3. Form Of The Drug

Form Of The Drug. This controls largely the rate of absorption, hence, the dosage. Before any substance enters circulation it must be in solution, and the nearer medicines approach the liquid form the quicker will they have effect and the smaller will be the doses required, consequently, it takes less in tincture than in powder or pill form.

4. Condition Of The Drug

Condition Of The Drug. The same species do not always produce drugs of uniform strength; thus cinchona, opium, nux vomica, rhubarb, senna, etc., are by no means regular, as the total alkaloids of cinchona may range from 2-10 p. c; opium, 4-24 p. c, etc.; therefore, to have like results varying quantities must be given. This strength-difference is due largely to soil, climate, cultivation, season of year when collected, curing, duration on the market, possible adulterations, etc.

5. Conditions Of The Individual

Conditions Of The Individual. These are not always the same; sex, race, temperament, idiosyncrasy, congenital tolerance, acquired tolerance (mithridatism), climate, occupation, imagination, mental emotion, disease, and habitual use all affect the dosage required in individual cases. Thus, females demand less than males; strong, burly races more than weaker ones; sanguine temperaments cannot tolerate stimulants; nervous temperaments must use purgatives cautiously; bilious temperaments need mercurials, while these are injurious to lymphatic temperaments. Idiosyncrasies vary in people - some vomit at the odor of ipecac or purge by smelling croton oil; others are affected little or greatly by opium, mercury, arsenic, belladonna, cocaine, iodides, etc. Warm climates demand smaller doses of purgatives and larger doses of antiperiodics. Occupation largely controls doses, as those exposed and under hard labor require unlike quantities to those in light pursuits, sedentary habits, indoor surroundings, etc. Imagination has its effect, as in a degree one's frame of mind can will or not will results. Mental emotion, either with or without disease, as a rule, demands larger doses than when free from any undue excitement. Habitual use lessens medicinal power, the dose having to be increased gradually, as with cathartics, opium, arsenic, etc. Disease modifies dose, as in tetanus, peritonitis, cancer, cholera, etc., excessive quantities of morphine are required and well tolerated; in typhoid fever abnormal amount of stimulants may be used, as alcohol, brandy, etc.; in pneumonia excessive doses of tartar emetic may be given without nausea, while during menstruation, lactation, pregnancy, etc., smaller doses should be administered.

6. Incidental Conditions

Incidental Conditions. Besides the preceding, we have some other factors influencing the variability of doses: State of the stomach,empty, full, active, sluggish, etc. - under certain disorders it will not assimilate medicines at all, when administration must be by other channels. Cumulative action of some drugs requires cautious doses; this may arise from slower elimination than absorption - mercury, lead; or the elimination may suddenly be arrested by the drug causing contraction of renal vessels, when the system has become saturated - digitalis, strychnine; or again, the intestinal contents may quickly be changed, so that from a slow we get rapid absorption; rate of excretion modifies doses - when rapid, small and oft-repeated quantities are more advantageous than larger ones, and as an outgrowth of this we have now the praiseworthy tendency of diminished dosage, as with calomel, etc.; pathological conditions modify the effects of drugs very considerably; thus antipyretics in fever reduce temperature, but have no effect on it in health; bromides lessen convulsions in epilepsy, but depress very slightly the normal brain, etc.