Physiological Alterations with Aging

Table 2.1 Physiological alterations with aging that may affect pharmacotherapy... 

Some healthy elderly may not be very affected by pharmacological alterations whereas others have become very susceptible to adverse effects of drugs. It is especially important for elderly patients that pharmacotherapy is individualised. With knowledge of expected physiologic changes with aging, decisions should be based on the individual patient s disease and concomitant medications. 

Elderly patients in moderate to severe pain may require narcotic analgesics, but the use of opioids can be associated with significant toxicity because of the unique metabolic and physiologic alterations in aging patients. 

B. Dosing Considerations Determined by Alterations in Physiology with Aging... 

The restoration of immune functions of the aged individuals is possible and might be beneficial for them to cope with various diseases associated with aging (Hirokawa, 1997). Physiological thymic atrophy is controlled by both extrathymic and intrathymic factors and is not a totally irreversible process. Tlie process of thymic atrophy might be explained by a further understanding of the relationship between the neuroendocrine and the immune systems (Hirokawa et al., 1994). Although the most obvious age-related structural alteration of the immune system occurs in the thymus, the role of thymic involution in immunosenescence is still not well understood. 

The effect of age on percutaneous absorption has been examined in vivo in man with variable results. It was postulated (Roskos et al. 1989) that reduced hydration levels and lipid content of older skin may be responsible for a demonstrated reduction in skin permeability where the permeants were hydrophilic in nature (no reduction was seen for model hydrophobic compounds) (Table 14.2). The reduced absorption of benzoic acid demonstrated in the elderly (Rougier 1991) was in line with this suggestion, but not the reduction in absorption of testosterone (lipophilic) (Roskos et al. 1986), or lack of change in the absorption of methyl nicotinate (more hydrophilic) with age (Guy et al. 1983). There are a number of potential physiological changes which may be responsible for age-related alterations, including an increase in the size of individual stratum corneum corneocytes, increased dehydration of the outer layers of the stratum corneum with age, decreased epidermal turnover and decreased microvascular clearance (reviewed in Roskos and Maibach 1992). The issue of age-related variability, however, is far from resolved. 

The so-called normal range of blood and serum vitamin levels is always derived from observations on healthy young subjects. How about a comparison with healthy old subjects, whose percentage in the population is steadily increasing Much may be learned about the cause of the decrease of physiological function and of the increased susceptibility to organic disease in old age, if the role of vitamins as parameter of these alterations were investigated with a view to preventive theory. 

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