DOSAGE.
The following general rules will aid the student in remembering the safe dose of many important preparations:
1. Tinctures of very active drugs, such as opium, digitalis, belladonna, physostigma, nux vomica, gelsemium, arnica, and capsicum may be given in doses of from 5 to 20 minims (0.3-1.2 c.c.), except the tinctures of aconite, veratrum viride, iodin, and cantharides, the dose of which is from 1 to 5 minims (0.06-0.3 c.c.).
2. Tincture of less active drugs, such as gentian, calumba, krameria, quassia, valerian, cinchona, kino, may be given in doses of from ½ to 1 dram (2-4 c.c.).
3. Solid extracts of active drugs may be given in doses of from ⅙ to ¼ of a grain (0.01-0.016 gm.).
4. Solid extracts of less active drugs may be given in doses of from ½ to 5 grains (0.03-0.3 gm.) or more.
5. Dilute acids (hydrochloric, nitric, nitrohydrochloric, sulphuric) may be given in doses of from 5 to 20 minims (0.3-1.3 c.c.), except dilute hydrocyanic acid, the dose of which is from 1 to 5 minims (0.06-0.3 c.c.).
6. All medicated syrups, except the syrup of iodid of iron and the compound syrup of squill, may be given in doses of 1 to 2 drams (4-8 c.c.) or more.
7. All infusions may be given in doses of ½ to 1 ounce (15-30 c.c.) or more, except the infusion of digitalis, the dose of which is from 1 to 4 drams (4-15 c.c.).
8. All official mixtures may be given in doses of from 1 to 4 drams (4-15 c.c.).
9. All spirits may be given in doses up to 1 dram (4 c.c.), except the spirit of nitroglycerin (glonoin), the dose of which is from 1 to 5 minims (0.06-0.3 c.c.), the spirit of phosphorus, the dose of which is from 5 to 15 minims (0.3-1 c.c.), and the spirit of bitter almond, the dose of which is from 5 to 10 minims (0.3-0.6 c.c.).
10. All waters (aquæ) may be given in doses up to 1 ounce (30 c.c.), except aqua ammoniæ, aqua chlori, and aqua laurocerasi (cherry-laurel), the dose of which is about ½ dram (2 c.c.).
11. Volatile or essential oils may be given in doses up to 5 minims (0.3 c.c.) or more, except the oil of bitter almond, the dose of which is from ¼ to ½ minim (0.015-0.03 c.c.).
TO ASCERTAIN DOSES OF MEDICINE
FOR CHILDREN.
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 | 152 |
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.
THE DOSE OF DRUGS ADMINISTERED
SUBCUTANEOUSLY AND BY THE RECTUM.
The dose of a drug given hypodermically is usually about one-half the quantity given by the mouth, while twice as large a dose is generally given by the rectum as would be given by the mouth.
PROPER TIME TO TAKE MEDICINES.
Alkalis should be given before food. Iodin and iodids should be given on an empty stomach, when they rapidly diffuse into the blood. If given during digestion the acids and starch alter and weaken the digestion. Acids, as a rule, should be given between the digestive acts, because the mucous membrane of the stomach is in a favorable condition for the diffusion of the acids into the blood. Acids may be given before food when prescribed to check the excessive formation of the acids of the gastric juice. By giving it before meals you check the osmosis stomachward of the acid-forming materials. Irritating and dangerous drugs should be given directly after food, such as the salts of arsenic, copper, zinc, and iron, except where local conditions require their administration in small doses before food. Oxid and nitrate of silver should be given after process of digestion is ended; if given during food, chemic reactions destroy or impair their special attributes and defeat the object for which they were prescribed. Metallic salts, especially corrosive sublimate, also tannin and pure alcohol, impair the digestive power of the active principle of the gastric juice, so should appear in the stomach during its period of inactivity. Malt extracts, cod-liver oil, phosphates, etc., should be given with or directly after food, so that they may enter the blood with the products of digestion.