Exercise increases plasma concentrations of (R)- and (S)-propranolol

Simulation of differential drug pharmacokinetics under heat and exercise stress using a physiologically based pharmacokinetic modeling approach

Under extreme conditions of heat exposure and exercise stress, the human body undergoes major physiological changes. Perturbations in organ blood flows, gastrointestinal properties, and vascular physiology may impact the body's ability to absorb, distribute, and eliminate drugs. Clinical studies on the effect of these stressors on drug pharmacokinetics demonstrate that the likelihood of pharmacokinetic alteration is dependent on drug properties and the intensity of the stressor. The objectives of this study were to use literature data to quantify the correlation between exercise and heat exposure intensity to changing physiological parameters and further, to use this information for the parameterization of a whole-body, physiologically based pharmacokinetic model for the purposes of determining those drug properties most likely to demonstrate altered drug pharmacokinetics under stress. Cardiac output and most organ blood flows were correlated with heart rate using regression analysis. Other altered parameters included hematocrit and intravascular albumin concentration. Pharmacokinetic simulations of intravenous and oral administration of hypothetical drugs with either a low or high value of lipophilicity, unbound fraction in plasma, and unbound intrinsic hepatic clearance demonstrated that the area under the curve of those drugs with a high unbound intrinsic clearance was most affected (up to a 130% increase) following intravenous administration, whereas following oral administration, pharmacokinetic changes were smaller (<40% increase in area under the curve) for all hypothetical compounds. A midazolam physiologically based pharmacokinetic model was also used to demonstrate that simulated changes in pharmacokinetic parameters under exercise and heat stress were generally consistent with those reported in the literature.

The effects of high physical activity on pharmacokinetic drug interactions

INTRODUCTION

With the development of new drugs, it is common practice for drug manufacturers to measure their pharmacokinetic parameters. This testing involves the discovery of the absorption, distribution, metabolic, excretory and toxicological properties of drugs. The testing is usually done in non-stressful conditions at rest, however, this does not necessarily tell the entire picture as there is increasing knowledge about the effects that high levels of physical activity can have on the pharmacokinetics of some medications.

AREAS COVERED

This review discusses the alterations that physical activity can have on the absorption, distribution, metabolism and elimination parameters of commonly used medications, and clinical outcomes data are reported when known, demonstrating that an interaction exists between exercise and certain medications. This drug-exercise pharmacokinetic interaction alters the performance of medications especially under conditions where exercise is performed for a long period of time. Particular medications that may be affected are those with a narrow therapeutic dosing range, such as digoxin, theophylline and warfarin. Other important medications include insulin and those administered via a transdermal patch drug delivery system. For this review, a literature search was performed between 1966 and 2010.

EXPERT OPINION

Patients and healthcare providers should be aware that exercise can adversely affect the way some medications are intended to work. Patients taking certain medications should be closely monitored when performing high amounts of physical activity.

Comparing Beta-Blocking Effects of Bisoprolol, Carvedilol and Nebivolol

OBJECTIVE

Bisoprolol, carvedilol and nebivolol have been shown to be effective in the treatment of heart failure. However, the beta-blocking effects of these drugs have never been compared directly.

METHODS

Therefore, we performed a randomized, double-blind, placebo-controlled, cross-over trial in 16 healthy males. Subjects received 10 mg bisoprolol, 50 mg carvedilol, 10 mg nebivolol and placebo on the first morning followed by 5 mg bisoprolol once daily, 25 mg carvedilol twice daily, 5 mg nebivolol once daily and placebo for 1 week. Heart rate and blood pressure were measured at rest and exercise 3 and 24 h following intake of the first dose, and immediately before and 3 hours following intake of the last dose of each drug. In addition, effects of the drugs on nocturnal melatonin release were determined, and quality of life (QOL) was evaluated.

RESULTS

Heart rate at exercise was decreased at 3 h following intake of the first single dose of each drug by bisoprolol (-24%), carvedilol (-17%) and nebivolol (-15%), and at 24 h following intake of the respective last dose of each drug following 1 week of chronic administration by bisoprolol (-14%), carvedilol (12 h; -15%) and nebivolol (-13%) (p < 0.05 in all cases). Thus, trough-to-peak-ratios at long-term were as follows: Bisoprolol, 58%; carvedilol (12 h), 85%; nebivolol, 91%. Nocturnal melatonin release was decreased by bisoprolol (-44%, p < 0.05) whereas nebivolol and carvedilol had no effect. QOL with carvedilol was slightly but significantly lower than with the other drugs, whereas bisoprolol and nebivolol did not alter QOL.

CONCLUSIONS

These data show that peak beta-blocking effects of bisoprolol appear stronger than those of nebivolol and carvedilol. On the other hand, nebivolol exerts the highest trough-to-peak-ratio. However, beta-blocking effects of all the three drugs are similar at trough. Only bisoprolol but neither nebivolol nor carvedilol decreased nocturnal melatonin release, a feature which might cause sleep disturbances. Finally, only carvedilol slightly decreased QOL, whereas nebivolol and bisoprolol did not affect QOL. We conclude that different beta-blockers may exert clinically relevant different effects.

Unpredicted lack of effect of exercise on plasma concentrations of carvedilol

In vitro studies have shown that beta-blockers are taken up into and released from adrenergic cells together with epinephrine and norepinephrine. Consequently, studies in humans revealed an increase in plasma concentrations of propranolol and atenolol during physical exercise. However, carvedilol has not been investigated in a similar fashion. Eleven hypertensive patients on long-term treatment (4 months) with carvedilol followed an exercise regimen. Plasma concentrations of carvedilol were determined at rest (9.7 +/- 3.4 ng/ml), during exercise (9.0 +/- 3.2 ng/ml), and after 15 min of recovery (9.1 +/- 2.7 ng/ml). Contrary to predictions, exercise had no effect on plasma concentrations of carvedilol, a finding that is in contrast to other beta-blockers. We conclude that carvedilol is not taken up into and released from adrenergic nerves during exercise, a feature that clearly distinguishes carvedilol from all other beta-adrenergic antagonists so far investigated.