Carvedilol in the treatment of hypertension--a review of the clinical data base

Octopamine drives honeybee thermogenesis

In times of environmental change species have two options to survive: they either relocate to a new habitat or they adapt to the altered environment. Adaptation requires physiological plasticity and provides a selection benefit. In this regard, the Western honeybee (Apis mellifera) protrudes with its thermoregulatory capabilities, which enables a nearly worldwide distribution. Especially in the cold, shivering thermogenesis enables foraging as well as proper brood development and thus survival. In this study, we present octopamine signaling as a neurochemical prerequisite for honeybee thermogenesis: we were able to induce hypothermia by depleting octopamine in the flight muscles. Additionally, we could restore the ability to increase body temperature by administering octopamine. Thus, we conclude that octopamine signaling in the flight muscles is necessary for thermogenesis. Moreover, we show that these effects are mediated by β octopamine receptors. The significance of our results is highlighted by the fact the respective receptor genes underlie enormous selective pressure due to adaptation to cold climates. Finally, octopamine signaling in the service of thermogenesis might be a key strategy to survive in a changing environment.

Development and evaluation of a physiologically based pharmacokinetic model to predict carvedilol-paroxetine metabolic drug-drug interaction in healthy adults and its extrapolation to virtual chronic heart failure patients for dose optimization

Purpose: The metabolic drug-drug interactions (mDDIs) are one of the most important challenges faced by the pharmaceutical industry during the drug development stage and are frequently associated with labeling restrictions and withdrawal of drugs. The capacity of physiologically based pharmacokinetic (PBPK) models to absorb and upgrade with the newly available information on drug and population-specific parameters, makes them a preferred choice over the conventional pharmacokinetic models for predicting mDDIs.Method: A PBPK model capable of predicting the stereo-selective disposition of carvedilol after administering paroxetine by incorporating mechanism (time) based inhibition of CYP2D6 and CYP3A4 was developed by using the population-based absorption, distribution, metabolism and elimination (ADME) simulator, Simcyp®.Results: The model predictions for both carvedilol enantiomers were in close agreement with the observed PK data, as the ratios for observed/predicted PK parameters were within the 2-fold error range. The developed PBPK model was successful in capturing an increase in exposures of R and S-carvedilol, due to the time-based inhibition of CYP2D6 enzyme caused by paroxetine.Conclusion: The developed model can be used for exploring complex clinical scenarios, where multiple drugs are given concurrently, particularly in diseased populations where no clinical trial data is available.

Left ventricular hypertrophy: major risk factor in patients with hypertension: update and practical clinical applications

Left ventricular hypertrophy is a maladaptive response to chronic pressure overload and an important risk factor for atrial fibrillation, diastolic heart failure, systolic heart failure, and sudden death in patients with hypertension. Since not all patients with hypertension develop left ventricular hypertrophy, there are clinical findings that should be kept in mind that may alert the physician to the presence of left ventricular hypertrophy so a more definitive evaluation can be performed using an echocardiogram or cardiovascular magnetic resonance. Controlling arterial pressure, sodium restriction, and weight loss independently facilitate the regression of left ventricular hypertrophy. Choice of antihypertensive agents may be important when treating a patient with hypertensive left ventricular hypertrophy. Angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers followed by calcium channel antagonists most rapidly facilitate the regression of left ventricular hypertrophy. With the regression of left ventricular hypertrophy, diastolic function and coronary flow reserve usually improve, and cardiovascular risk decreases.

Carvedilol increases blood pressure response to phenylephrine infusion in heart failure subjects with systolic dysfunction: evidence of improved vascular alpha1-adrenoreceptor signal transduction

INTRODUCTION

Alpha(1)-adrenergic receptor (alpha(1)-AR) stimulation produces smooth muscle contraction, vasoconstriction, and myocyte hypertrophy, suggesting a potential therapeutic role for alpha(1)-AR antagonists to reduce cardiac workload and myocardial hypertrophy. Preliminary reports suggest that vascular alpha(1)-ARs are desensitized in heart failure (HF) in a manner similar to myocardial beta(1)-ARs. We examined alpha(1)-AR signal transduction by repeat phenylephrine (PE) infusions in patients with HF receiving chronic carvedilol therapy.

