RELATIONS BETWEEN AGE AND WEIGHT AND DOSAGE OF DRUGS

Abstract

The effective, usually lethal, doses of various drugs are usually less per kg. in the larger animals of a sp. than in the smaller. This is an over-simplification; a sp. may show either high resistance or high susceptibility at birth, with possible decrease for a few days or wks., followed by increase. On the basis of clinical observation the therapeutic dosage of atropine, the arsphenamines, bismuth, digitalis, mandelic acid, some mercurials, sulfanil-amide and some other drugs, is set at somewhat higher levels in proportion to wt. for infants and children than for adults. Dosage of morphine or strychnine, even in direct proportion to body wt., appears too great for safety of some individuals, and caution is in order until susceptibility is detd., especially in the case of an infant, child or aged person. The greater tolerance of the young for some drugs may be due to various factors, possibly including proportionately larger avg. surface area, basal metabolic rate, liver wt., daily urinary vol. The inevitable excretory and metabolic readjustments in the 1st few days or wks. of extrauterine life, as well as the decline in metabolic rate, reduction in size and possible pathological changes in liver and kidney after middle life (especially in old age) enjoin caution in the use of drugs during these periods. Charts show the relative doses provided by various rules based on age, wt. to various powers, surface area, and basal caloric output.