1. Condition of the stomach.
2. Condition of the patient.
(a) Idiosyncrasy. (c) Tolerance.
(b) Disease. (d) Presence of shock.
Condition of the Stomach, i. e., the rate of absorption.
It can be readily seen that a drug in solution taken into the stomach when it is empty, will be rapidly and quickly absorbed and the action immediate and positive, whereas a drug taken on a full meal, even though in solution, will have its action delayed by being absorbed slowly, and thus is more likely to undergo chemical changes which may greatly modify its action. Also, certain drugs may be so irritant as to preclude their administration on an empty stomach. Other drugs may be taken in small doses on an empty stomach, but not in large doses, because they would be ejected. Again, certain drugs may be rendered entirely worthless when taken on an empty stomach, as pancreatin.
The more soluble condition the drug is in or the more soluble it is in an acid medium, the more quickly it will be absorbed from the stomach. Also, the drug might be given in solution, well diluted, on an empty stomach, without causing irritation, when a tablet, pill, or capsule drop-pod into an empty stomach might irritate the surrounding mucous membrane sufficiently to cause pain or even ulceration. Hence, most pills, capsules, tablets, and powders, unless insoluble in the stomach, or inert or bland, or for action on the mucous membrane of the stomach, are always given after meals. The same is true of solutions, unless very well diluted, or for immediate effect, or for local stimulant action on the stomach, as a bitter tonic before meals.
By this is meant a peculiarly intense action of certain drugs on certain patients, i. e., when an intense physiologic action is caused by a dose of a drug which is known in ordinary cases to produce but slight, if any, symptoms. Patients who are found to have an idiosyncrasy against a certain drug should be told what the drug is, that they may caution their future medical attendants against giving them that drug. An occasional patient will be found who cannot take opium in any form without it causing intense cerebral excitement, unless the dose is sufficient to produce profound narcotism. Such persons are very unfortunate, as they must many times suffer pain without relief.
Some patients can take a large dose of a drug when they cannot take a small one frequently repeated. Others, after the first dose of a drug has caused intensely disagreeable symptoms, can afterward, during that particular sickness, take the drug without further discomfort. This is especially true of quinine.
This was touched upon under the discussion of the condition to be combatted, certain diseases causing the doses of certain drugs to be reduced to the minimum, and other diseases causing not only the use of, but giving the best effects from, very large, even enormous doses. This is especially true of syphilis, Where mercury or potassium iodide is used in large doses with no bad effect, and perhaps in epilepsy when large closes of bromides are given. However, in believing or reporting that in a given case an enormous dose of a poisonous drug has not only been well borne, but has seemed to have good effect and no poisonous action, we must not forget that if such a dose was given by the stomach, the stomach might not have absorbed it at all, and such reports should be taken with a good deal of scepticism. In other words, the toleration of unusually large doses of drugs known to have poisonous action is generally due to non-absorption.
By this is generally meant that a person who has become addicted to the use of a certain drug has acquired a tolerance for, or an immunity to, such a drug or drugs of that class. This is, of course, found in opium eaters and morphine habitues, or in any drug habit. It is also seen in certain diseases, as in malarial fever, where very large doses of quinine can be often tolerated without inconvenience, when the same individual in normal condition can take but moderate doses without its causing cinchonism. Also, protective inoculations can render a person immune against certain poisons. This has been proved with snake venom.
This tolerance is shown in our every-day life by tobacco-users, and by those who are accustomed to take cathartics for constipation. We also sometimes find a peculiar tolerance of narcotics, and many nervous women require enormous doses of a narcotic to quiet their pain or give them brain rest. Such knowledge of the idiosyncrasy and tolerance of a given patient to given drugs constitutes the advantage which the family physician has over a new medical attendant.
This condition of low blood pressure, dilated vessels, and almost paralysis of the whole system, is one where little or nothing will be absorbed from the stomach and intestines. Hence any drug administered by the mouth will primarily be inert and useless, or, if the patient rallies, the absorption of large doses, or frequent doses, may cause poisonous symptoms. Therefore, when there is great depression it is unjustifiable to administer strong or poisonous doses by the mouth, but resort should be had to the hypodermic syringe for the drug treatment of the case.