myocardial ischemia were reduced from 12 of 20 (60%) in the digoxin control group to 2 of 10 (20%) in the digoxin + nadolol group (p = 0.039). Serum digoxin concentrations (1.29 +/- 0.14 ng/ml vs 1.39 +/- 0.24 ng/ml), underlying anterior myocardial infarct size (6.9 +/- 1.5% vs 4.6 +/- 0.9% of left ventricle), and developing posterolateral myocardial infarct size (22.8 +/- 2.5% vs 17.5 +/- 3.6% of left ventricle) did not differ significantly between the digoxin and digoxin + nadolol groups. Acute beta-adrenoceptor blockade with nadolol appears to reduce digitalis-mediated ischemic postinfarction mortality, possibly because of a salutary increase in ventricular refractoriness.

Electrophysiologic effects, clinical efficacy and safety of intravenous and oral nadolol in refractory supraventricular tachyarrhythmias

The electrocardiographic and electrophysiologic effects, clinical efficacy and safety of intravenous and oral nadolol therapy were examined in 34 patients with recurrent supraventricular tachyarrhythmias (SVT) undergoing electrophysiologic evaluation. Programmed electrical stimulation was performed in the control (drug-free) state, after infusion of intravenous nadolol (mean dose 0.09 +/- 0.03 mg/kg) and after chronic oral nadolol therapy in patients who responded to intravenous nadolol (mean dose 83 +/- 12 mg for 5 days). Intravenous nadolol administration prolonged mean sinus cycle length (p = 0.009), mean PR interval (p = 0.001) and mean AH interval (p = 0.001), with no significant electrophysiologic effects in the atrium, ventricle or accessory bypass tracts. Oral nadolol had similar electrocardiographic and electrophysiologic effects, but of lesser magnitude. Intravenous nadolol resulted in complete suppression of induced SVT in 78% of patients with sinus and atrioventricular nodal reentrant tachycardia and 11% of patients with atrioventricular (AV) reentrant tachycardia (p less than 0.001). Partial responses were frequent in intraatrial or AV reentrant tachycardia (37%). Oral nadolol suppressed induction of SVT in patients who responded to intravenous nadolol. Adverse reactions to intravenous and oral nadolol were infrequent--6% and 8%, respectively--and usually did not require drug withdrawal. Intravenous nadolol is highly effective in sinus and AV nodal reentrant tachycardia, and a successful electrophysiologic response to it predicts efficacy of long-term oral nadolol therapy. It has limited efficacy alone in AV reentrant tachycardia and should be considered in combination with other antiarrhythmic therapy in this type of SVT.

Antiarrhythmic activity of flestolol, a novel ultra-short-acting beta-adrenoceptor antagonist, in the dog

The antiarrhythmic activity of flestolol, an ultra-short acting beta-adrenergic blocker lacking appreciable local anesthetic activity, was examined in several different canine ventricular arrhythmia models. Flestolol, at steady state infusions of 1-1,000 micrograms/kg per min, was generally ineffective in reversing either ouabain-induced or delayed ischemia-induced (24 h Harris dog) ventricular tachycardia. However, flestolol (1, 10 and 100 micrograms/kg per min) produced a dose-dependent decrease in l-norepinephrine (5 micrograms/kg i.v.)-induced ventricular tachycardia in the 5-6 day old Harris dog; the effect of 100 micrograms/kg per min flestolol, 94% suppression of norepinephrine-induced ventricular tachycardia, was completely reversed 60 min after termination of flestolol infusion. In pentobarbital-anesthetized open-chest dogs with pretreatment heart rates greater than or equal to 145 beats/min, flestolol (10 micrograms/kg per min) reduced the incidence of ventricular fibrillation resulting from abrupt coronary artery occlusion compared to placebo-treated controls (15% or 2/13 vs. 70% or 7/10, respectively). These results demonstrate that flestolol has an antiarrhythmic profile consistent with its lack of local anesthetic activity and its ultra-short duration of beta-blockade.

