7. The Nature Of The Disease

In great pain, as in peritonitis, morphine may be borne in doses that would ordinarily be poisonous. On the other hand, in cyanosis or conditions with bad breathing, morphine should be used with caution because of its tendency to depress the respiration. In malaria, quinine can be borne in larger doses than when it is used for other purposes.

Again, in Bright's disease or other conditions involving the eliminating organs drugs may more readily accumulate in the system and cause cumulative poisoning; and in functional or organic disturbance of the liver certain substances, like phenol or morphine, may have a more pronounced poisonous effect than otherwise.

8. The Object Of The Medication

Quinine as a bitter appetizer may be given in doses of one or two grains, while quinine for malaria is given in a single large dose of 15 or 20 grains, followed by 5 grains three times a day for a month. In a cough mixture for a child syrup of ipecac is given in dose of 2 to 5 minims, but in croup, where an emetic effect is desired, a whole teaspoonful is administered.

It is to be noted that preparations for local action are active according to their percentage strength rather than according to the actual amount of drug employed.

9. The Form Of The Remedy

As a rule, this makes but little difference; yet, other things being equal, liquids are more rapidly active than solids, and alcoholic liquids more than aqueous. Active principles are more rapid than crude drugs, powders and dry-filled capsules than pills, fresh-made pills than coated pills. Some cathartic drugs, like aloes and cascara, are more effective cathartics than their active principles. This is because of the extractive matter present, which retards absorption and keeps the active principles in the alimentary tract until they reach the colon.

10. The Channel of Administration. - It has usually been taught that the hypodermatic dose should be half, and the dose by rectum twice, that by mouth. In a number of instances, however, it has been demonstrated that drugs are as quickly absorbed from the rectum as from the stomach, or even more quickly; and also that, in ordinary circumstances, most drugs are absorbed from the stomach or duodenum with sufficient rapidity to give the full effect of the drug in a short time. Therefore, since rectal and hypodermatic medication are resorted to only under special circumstances, their dose is the same as that by mouth. In rectal medication the strength of the preparation rather than the total dose is usually desired, for the rectum is seldom resorted to for any but local medication. In intravenous medication the dose is a special one for the few drugs that may be so administered, and is usually comparatively small. In conditions of edema, hypodermatic medicaments may be retarded in their absorption, and in congestive conditions of the stomach and bowels, mouth doses may be retarded.

11. The Time of Administration. - After meals the dose is diluted and absorption delayed by the admixture with the stomach contents; so if a rapid effect is desired, a larger dose must be given. On the contrary, the empty stomach allows immediate local action and more ready absorption, as commonly observed in the greater activity of alcoholic drinks taken before meals.

12. The Frequency of Administration. - It goes without saying that the dose of a powerful drug is less if it is administered every hour or two than if given three times a day.

By administration is meant the manner in which the remedy is to be used. Remedies are administered to obtain either a direct local action, a systemic action, or a remote local action.

The direct local action is the action at the place at which the drug is applied, as on the skin, or in nose, throat, stomach, urethra, etc. To obtain direct local action, ointments, liniments, plasters, etc., are employed. Local remedies may or may not require to be absorbed. Talcum powder applied to a chafed skin, or bismuth subnitrate given for irritated stomach or bowels, acts by coating the skin or mucous membrane and is not absorbed; while cocaine, to produce a local anesthetic effect, must be absorbed to get at the nerve-endings or nerves beneath the epidermis.

The systemic action is the action of the drug after its absorption into the circulation, as that of strychnine on the spinal cord, or pilocarpine on the nerve-endings in the sweat-glands.

The remote local action is the effect of the drug as it is being excreted, e. g., the irritation of the bowels by mercuric chloride as it is passed out by the colon glands, or the antiseptic action of urotropine as it is eliminated in the urine. To obtain either a systemic action or a remote local action the drug must be absorbed; that is, must become a constituent of the body fluids.