METHODS

Twelve subjects with HF not currently receiving beta-blockers were up-titrated to maximum tolerable doses of carvedilol. Subjects underwent alpha(1)-AR stimulation testing at study baseline, 2 weeks after each dose titration, and 6 months after maintenance of maximum carvedilol dose. Phenylephrine infusions began at 0.5 microg kg(-1) min(-1), with dose titrations every 10 minutes, to a maximum of 5 microg kg(-1) min(-1). Phenylephrine dose response was evaluated by the PE rate required to elicit a 20 mm Hg increase in systolic blood pressure (BP), designated PS(20).

RESULTS

All doses of carvedilol significantly reduced preinfusion measures of heart rate, systolic BP, diastolic BP, and mean arterial pressure. However, carvedilol also produced a paradoxical trend toward PS(20) reduction (indicating increased PE response) that reached significance at the completion of carvedilol dose titration (PS(20) ratio vs baseline = 0.78; P < .001). All effects were maintained over a 6-month treatment period with no evidence of tolerance.

CONCLUSIONS

Increasing BP response to PE infusion suggests improvement in vascular alpha(1)-AR signal transduction with chronic carvedilol therapy. This effect is evident despite no detectable tolerance to preinfusion BP reductions. The varying affinities of alpha(1)-AR subtypes for carvedilol and PE may have contributed to this finding.

Metabolic Properties of Vasodilating β Blockers: Management Considerations for Hypertensive Diabetic Patients and Patients With the Metabolic Syndrome

Type 2 diabetes and hypertension are both insulin-resistant states that impose an excessive risk burden for future major cardiovascular events, including coronary heart disease, stroke, and heart failure. beta-adrenergic receptor antagonists are effective for the treatment of hypertension, but they are underused in diabetic patients because of possible adverse effects on carbohydrate and lipid metabolism, including insulin resistance, glucose intolerance, and dyslipidemia. Traditional beta blockers, both nonselective and selective, are vasoconstrictive due to unopposed alpha1 activity; however, vasodilating beta blockers are not associated with these negative metabolic effects. This review discusses the background of insulin resistance and its link to diabetes and hypertension, emphasizing the role of vascular control by the renin-angiotensin and sympathetic nervous systems on insulin sensitivity and glucose utilization. Clinical evidence is reviewed for the use of vasodilating beta blockers in the treatment of hypertension and in reducing cardiovascular risk in the diabetic population.

Carvedilol in children with cardiomyopathy: 3-year experience at a single institution

BACKGROUND

Carvedilol reduces mortality and hospitalization in adults with congestive heart failure. Limited information is available about its use in children.

METHODS

We reviewed the medical records of 24 children with dilated cardiomyopathy and left ventricular ejection fraction of <or=40%, who were treated with carvedilol as adjunct therapy to angiotensin-converting enzyme inhibitors, digoxin and diuretics.

RESULTS

Carvedilol was initiated 14.3 +/- 23.3 (mean +/- SD) months after the diagnosis of cardiomyopathy. Mean age at initiation of therapy was 7.2 +/- 6.4 years. The mean initial and maximum doses were 0.15 +/- 0.09 and 0.98 +/- 0.26 mg/kg/day. Adverse effects occurred in 5 patients (21%). Two patients (8%) required discontinuation of the drug within 5 weeks of the initial dose. The remaining 22 patients tolerated carvedilol for a mean follow-up period of 26.6 +/- 14.7 months. Among these 22 patients, mean left ventricular ejection fraction improved from 24.6 +/- 7.6% to 42.2 +/- 14.2% (p < 0.001), and mean sphericity index from 0.86 +/- 0.11 to 0.74 +/- 0.10 (p < 0.001). New York Heart Association functional class improved in 15 patients (68%). One patient (4%) died and 3 (14%) were transplanted.

CONCLUSIONS

Carvedilol, in addition to standard therapy for dilated cardiomyopathy in children improves cardiac function and symptoms; it is well tolerated, with minimal adverse effects, but close monitoring is necessary as it might worsen congestive heart failure and precipitate asthma. Control studies are necessary to assess the effect of carvedilol on mortality and hospitalization rates.