Nadolol and supraventricular tachycardia: an electrophysiologic study

To assess antiarrhythmic efficacy of oral nadolol, 15 patients with recurrent supraventricular tachycardia were studied. Eight patients had atrioventricular (AV) nodal reentrant tachycardia and seven had AV reciprocating tachycardia involving an accessory AV pathway. Electrophysiologic studies were performed before and after intravenous infusion of propranolol (0.20 mg/kg), and were repeated 5 to 8 days after oral nadolol therapy at a daily dose of 80 to 160 mg. Both intravenous propranolol and oral nadolol induced significant prolongation of the sinus cycle length from 741 +/- 73 ms to 834 +/- 97 and 1,029 +/- 95 ms, respectively (p less than 0.001 and p less than 0.0001, respectively). Both intravenous propranolol and oral nadolol depressed AV nodal but not accessory AV pathway conduction, and shifted the dual AV nodal pathway conduction curves (A1A2, A2H2; A1A2, H1H2) upward and to the right by prolonging the conduction time and increasing the refractory period. Ten patients (seven with AV nodal reentry and three with AV reciprocation) who responded to intravenous propranolol also responded to oral nadolol with loss of the inducibility of sustained tachycardia; the remaining five patients (one with AV nodal reentry and four with AV reciprocation) who did not respond to intravenous propranolol also failed to respond to oral nadolol with persistence of the inducibility of sustained tachycardia. Thus, in conclusion, intravenous propranolol testing predicts the therapeutic efficacy of oral nadolol therapy and oral nadolol in once-daily doses may be used for long-term prophylaxis of recurrent supraventricular tachycardia.

Acute electrophysiologic effects of nadolol

The acute effects of intravenous nadolol (0.01 and 0.02 mg/kg) on cardiac electrophysiologic parameters were assessed with His bundle recording and programmed atrial stimulation. The higher dose of nadolol reduced resting heart rate (71 vs. 65 beats/min, P less than 0.02), and the degree of slowing was related to the initial heart rate (r = -0.68, P less than 0.05). Atrioventricular conduction time as defined by the paced A-H interval, rose by 12 msec (P less than 0.001) after nadolol (0.02 mg/kg) administration. Atrial refractoriness increased (by 10 msec, P less than 0.02) only at the higher dose level with nadolol. At both dose levels, atrioventricular nodal effective and functional refractory periods were increased (P less than 0.02) by a mean of 45 and 21 msec, respectively, suggesting greater sensitivity of atrioventricular nodal refractoriness to beta-adrenergic blockade. Nadolol's effects were generally similar to those of previously reported studies with other beta-adrenergic blockers. These data suggest that nadolol slows conduction through the atrioventricular node and increases atrial and atrioventricular nodal refractoriness.

Comparison between atenolol and nadolol in essential hypertension at rest and on exercise

1 The effects of 4 week treatment periods of once-daily atenolol 100 mg, nadolol 80 mg, nadolol 160 mg and placebo on resting and exercise heart rate and blood pressure were compared in a single-blind crossover trial in fifteen patients with essential hypertension. 2 Both atenolol and nadolol, irrespective of dose, reduced resting and exercise blood pressures to the same extent. 3 Nadolol caused a greater bradycardia both at rest and during exercise than did atenolol, thereby effecting a greater reduction in double-product. 4 During progressive treadmill exercise neither atenolol nor nadolol prevented a linear increase in heart rate and blood pressure which were parallel to, but at a lower level than, that produced by placebo. 5 In each individual patient the magnitude of the hypotensive effect produced by one drug was similar to that produced by the other. 6 All the treatment periods resulted in the same linear increase in the patients' perceived exertion scores during exercise despite marked differences in haemodynamic responses evoked by the beta-adrenoceptor blockers compared with placebo. 7 Neither atenolol or nadolol produced any significant change in peak expiratory flow rate compared with placebo.

