In an older person, the binding to albumin in the blood stream may decrease to 94 percent. Consequently, the amount of unbound, active drug could double. Decrease in Liver Function Metabolism, or the chemical detoxification of a drug, takes place in the liver. Some drugs are changed into water-soluble form so they can be excreted from the body. With aging, the liver decreases in size, blood flow decreases, and the enzymes that break down drugs declines.
Drugs can accumulate, causing toxicity unless the dosage is reduced.
Decrease in Kidney Function Changes in the kidney are more dramatic than those in any other organ. The kidneys become smaller, blood flow decreases, and filtering capacity decreases. Between the ages of 20 and 80 there is an average decline of 35 percent in kidney function. Medical conditions such as heart failure, anemia, or dehydration may further impair kidney function. Certain drugs are excreted more slowly and, thus, can remain active longer in the body.