Clinical relevance of pharmacokinetic differences between beta blockers.

Fundamental differences in the pharmacodynamic and pharmacokinetic profiles of beta-adrenergic blocking agents must be considered in optimizing their efficacy and determining the appropriate selection of these drugs in different patients. Beta blockers are contraindicated in patients with asthma and should be used cautiously in heart failure. Clinically important distinctions are related to whether a beta blocker is beta1-selective or nonselective. Most adverse effects of beta-blocker use are related to interference with beta2-mediated functions including bronchodilation, vasodilation, and mobilization of free fatty acids. To achieve the potential benefits of beta1 blockade (decreased heart rate, blood pressure, cardiac workload, and excitability), a low plasma concentration of a beta1-selective drug is required. Adverse effects of beta blockers can be further decreased by selecting a sustained-release beta1-selective drug. Beta blockers are further differentiated on the basis of lipophilicity or hydrophilicity. Lipophilic beta blockers cross the blood-brain barrier, whereas hydrophilic agents do not enter the central nervous system. Some lipophilic agents (metroprolol, timolol, and propanolol) have been shown to decrease mortality in coronary heart disease, particularly sudden cardiac death.