Why the study?
Does the lipophilicity of beta-blockers affect their ability to cross the blood-brain barrier and enter brain tissue in neurosurgical patients?
Does the lipophilicity of beta-blockers affect their ability to cross the blood-brain barrier and enter brain tissue in neurosurgical patients?
Lipophilic beta-blockers accumulate in brain tissue at significantly higher concentrations than hydrophilic atenolol, providing a pharmacokinetic basis for differences in CNS side effects.
1 This study on 21 neurosurgical patients was set up to investigate the extent to which four chronically administered beta-adrenoceptor blockers, propranolol, oxprenolol, metoprolol and atenolol, cross and blood-brain barrier and enter the cerebrospinal fluid (CSF) and brain tissue. The concentration in the CSF of the three lipophilic beta-adrenoceptor blockers, propranolol, oxprenolol and metoprolol, approximated to the free drug concentration in the plasma, and was a poor predictor of brain concentration. These three lipophilic beta-adrenoceptor blockers appeared in brain tissue at concentrations 10-20 times greater than that of hydrophilic atenolol. The approximate brain/plasma ratio for propranolol was 26, for oxprenolol 50, for metoprolol 12 and for atenolol 0.2. 2 The low concentration of atenolol in brain tissue is possibly responsible for the low incidence of central nervous system-related side effects in patients on this agent compared to lipophilic beta-adrenoceptor blockers.
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Neil‐Dwyer et al. (1981) studied this question.
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