CP-GLYCERIN

Indications

• Constipation
• Preparation for surgical or diagnostic procedures involving the rectum
• Decreasing intraocular pressure in certain ocular conditions

Dosage

Children: For children aged 2 to 6 years, 2 g to 5 g of glycerin may be used as a suppository. Children aged 6 to 12 years may use 5 g to 10 g as needed. For specific pediatric dosing, please refer to the BNF for Children.

Adults: For rectal use, 4 g to 10 g of glycerin may be administered as a suppository as needed.

Mechanism of action

When administered rectally, glycerin draws water from the tissues into the feces due to its hygroscopic action, which reflexively stimulates bowel evacuation. Additionally, glycerin creates an osmotic gradient that leads to a decrease in intraocular pressure by facilitating fluid movement from the aqueous and vitreous humors into the bloodstream.

Pharmacodynamics

Glycerin is classified as an osmotic laxative, which acts to retain water in the fecal matter, softening stools and making them easier to pass. Its local irritant effects also contribute to its laxative properties. Glycerin suppositories typically produce a bowel movement within 15 to 30 minutes of administration.

Pharmacokinetics

Glycerin is readily absorbed from the gastrointestinal tract when taken orally and is metabolized primarily in the liver. It is distributed widely throughout the body, with excretion occurring primarily via the kidneys. The onset of action for glycerin when used as a laxative is relatively quick, particularly when used rectally.

Contra-indications

• Severe dehydration
• Severe renal impairment
• Intestinal obstruction
• Appendicitis

Adverse effects

• Abdominal cramps
• Diarrhea
• Nausea
• Vomiting
• Electrolyte imbalance

Interactions

• May enhance the effects of other laxatives
• Caution with concurrent use of diuretics due to potential electrolyte imbalance

Precautions

• Use with caution in patients with renal impairment
• Monitor electrolytes in patients with prolonged use
• Not recommended for long-term use

Pregnancy

Glycerin is generally considered safe during pregnancy but should be used under medical advice.

Breast-feeding

Glycerin is excreted in breast milk in small amounts and is considered safe for use while breastfeeding.

Storage

Store at room temperature, away from moisture and heat.

Formulations

• Glycerin suppositories
• Glycerin oral solution

Mechanism of action

When administered rectally, glycerin exerts a hygroscopic and/or local irritant action, drawing water from the tissues into the feces and reflexively stimulating evacuation. Glycerin decreases intraocular pressure by creating an osmotic gradient between the blood and intraocular fluid, causing fluid to move out of the aqueous and vitreous humors into the bloodstream. Glycerin (glycerol) and sorbitol are hyperosmotic laxatives. When administered rectally, glycerin and sorbitol exert a hygroscopic and/or local irritant action, drawing water from the tissues into the feces and reflexly stimulating evacuation. The extent to which the simple physical distention of the rectum and the hygroscopic and/or local irritant actions are responsible for the laxative effects of some of these drugs is not known. Only extremely high oral doses of sorbitol (25 g daily) or glycerin exert laxative action. /Glycerin/ decreases intraocular pressure by creating an osmotic gradient between the blood and intraocular fluid, causing fluid to move out of the aqueous and vitreous humors into the bloodstream. The physicochemical effects of a series of alkanols, alkanediols and glycerol on erythrocyte shape and hemolysis at 4 and 20 degrees C were examined. We calculated the dielectric constant of the incubation medium, Ds, and the dielectric constant of the erythrocyte membrane Dm in the presence of organic solutes. The ratio Ds/Dm = -38.48 at 20 degrees C defines the normal biconcave shape in a medium without hemolytic agents. A decrease in Ds/Dm favors externalization or internalization with consequent hemolysis. Alkanols and alkanediols convert biconcave erythrocytes into echinocytes, which is accompanied by an increase in the projected surface area. Glycerol converts biconcave erythrocytes into stomatocytes, which was accompanied by a marginal decrease in the projected surface area. Progressive externalization in alkanols and alkanediols or internalization in glycerol resulted in a decrease in the projected surface area and the formation of smooth spheres. The degree of shape change induced was related to the degree of hemolysis and the ratio Ds/Dm. A decrease in temperature reduced both the degree of shape change and hemolysis. .../Thus/ physicochemical toxicity may be a result of a temperature dependent hydrophobic interaction between the organic solutes and the membrane and is best interpreted by the ability of the solutes to change Ds and Dm.

Pharmacodynamics

Glycerin is commonly classified as an osmotic laxative but may act additionally or alternatively through its local irritant effects; it may also have lubricating and fecal softening actions. Glycerin suppositories usually work within 15 to 30 minutes.