Effect of exercise on renal clearance of atenolol

Critical Analysis of Hepatic Clearance Based on an Advection Mass Transfer Model and Mass Balance

The relationship between liver blood flow rate and hepatic clearance has been derived and validated based on the constitutive principle of mass conservation using an advective mass transfer model for bivariate concentration, C_i (x, t). Metabolic elimination continuously diminishes along the blood flow path line, corresponding with the concentration gradient. Because of the constraint introduced by constant blood velocity, x and t are not independent variables. This requires the introduction of a new factor called the dwell time, which accounts for the time a drug is retained in the liver. First-order or saturable drug metabolism is dependent on perfusate drug concentration and the dwell time. A new extraction factor is explicitly identified as E = ln C_in/C_out. Because the isolated organ perfusion model described here is validated, it provides a basis for drawing inferences and exploring underlying features, mechanisms, and principles on which this model is based. In the conventional model, these underlying constitutive principles are unavailable. The concentration-time profile of a physiological-based elimination network is found to be inconsistent with the profile described by a pharmacokinetic model. For this reason, among others discussed, physiological-based models are incompatible with pharmacokinetic models and therefore cannot be used to explain systemic pharmacokinetic behavior.

Transdermal patch drug delivery interactions with exercise

Transdermal drug delivery systems, such as the transdermal patch, continue to be a popular and convenient way to administer medications. There are currently several medications that use a transdermal patch drug delivery system. This article describes the potential untoward side effects of increased drug absorption through the use of a transdermal patch in individuals who exercise or participate in sporting events. Four studies have been reported that demonstrate a significant increase in the plasma concentration of nitroglycerin when individuals exercise compared with rest. Likewise, several case reports and two studies have been conducted that demonstrate nicotine toxicity and increased plasma nicotine while wearing a nicotine patch in individuals who exercise or participate in sporting events compared with rest. Healthcare providers, trainers and coaches should be aware of proper transdermal patch use, especially while exercising, in order to provide needed information to their respective patients and athletes to avoid potential untoward side effects. Particular caution should be given to individuals who participate in an extreme sporting event of long duration. Further research that includes more medications is needed in this area.

Potential interactions between exercise and drug therapy

Certain physiological changes caused by aerobic exercise can alter the pharmacokinetics of some drugs. A systematic review of the pharmacokinetic changes that can affect drugs as a result of aerobic exercise is provided. Eleven commonly used drugs are reviewed for their potential interaction with exercising patients. Serum concentrations of two beta-blocking agents, atenolol and propranolol, and one antibiotic, doxycycline, have shown to increase as a result of exercise. No pharmacokinetic changes have been found in exercising patients taking carvedilol or verapamil. Patients who exercise after taking digoxin experience a decreased digoxin serum concentration with an increased skeletal muscle concentration. The clearance of theophylline has been shown to decrease resulting in an increase in plasma half-life during exercise. The risk of hypoglycaemia may increase when patients with diabetes mellitus inject insulin into a muscle just prior to exercising that muscle. Increasing physical activity in patients taking warfarin has been shown to decrease the international normalised ratio. Much is still unknown regarding the interactions that exist between exercise and drug therapy. More studies need to be completed in this area before definite conclusions are made and clinical relevance can be established. Clinicians should be aware that the potential for such interactions exists, especially for drugs with a narrow therapeutic range and in patients who participate in extreme sporting activities.

Comparison of the effects of prizidilol and propranolol on renal haemodynamics at rest and during exercise

Effective renal plasma flow and glomerular filtration rate were measured in 22 mild-to-moderate, uncomplicated, essential hypertensive patients during placebo and after 3 months of randomly assigned treatment either with prizidilol (n = 10) or propranolol (n = 12). Measurements were performed at rest and during cycloergometer exercise. For a comparable effect on blood pressure effective renal plasma flow was significantly increased at rest by prizidilol (+9%) and decreased by propranolol (-13.6%); these patterns were maintained during exercise. Glomerular filtration rate was immodified after the treatment with both drugs. It is concluded that prizidilol is an effective hypotensive agent with no deleterious effects on renal haemodynamics.

Exercise-induced increments in plasma levels of propranolol and noradrenaline

Exercise-induced changes in the plasma levels of propranolol and noradrenaline were determined in nine volunteers. Total plasma propranolol levels were increased during submaximal treadmill exercise, with exercise-induced increments of 13 +/- 4% at 4 h after the last dose, 18 +/- 7% at 9 h and 41 +/- 5% at 16 h. Exercise-induced increments in plasma propranolol were observed after single as well as repeated doses. During exercise, increments in plasma propranolol were correlated temporally with changes in plasma noradrenaline. Exercise-induced increments in plasma noradrenaline were greater during propranolol administration than during placebo periods. The changes in plasma propranolol concentration during exercise may reflect a redistribution of propranolol at its site(s) of action.

Metabolic aspects of maximal exercise performance after slow release metoprolol and after atenolol

Maximal exercise performance by eight healthy male subjects was tested after one week of medication with slow-release metoprolol 200 mg/d (metoprolol-SR), atenolol 200 mg/d or placebo, in a double blind crossover trial. The maximal working capacity was significantly decreased after atenolol and metoprolol-SR. Plasma glucose and FFA concentrations during the exercise test did not change: either after placebo therapy or after beta-blockade. The anerobic threshold did not change after beta-blockade, but the changes in lactate due to the exercise were less after beta-blockade. Neither beta-blocker affected the exercise-induced alteration in airway resistance. Both drugs caused a small but significant ventilatory depression at rest and at 75% of maximal exercise. It is concluded that the limiting factor in maximal exercise performance after beta 1-adrenergic blockade does not lie in oxygen transport to the working muscles via ventilation and the circulation, but is most probably due to anaerobic metabolism.