CHAPTER III. 

 POSOLOGY. 



The British Pharmacopoeia makes the following statement in regard 

 to the doses as given in it. "The doses mentioned in the pharmacopoeia 

 are intended to represent the average range in ordinary cases, for adults. 

 They are meant for general guidance, but are not authoratively enjoined 

 by the council. The medical practitioner must act upon his own respon- 

 sibility as to the doses of any therapeutic agents he may administer." 

 This statement is a very important one and one that should be thoroughly 

 understood by every medical practitioner. Firstly, the official doses repre- 

 sent the average range in ordinary cases. The deviations from the ordinary 

 that are most likely to be met with must be considered. Weight. Roughly 

 the larger and more robust the individual the larger the dose of most 

 drugs that my be given to him. Small and weakly individuals should al- 

 ways receive small doses of any remedy at first. Sex. Women are often said 

 to be less resistant to the action of drugs than men are but as a rule little 

 distinction is made between the sexes. It must however be born in mind 

 that at the time of pregnancy or menstruation any drugs that bring about 

 changes in the blood-supply to the uterus or that would set up movements 

 in its musculature should be either entirely avoided or given in very small 

 doses and with caution. Also it must be remembered that many drugs are 

 excreted in the milk and may readily make the milk unpalatable or even 

 dangerous to a suckling child. Amongst the drugs excreted by the mam- 

 mary glands are the oils of anise and dill, turpentine, copaiba, the purgative 

 principles of rhubarb, senna, and castor oil, opium, iodine, also some of 

 the metals antimony, arsenic, iron, lead, mercury and zinc. Idiosyncrasy. 

 Every person differs from all others more or less. Each person is not 

 only physically but also chemically a distinct individual. These personal 

 differences are usually quantitively so small as to occasion little or no 

 difficulty but occasional individuals are met with who deviate very widely 

 from the normal in respect to some one or more drugs. Such individuals 

 as are abnormally affected by any drug are said to have an idiosyncrasy 

 for the drug. Drugs in regard to which idiosyncrasy is likely to be en- 

 countered are morphine, and its allies, mercury, bromides, copaiba, arsenic, 

 iodides, quinine, etc. Idiosyncrasy is often an inherited characteristic. 

 Tolerance. The continued use of a drug is very apt to make any individual 

 less susceptible to its pharmacological action and to necessitate the ad- 

 ministration of larger doses, this is known as tolerance. Tolerance often 

 occurs with alcohol, morphine, arsenic, vegetable purgatives, cocaine. 



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