The following rule of Young is sufficiently accurate for most drugs:
Add 12 to the age and divide by the age to get the denominator of the
fraction, the numerator of which is 1. Thus, for a child of two years,
2 + 12
——— = 7, and the dose is ⅐ of that for an adult.
2
For children up to twelve months of age, Young’s rule may be worked
out as follows: Add 144 to the age in months, which sum becomes the
denominator of the fraction, the numerator of which is the child’s age.
Thus, for a baby of eight months,
8 8
——— = ——, or ¹/₁₉ of an adult’s dose;
8 + 144 152
for a baby of six months,
6 6
——— = ——, or ¹/₂₅ of an adult’s dose.
6 + 144 150
The following table, based on Young’s rule, is sufficiently accurate
in ordinary cases, and its use will avoid the necessity of mathematic
calculations on the part of the physician:
Child aged one month ¹/₁₄₅ of an adult’s dose.
“ “ two months ¹/₇₃ “ “ “
“ “ three months ¹/₄₉ “ “ “
“ “ four months ¹/₃₇ “ “ “
“ “ five months ¹/₃₀ “ “ “
“ “ six months ¹/₂₅ “ “ “
“ “ seven months ¹/₂₂ “ “ “
“ “ eight months ¹/₁₉ “ “ “
“ “ nine months ¹/₁₇ “ “ “
“ “ ten months ¹/₁₅ “ “ “
“ “ eleven months ¹/₁₄ “ “ “
“ “ twelve months ¹/₁₃ “ “ “
“ “ two years ¹/₇ “ “ “
“ “ three years ¹/₅ “ “ “
“ “ four years ¹/₄ “ “ “
“ “ five years ⁵/₁₇ “ “ “
“ “ six years ¹/₃ “ “ “
“ “ seven years ⁷/₁₉ “ “ “
“ “ eight years ²/₃ “ “ “
“ “ nine years ³/₇ “ “ “
“ “ ten years ⁵/₁₁ “ “ “
“ “ eleven years ¹/₂ “ “ “
“ “ twelve years ¹/₂ “ “ “
Of powerful narcotics, such as opium, scarcely more than one-half
of this proportion should be used. In the case of mild cathartics,
however, two or even three times this proportion may be given.