1. Due to too frequent doses.
2. Due to too long continued administration.
By cumulative effect is meant the unexpected, intense action of a drug after it has been given for some time, as differing from an immediate intense action of a drug which would show an idiosyncrasy.
1. The Too Frequent Administration of a drug which is slow of excretion will cause it to accumulate in the sys tern, and sooner or later produce a poisonous effect. Therefore, as spoken of under the heading of "the duration of the action of a drug," it is very important to remember how long it ordinarily takes a given drug to be excreted. For instance, if a drug that is excreted in eight hours was administered every two hours, at the end of eight hours five doses will have been taken, only the first of which has been completely excreted, leaving three doses acting and one beginning to act in the system.
2. Cumulative Action From Too Long Continued Administration of a Drug means the development of symptom a which show an over-action of the drug. This is of frequent occurrence and is sometimes accidental, but is often caused deliberately by pushing a drug to its full physiologic effect. In cases in which this action occurs unexpectedly and is undesired, the drug should be immediately stopped, and not again given in doses that could cause such an effect. Some drugs give notice of such an impending action by premonitory symptoms; such is true of digitalis.
In some diseases such cumulative physiologic action of certain drugs is desired. The drug is then stopped temporarily, and then again pushed to the point of tolerance, such a method of using the drug giving the best thera, The best way to combat such over-action, and which drugs will produce an over-action without danger to the patient, can be learned only by the study of the pharmacology of the drugs.