Glycerin may be used as in enema for the relief of constipation. It acts as a local irritant, stimulating contractions of the colon, as well as lubricating and drawing water into the stool. It is sometimes mixed in a solution with water and administered in an enema bag or bucket, or can be used alone. If given alone, a glass or metal rectal syringe is frequently used in Place of an enema bag or bucket. This is due to the fact the thickness of glycerin may prevent it flowing easily through a tube. The usual procedure is to have the patient lie on their left side, or, if the patient is in good health, the knee-chest position may be used. The nozzle on the syringe is inserted into the rectum and the glycerin solutin is administered slowly by pressing on the plunger. A rubber bulb syringe may also be used. After receiving the enema, the patient maintains the position for at least 15 minutes if possible. A single enema should be enough to relieve most cases of constipation, but if a followup enema is necessary, a soapsuds or tap water enema should be used.