This section is from the book "Materia Medica: Pharmacology: Therapeutics Prescription Writing For Students and Practitioners", by Walter A. Bastedo. Also available from Amazon: Materia Medica: Pharmacology: Therapeutics: Prescription Writing for Students and Practitioners.
In prescription writing, clearness is the important thing and Latin is the medium of expression, but certain forms have become approved, and certain modes of expression are accepted as the best custom. The following precepts are according to "good usage":
1. Each ingredient name shall have a separate line.
2. Each line begins with a capital letter.
3. Ditto marks are not permissible.
4. The names of the most active ingredients are placed first, the names of flavors and correctives afterward, the name of the diluent last. In a liquid prescription the names of solids, if active medicinally, before those of liquids, and the vehicle last.
5. In a title the name of the class of preparation (as pilula, tinctura, elixir, etc.) comes first; a modifying adjective usually last, as syrupi sarsaparillae compositi. Of salts, the name of the base first, as sodii bromidi; of acids, the term for acid first, as acidi hydrochlorici.
6. Latin is regularly employed for the names of the ingredients and for the directions for compounding.
7. In the directions for the label, Latin is employed only in certain recognized expressions, hence Latin and English are mixed indiscriminately. The pharmacist writes these directions on the label in English.
8. When in doubt as to the correct Latin expression, write in English; when uncertain of the correct Latin ending, omit it. The understanding of the physician's order by the pharmacist is of more importance than the correctness of the Latin. Complicated Latin constructions add the risk of being wrongly interpreted by the pharmacist, who is not of necessity a Latin scholar.
9. For amounts over two ounces make the total of a liquid prescription conform with the sizes of bottle found in the phar-macies; for if a bottle is only partly filled, the patient may think that some of the medicine has been spilled or an error made by the pharmacist. The vials used in the United States are: 1,2, and 4 dram, 1, 2, 3, 4, 6, 8, 12, 16, and 32 ounce.
10. In acute illness order a small number of doses, both to permit frequent change in the treatment and to avoid having the medicine outlast the sickness. The larger amounts may be prescribed if the dose is to be repeated frequently, or if the medicine is to be continued definitely without change for a long time.
11. When writing for more than the ordinary dose of a potent drug, as for one grain of morphine sulphate or 1/10 grain of strychnine sulphate, always double underline the quantity or write O. K. or dose correct, otherwise the pharmacist may think it an error and refuse to dispense the prescription till the doctor is communicated with. Do not employ exclamation marks for this purpose, for these have been mistaken for Roman numerals. Professor Remington reports a prescription for one grain of morphine sulphate to be divided into two powders. The physician intended to write Morphinae sulphatis, gr. j !! - the exclamation marks indicating that he intended the large dose. But he did actually write Morphinae sulphatis, gr. iii, the exclamation marks being turned upside down.
12. When the formula or name of the medicine is desired on the label the term "Label," " on label," "Formula on label," may replace or be added to other directions for the label. Examples are: "Sig. - Label," or "Sig. - Take three times a day - Formula on label."
13. The terms "For external use" and "Shake before using" need not be specified in the directions, for, when the nature of the preparation indicates it, these are regularly placed upon the bottle by the pharmacist. But, unless the physician so directs, the term "Poison!" is never placed upon a prescription for internal use, as for strychnine tablets or Fowler's solution. And it is often omitted from poisonous preparations for external use, as belladonna liniment.
14. The letters P. P. following a patient's name stand for "poor patient," and secure from the pharmacist his lowest price. The expressions "ne repetatur," or "not to be repeated," and "give no copy," are regularly heeded by the pharmacist.
15. The use of the term "as directed" or "use as directed" as the sole direction for the patient should be avoided if possible, for it does not indicate to the druggist how or in what dose the remedy is to be employed. The physician thus lacks the pharmacist's valuable check upon the prescription. If for esthetic or other reasons it is desired to omit the directions, as for douches, injections, etc., they should be given to the patient in writing; for patients, especially those who are nervous or quite ill, are prone to forget verbal directions, or, what is worse, to remember (!) them wrongly.
16. Where there can be no possible misinterpretation, abbreviation may be good usage. See below.
17. Never sign a prescription or let it get out of your hands without first reviewing it. Because of distraction of the physician's attention by anxious or talkative friends, or for other reasons, errors in prescriptions are of frequent occurrence. The most common error is omission or transposition of the amounts of the ingredients. For example, one recently seen by the writer called for potassium iodide, gr. j, and mercuric iodide, 3iij, the amounts being transposed.
If a pharmacist 'phones you or calls upon you relative to the interpretation of one of your prescriptions, do not take offense as if it were an insult for any one to suppose your handiwork anything less than perfect. On the contrary, be grateful to the pharmacist; for he will protect you and will not tell the patient of your error, even though he has to shoulder the blame himself for the delay in the dispensing of the prescription. The pharmacist is no more prone than other people to make trouble for himself unnecessarily, and if he questions one of your prescriptions, you may take it for granted that he has a reason for his action, even though it may not be apparent to you.