Usage
- Glycerol is prescribed for the treatment of occasional constipation, reduction of intraocular pressure (IOP) before eye surgery or in acute glaucoma attacks, and as an adjunct in hyperhydration strategies for athletes. It can also be used to reduce cerebral edema.
- Pharmacological classification: Osmotic laxative, osmotic diuretic, humectant.
- Mechanism of action: Glycerol exerts its laxative effect by drawing water into the rectum, softening the stool and promoting bowel movements. Its diuretic effect stems from its ability to increase the osmolarity of the blood, leading to fluid shifts and increased urination. The humectant properties of glycerol help retain moisture in skin and mucous membranes, offering topical benefits for dry or irritated skin conditions.
Alternate Names
- Glycerin, glycerine, propane-1,2,3-triol.
- Brand names: Fleet Glycerin Suppositories, Pedia-Lax, Osmoglyn (oral), and various generic preparations.
How It Works
- Pharmacodynamics: Orally administered glycerol is absorbed from the gastrointestinal tract and distributed throughout the body. It increases blood plasma osmolarity, leading to a shift of fluid from intracellular and interstitial spaces into the vascular compartment. This effect leads to diuresis and reduced IOP and intracranial pressure. Rectally, glycerol acts as a hyperosmotic laxative, drawing water into the rectum and stimulating peristalsis.
- Pharmacokinetics: Glycerol is readily absorbed following oral administration. It is metabolized primarily in the liver, and a small amount is excreted unchanged by the kidneys.
- Mode of action: Glycerol’s osmotic properties underlie its various effects. It increases the osmotic gradient across cell membranes, drawing water into the compartment where glycerol is present.
- Elimination pathways: Primarily hepatic metabolism, with a small amount excreted unchanged in the urine.
Dosage
Standard Dosage
Adults:
- Constipation (rectal): 2-3 g as a suppository or 5-15 mL as an enema, once.
- Elevated IOP/Intracranial pressure (oral): 1-2 g/kg body weight as a single dose. Maintenance doses of 500 mg/kg every 6 hours can be used.
Children:
- Constipation (rectal): 2-6 years: 1-1.7 g suppository or 2-5 mL enema. Over 6 years: 2-3 g suppository or 5-15 mL enema.
- Elevated IOP/Intracranial pressure (oral): 1-1.5 g/kg as a single dose. May repeat every 4-8 hours if needed.
Special Cases:
- Elderly Patients: Start with the lower end of the dose range and monitor closely for dehydration.
- Patients with Renal Impairment: Caution is advised, as glycerol can exacerbate dehydration. Dosage adjustment may be required.
- Patients with Hepatic Dysfunction: Use with caution and monitor closely. Dosage adjustment may be required.
- Patients with Comorbid Conditions: Patients with diabetes may experience hyperglycemia after glycerol administration. Cardiovascular patients should be monitored for fluid overload.
Clinical Use Cases
- Intubation: May be used to reduce intracranial pressure prior to or during intubation.
- Surgical Procedures: Glycerol can reduce IOP prior to ophthalmic surgeries.
- Mechanical Ventilation: Use with caution in mechanically ventilated patients due to the risk of fluid overload.
- Intensive Care Unit (ICU) Use: May be used to reduce intracranial pressure in ICU settings, but close monitoring is crucial.
- Emergency Situations: Glycerol may be used in the management of acute glaucoma and cerebral edema.
Dosage Adjustments:
- Renal or hepatic dysfunction warrants careful consideration of fluid balance and potential need for dose adjustments.
Side Effects
Common Side Effects:
- Headache, dizziness, nausea, vomiting, diarrhea, bloating, thirst.
Rare but Serious Side Effects:
- Cardiac arrhythmias, circulatory overload, heart failure, severe pulmonary edema.
Long-Term Effects:
- With chronic rectal use, dependence can develop.
Adverse Drug Reactions (ADR):
- Hypersensitivity reactions (rare).
Contraindications
- Hypersensitivity to glycerol.
- Intestinal obstruction, severe impaction.
- Anuria, severe dehydration, acute pulmonary edema, severe cardiac decompensation.
- Severe renal or hepatic impairment.
Drug Interactions
- May interact with acetaminophen, increasing the risk of hepatotoxicity.
- Concomitant use with other diuretics may lead to excessive dehydration.
- May interfere with the absorption of certain medications administered orally.
Pregnancy and Breastfeeding
- Pregnancy Safety Category: C (FDA).
- Limited human data available. Use only if benefits outweigh risks.
- Breastfeeding: Small amounts of glycerol may be excreted in breast milk. Generally considered safe for use during breastfeeding.
Drug Profile Summary
- Mechanism of Action: Osmotic agent.
- Side Effects: Headache, dizziness, nausea, vomiting, diarrhea.
- Contraindications: Intestinal obstruction, anuria, severe dehydration.
- Drug Interactions: Acetaminophen, diuretics.
- Pregnancy & Breastfeeding: Use with caution during pregnancy; safe for breastfeeding.
- Dosage: Varies depending on indication and route of administration.
- Monitoring Parameters: Fluid balance, electrolyte levels, IOP/intracranial pressure, bowel function.
Popular Combinations
Precautions
- General Precautions: Evaluate renal and hepatic function before use. Monitor for signs of dehydration, especially in elderly patients.
- Specific Populations: Caution in pregnancy (especially first trimester). Monitor infants of breastfeeding mothers for potential diarrhea.
- Lifestyle Considerations: Maintain adequate fluid intake.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Glycerol?
A: The dosage varies depending on the indication and route of administration. For constipation, 2-3 g rectally as a suppository or 5-15 mL as an enema. For elevated IOP or intracranial pressure, 1-2 g/kg orally.
Q2: How does glycerol work as a laxative?
A: It acts by drawing water into the rectum through osmosis, softening stool and promoting a bowel movement.
Q3: Can glycerol be used during pregnancy?
A: Glycerol is FDA Pregnancy Category C. Use with caution, weighing the benefits against potential risks. It is generally considered safe for use during breastfeeding.
Q4: What are the common side effects of glycerol?
A: Headache, dizziness, nausea, vomiting, diarrhea, thirst, and bloating.
Q5: How quickly does glycerol work for constipation?
A: Rectal glycerol typically produces a bowel movement within 15-60 minutes.
Q6: Are there any drug interactions with glycerol?
A: Yes, glycerol may interact with certain medications, including acetaminophen and other diuretics.
Q7: Can glycerol be used in children?
A: Yes, glycerol can be used in children, with appropriate dosage adjustments based on age or weight. Suppositories are typically used for children older than 2 years.
Q8: Can glycerol be used for conditions other than constipation?
A: Yes, glycerol can be used to reduce IOP before eye surgery or in acute glaucoma, to treat cerebral edema, and as part of hyperhydration strategies for athletes.
Q9: What are the contraindications for glycerol use?
A: Glycerol is contraindicated in cases of hypersensitivity to glycerol, intestinal obstruction, anuria, severe dehydration, acute pulmonary edema, and severe cardiac decompensation.
