A) Age
Sensitivity to drugs changes with age. That is why so-called perinatal pharmacology that studies specificities of drug effect on the fetus (from 24 weeks of pregnancy up until delivery) and on the newborn (up to 4 weeks of life) is distinguished. With regard to drug sensitivity, a fetus in the last trimester and newborns in the first month of life are significantly different from adults. This is mainly due to the insufficiency of most enzymes, renal func-
tion, increased permeability of the blood-brain barrier and the underdevelopment of the CNS. During this period of life, receptors have different sensitivity to drugs. For example, newborns are more susceptible to some drugs, affecting the CNS (in particular to morphine). Chloramphenicol is very toxic for them and may even cause death. This occurs due to the fact that the liver lacks the necessary enzymes for its detoxification. At an early age children can not be prescribed drugs that intensify secretory activity of the glands (bronchial, nasal mucosa, other), because it can disturb respiration and be a cause of respiratory disease.
The field of pharmacology, studying specificities of drug effects on child's organism, is called pediatric pharmacology.
In elderly and old patients drug absorption is delayed, their metabolism is less effective, drugs elimination via kidneys is reduced. In general, sensitivity to most drugs in elderly and old patients is increased, and therefore the doses should be reduced. Besides minimally toxic drugs should be selected for use in this population.
It is important to know specificities of drug effect in elderly and old patients (socalled geriatric1 pharmacology) because the proportion of these age groups among the general population has significantly increased.