Before writing his prescription the physician must first decide, from the condition of the patient, as to the effect to be produced, then the agent that will best produce the desired effect, then the most desirable route under the circumstances to get the remedy into action, and then the most desirable form in which to administer it. To produce a systemic effect, drugs may be given by mouth, rectum, skin, hypodermically, intravenously, or by inhalation.

The mouth is the natural channel for the intake for all matter except oxygen. Doses, not otherwise specified, are understood to be by this route. Medicines for general effect are supposed to be administered by mouth unless there is some reason to the contrary.

It should be remembered that in some conditions, as when much undigested food is present, or when the patient is in great pain, absorption from the stomach may be delayed.

The intravenous method gives the quickest results and the dose is smallest.

Hypodermic administration is next in point of prompt action and smallness of dose. The dose is usually one-half to two-thirds of that by mouth.

Rectal administration gives slower results than by mouth, and the dose is usually 50 to 100 per cent. larger.

The local effect may be produced by any method that brings the agent into contact with the part to be affected.

By Mouth for Systemic Effect.

Solutions

It is a safe rule to make this the form of first choice and use, unless there are reasons to the contrary, as odor, taste, insolubility, etc.

Liquids Not Solutions

This includes mixtures, emulsions, etc. They are employed when an agent is administered by mouth that is insoluble in the desired vehicle and there are reasons against giving in capsules, powders, etc.; also when the taste would be objectionable if in solution. Examples are bismuth salts suspended in thick liquids, oil of turpentine in emulsion, quinine salts suspended in chocolate syrup, etc.

Capsules

This is one of the most convenient and agreeable forms for administering medicine. They are particularly useful for drugs of unpleasant taste or odor, as quinine salts, thymol, etc. The effect is not produced as quickly as when the drug is in solution, and they should not contain agents in such form as will cause irritation of the alimentary mucosa. It should be remembered that small children and many adults are unable to swallow capsules or are nauseated by them. Before prescribing capsules it is always best to ascertain if the patient can take them.

Papers

By papers is here meant doses of medicine wrapped up in papers (cht.) instead of put into capsules or other container. The form answers well for those powders that are not disagreeable in taste or odor, as calomel with milk sugar, sulphonmethane, etc.

Pills

This is a convenient form for the administration of some drugs, as silver nitrate, phosphorus, etc., and is sometimes an economic method where the drug is to be continued for a-considerable time, as in giving yellow mercurous iodide for syphilis or ferrous carbonate for chlorosis. It is not often that a prescriber should order pills to be prepared extemporaneously. Pills of silver nitrate or phosphorus cannot usually be made to advantage by the local druggist, and if it is desired to have freshly prepared doses of such agents as ferrous carbonate or yellow mercurous iodide it will be better for many reasons to order capsules. Pills are subject to many disadvantages, such as hardening and becoming insoluble, crumbling, tasting if not coated, sticking together if coated, etc.

Tablets

Hypodermic tablets and tablet triturates usually disintegrate readily when taken into the stomach, and are sometimes a convenient form for administering medicines of small dosage. If the medicine is disagreeable, as strychnine, the patient does get the benefit of it to some extent, particularly if hypodermic tablets are used. Compressed tablets are usually hard and very apt to disintegrate slowly, if at all, in the alimentary tract. Their usefulness is very limited to the prescriber, though they are sometimes a great convenience to the dispensing physician.

Cachets

This is not usually considered a practical method of administration, in this country.

By- Rectum for Systemic Effect.

Liquids

For the best results the agent should be in solution and so diluted as to be non-irritating. When possible, the rectum should be first cleansed by irrigation and the bulk of the dose should not exceed about six fluidounces for an adult.

Medicines are sometimes administered to advantage by the Murphy drip.

Suppositories

These are usually made with a vehicle of cocoa butter. They should be non-irritating and the active agents should be readily soluble.

Rectal administration is often useful, particularly when the upper alimentary tract is intolerant, as in gastric irritation or when there is much nausea, or when it is undesirable for any other reason to give a remedy by mouth, as in appendicitis, etc.