Preserved renal perfusion during treatment of essential hypertension with the beta blocker nadolol

Several beta-adrenergic antagonists impair renal perfusion during treatment of hypertension in man. The acute and chronic effects of a new noncardioselective beta blocker, nadolol, on renal hemodynamics, intravascular volume, and renal electrolyte excretion were studied in 10 men with essential hypertension. Oral nadolol normalized systemic blood pressure without impairment of glomerular filtration rate or renal blood flow, indicating preserved renal blood flow and glomerular filtration rate autoregulation. Intravascular volume and renal excretion of electrolytes were similarly unaltered. Once-daily nadolol lowers blood pressure without renal hemodynamic of functional embarrassment.

Cardiac arrhythmias induced by guanethidine in cats anesthetized with halothane

Rapid i.v. administration of guanethidine provokes severe and sustained ventricular arrhythmias in cats anesthetized with halothane. The arrhythmias include premature ventricular excitations, multifocal ventricular rhythm, bigeminy, trigeminy and ventricular tachycardia. They begin in about 20 sec and last from 4 to 100 min. By comparison, a standard dose of noradrenaline (10 micrograms/kg) induces ventricular arrhythmias which develop in about 12 sec and continue for 1-2.5 min. Pretreatment with beta-adrenoceptor blocking drugs prevents arrhythmias from both drugs, and pretreatment with imipramine or reserpine prevents arrhythmias for guanethidine but not noradrenaline. The adrenergic neuron blocking action of guanethidine does not alter the arrhythmogenic action of guanethidine since arrhythmias can still be produced after adrenergic neuron blockade. These results indicate that guanethidine causes arrhythmias by releasing noradrenaline from cardiac adrenergic neuron storage sites and, therefore, point out the vulnerability of the heart to arrhythmias when noradrenaline-releasing drugs interact with halogenated hydrocarbon anesthetics.

Determination of serum nadolol levels by GLC--selected ion monitoring mass spectrometry: comparison with a spectrofluorometric method

A method to determine the serum concentration of the beta-adrenergic receptor blocking agent, nadolol, by GLC--selected ion monitoring mass spectrometry of the tri(trimethysilyl) ether derivative is described. A basic solution of serum was extracted, known amounts of internal standard were added to the extract, and the extract was back-extracted into acidic media and lyophilized. The resulting solids were reacted with N-trimethylsilylimidazole. Coded serum samples of 12 subjects, given nadolol alone or in combination with a second drug, were analyzed. The ions at m/e 86 and 100 were monitored to establish the relative concentration ratio of nadolol and the internal reference N-methylnadolol. No interferences from blood components or other administered drugs were observed. A detection level of 6.95 ng/ml of serum was found.

Fluorometric determination of nadolol in human serum and urine

To determine nadolol, a new beta-adrenergic blocking agent, in serum and urine, the drug is extracted into n-butyl acetate or ether from alkaline potassium chloride saturated samples. After back-extraction into 0.1 N HCl, the drug is oxidized with periodic acid; the resulting aldehyde is coupled with o-phenylenediamine to produce a fluorescent compound. The method can measure as little as 0.01 microgram of nadolol/sample.

Metabolic studies in patients with nadolol: oral and intravenous administration

Nadolol-14C, 2,3-cis-5-(3-[(1,1-dimethylethyl)amino]-2-hydroxypropoxy)-1,2,3,4-tetrahydro-2,3-naphthalenediol, a nonselective beta-adrenergic blocking agent, was administered orally and intravenously at 2-mg doses to patients with mild cases of essential hypertension. Terminal plasma half-times after oral and intravenous doses were an average of 12.2 and 9.8 hours, respectively. After oral doses, an average of 24.6 and 76.9 per cent of the dose was excreted in urine and feces, respectively, whereas, after intravenous doses, an average of 72.9 and 23.3 per cent of the dose was excreted by the same routes. Calculations of absorption, based on urinary excretion and on areas under the plasma concentration-versus-time curves, indicated that oral doses of nadolol-14C were absorbed to the extent of 33.6+/-2.4 per cent (+/- S.E.). The average overall volume of distribution after intravenous administration was 2.09+/-0.51 1./kg (+/- S.E.), and the average volume of the central compartment was 0.30+/-0.04 1./kg. Only unchanged nadolol-14C was excreted in the urine and feces of patients after either oral or intravenous administration of the drug.