Glycerol Suppository

Glycerol (glycerin) suppository is a hyperosmotic rectal laxative that triggers rectal emptying within minutes. It is used for occasional constipation, softening hard rectal stool, bowel training and in infants.

Classification. Hyperosmotic rectal laxative; lubricant.

Mechanism. Glycerol draws water into the rectum by osmosis, softening stool, and irritates the rectal mucosa, stimulating the defaecation reflex. It also lubricates the passage of hard stool.

Pharmacodynamics. Evacuation occurs within 15 to 30 minutes of insertion.

Pharmacokinetics. Minimal absorption from the rectum. Any absorbed glycerol is metabolised in the liver.

Rectal doses. One suppository when needed, usually after breakfast.

Constipation and hard rectal stool.

• Age 12 years and over and adults: 4 g.

• Age 1 to 11 years: 2 g.

• Infants under 1 year: 1 g.

• Use once daily as needed; do not use regularly for more than 1 week without review.

Bowel training and neurogenic bowel (for example spinal cord injury). One suppository at the same time each day, often combined with digital stimulation, under specialist direction.

Faecal loading from opioids. Use when rectal stool is hard, combined with oral laxatives.

Kidney and liver adjustment. None.

Contraindications. Intestinal obstruction; acute abdomen or undiagnosed abdominal pain; undiagnosed rectal bleeding; acute proctitis; painful anal fissure or abscess; hypersensitivity.

Common adverse effects. Rectal irritation or burning, urge to defaecate and mild cramp.

Serious adverse effects.

• Rectal mucosal injury with repeated use or forceful insertion.

• Rectal bleeding (rare).

• Dependence on rectal stimulation with long-term regular use.

Major interactions. No significant drug interactions. Other laxatives have additive effects.

Special groups.

• Pregnancy: acceptable.

• Breastfeeding: compatible.

• Children: dose by age; first-line rectal treatment for infants.

• Older adults: acceptable; check for faecal impaction.

• Diabetes: not absorbed in meaningful amounts.

• Kidney impairment: no adjustment.

• Liver impairment: no adjustment.

Formulations. Suppositories 1 g, 2 g and 4 g.

Administration.

• Moisten the suppository with water.

• Insert pointed end first, past the anal sphincter.

• Retain for 15 to 30 minutes if possible, or until a strong urge.

• Wash hands before and after.

Baseline. Rectal examination for impacted stool where indicated, and exclusion of obstruction.

Monitoring.

• Evacuation response within 30 minutes.

• Perianal skin and mucosal irritation.

• Frequency of need.

Therapeutic drug monitoring. Not applicable.

Stopping. No taper is needed. Stop for irritation, bleeding or when regular bowel habit returns.

Referral and escalation. Seek review if there is no result after 2 doses, if constipation persists over 1 week, or if there is rectal bleeding or severe pain. Manual evacuation or enema may be needed for faecal impaction.