RECTAL INJECTIONS OF MEDICINES 9 



nated by the bile, and do not enter the general circulation 

 at all. 



When drugs are administered for their local action 

 on the stomach, in catarrh or ulcer, they should be given 

 half hour to an hour before feeding; if given for their action 

 in or on the intestines, they should be administered two or 

 three hours after meals. 



6. Rectal injections of medicines (enemata or clysters) are a 

 practised when the use of drugs by the mouth is inadvis- 

 able or impossible, as in unconsciousness, dysphagia, con- 

 vulsions ; also to destroy parasites (oxyurides) in the rectum, 



to influence an inflamed or ulcerated rectal mucous mem- 

 brane, and to remove intestinal contents (oil and glycerin). 



The dose of drugs by this method is generally twice 

 that by the mouth, and absorption is slower arid more im- 

 perfect. The drug should be non-irritating, soluble, and not 

 too bulky, since a small amount is necessary ( 3 i.- 3 i. dogs ; 

 5 ii.- 5 viii« horses); to avoid tenesmus and expulsion. Warm 

 starch solution (made by boiling) with a little laudanum is 

 a good vehicle for medicinal enemata, and retention of ene- 

 mata is facilated by pressure on the anus with a towel for 

 some minutes after the injection is given. 



Solids are sometimes employed by rectum in suppos- 

 itories. For general uses of enemata, see p. 30. 



7. Drugs are absorbed very slightly by the skin, and then 

 only when rubbed very vigorously into the epidermis (in- 

 unction) with lanolin, fat or oil of some kind. Mercury and 

 iodine are most commonly employed for absorption, but 

 drugs are usually applied externally for their local action 

 only and not to influence the general system through the 

 blood. 



Dosage. 

 The study of dosage is known as Posology. The action 

 of drugs is altered both in degree and kind by the dose. 

 Thus, increasing the dose would naturally lead to an in- 

 crease in the intensity of a drug's action, but it frequently 

 changes the entire character of the action as well. 



