Doses—Variation at Different Ages.
From 20 to 45 years adult doses are given; 50 years ⅚; 60 years ⅘; 80 years ⅔ of adult doses.
Doses for children under 12 years: The dose of most medicines must be diminished in proportion of the age, to the age increased by 12. Thus at 4 years the dose will be ¼ of that of adults, viz.: 4/4+12=4/16 or ¼;at 6 years it will be 6/6+12=6/18 or ⅓. Of narcotics use even less than above, especially in infants.
Another way of calculating doses at various ages is as follows, viz.:—Taking the dose of an adult as one, or 1 drachm as base. The dose of a person from 7 to 14 years will be ½ or ½ drachm, The different proportion of doses at different ages will be: from 4 to 7 years ⅓; 4 years ¼;3 years ⅙; 2 years ⅛; 1 year 1/12 and ½ year 1/15 of one or, in other words, 1/15 of the adult dose. 14 to 21 years would be ⅔ of one.
Hypodermic Injections: As a rule hypodermic injections should be about ½ of that by mouth. By rectum about ⅘ of that by mouth.
Comparison of Doses: Approximately. A drop corresponds with a minim; a teaspoonful with a fluid drachm; a dessertspoonful with 3 fluid drachms; a tablespoonful with ½ ounce; a wineglassful to 2 ounces; a teacupful with a gill or 4 fluid ounces.
Solutions: Rules in regard to making solutions. Taking 1 grain as a base of 1% solution; we mean 1 grain of drug or 1 drop of a drug to 100 drops of water. Therefore, 1:1000 would mean 1/10 of a grain or minim to 100 drops of water, etc.