.. Figure 4. Mean (±SE) values of chlordiazepoxide elimination half-life (left) and clearance (right) in young and elderly male volunteers as determined in the study described in Figure 3 59. The Obeticholic Acid datasheet asterisk (*) indicates a statistically significant difference … In addition to changes in specific organs, such as the kidney and the liver,
more general changes in body habitus also take place. There is an overall increase in adipose tissue, which leads to an increased volume of distribution for lipophilic drugs. Gender is an important, factor, since women have a greater proportion of adipose tissue than men, regardless of age. Such changes do not affect absolute drug accumulation, Inhibitors,research,lifescience,medical but, they do affect elimination half-life, which means that the time until a steadystate situation is reached will be increased. Inhibitors,research,lifescience,medical Consequently, the time from the initiation of drug therapy or dosage change until the plasma levels have arrived at the new higher (or lower) steady -state will be prolonged. Time to desired clinical effect can also be expected to be prolonged. Furthermore, when a given medication effect (such as a sign of toxicity) occurs later than expected, it may lead to the erroneous conclusion
that, it, is not medication-related, since the patient was already considered (erroneously) to be “stabilized” on a particular medication. Inhibitors,research,lifescience,medical Given that the majority of the aged are female, substantial differences in volumes of distribution can be expected.
For drugs whose initial pharmacokinetic profiles have been determined Inhibitors,research,lifescience,medical in younger, predominantly male populations,62 the differences between actual and expected half-lives could be striking. For lipophilic drugs that require renal excretion or hepatic oxidation, the combination of reduced clearance and increased volume of distribution will lead Inhibitors,research,lifescience,medical to profound increases in half-life. The familiar adage, “start low, go slow,” suggesting lower starting doses with slower and smaller incremental changes, becomes almost a clinical imperative. Frequently implicated medications A number of medications seem to have a predictable potential for causing cognitive toxicity in aging individuals. Often this information is clearly presented in the drug’s product labeling.63 This should not be misconstrued to mean that these medications already are never appropriate for use in aging people. Close management, with consideration of the specific patient, and clinical circumstances and particular risk-benefit balance may result in efficacy with minimal or acceptable side effects. Generally, drugs that are predominantly used in older populations will reveal any toxicities in that same population. It may not be clear whether older individuals are at greater risk. Medications that arc used in all age-groups seem to be more likely to have been studied with regard to whether the elderly are more likely to develop these toxicities.
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