Antibiotics in the elderly: Age-related changes in the liver and kidneys contribute to changes in biotransformation and the elimination of many drugs. This may be the reason for the development of side effects of drugs that are usually safe and non-toxic. Atrophic processes in the gastrointestinal mucosa lead to changes in the absorption of certain drugs, which explains the low effectiveness of therapy.
With age, as a result of weight loss and muscle atrophy, the water content in the body decreases (by 10-15%) and the relative weight of adipose tissue increases (in men from 18 to 36%, in women from 33 to 48%). Consequently, in the elderly, the volume of distribution of water-soluble drugs changes, which is accompanied by a certain increase in their concentration in the blood. The volume of distribution of fat-soluble drugs in the elderly increases.
A decrease in the penetration of drugs into the tissues as a result of a decrease in the volume of distribution and the level of tissue blood flow may be one of the reasons for the insufficient clinical and bacteriological effectiveness of antibiotics in elderly patients.
The level of drug metabolism in the liver decreases with age as a result of a decrease in liver mass (after 40 years by 1% per year), hepatic blood flow (from 25 to 65 years by 40-45%) and the activity of microsomal enzymes. This leads to a decrease in the level of presystemic metabolism and phase I metabolism of medicinal drugs in the liver. As a result, the clearance decreases and the serum concentration of those antibacterial drugs that are mainly metabolized (more than 50%) in the liver increases: cefoperazone, doxycycline, lincomycin, clindamycin, chloramphenicol, pefloxacin, macrolides, rifamgscin, etc.
The elimination of most antibiotics is carried out by the kidneys. With age, as a result of atrophy of the cortical layer of the kidneys, the level of glomerular filtration decreases (from 20 to 50 years by 0.4 ml/min per year, after 50 years — by 1 ml/min per year) and tubular secretion (on average by 7% every 10 years). This is accompanied by a slowdown in the excretion of many drugs in elderly patients, which leads to an increase in their concentration in the blood.
In this regard, it is desirable to adjust the administered doses of antibacterial drugs that have a predominantly renal elimination pathway, in accordance with the value of glomerular filtration. This is especially important for potentially toxic drugs: aminoglycosides, vancomycin, carbenicillin, ticarcillin, tetracyclines, clomiphene, polymyxins, etc.
When deciding on the choice of an antibiotic, it is necessary to consider the features of drug interaction, since many elderly patients simultaneously take several drugs from different groups (hypotensive, antianginal, nootropic, etc.).