Stimulant Laxative Pregnancy: Caution — avoid in first trimester (theoretical risk of uterine stimulation); compatible in second and third trimester for short courses.

Senna

Brand names: Senokot, Manevac

Adult dose

Dose: 15–30mg (2–4 standard tablets of 7.5mg each) at night. Syrup: 10–20mL at night.

Route: Oral

Frequency: Once daily at night (acts in 8–12 hours)

Max: 30mg/day (4 tablets)

First-line stimulant laxative for constipation. Anthraquinone glycoside — acts in colon 8–12 hours after ingestion. Used alongside softener (docusate) in palliative care opioid-induced constipation. Senokot tablets 7.5mg sennosides each.

Paediatric dose

Route: Oral

Frequency: Once daily at night

Max: 15mg (2 tablets) per night

BNF for Children: 6–11 years: 7.5mg (1 tablet) at night; 12–17 years: 7.5–30mg at night. Syrup: 1 month–3 years (off-label): 2.5–5mL at night. Source: BNF for Children 2024.

Dose adjustments

Renal

No dose adjustment required.

Hepatic

No dose adjustment required.

Clinical pearls

Standard laxative in palliative care: prescribe senna routinely with all opioids (opioid-induced constipation does not develop tolerance — always add laxative).
Melanosis coli: brownish discolouration of colonic mucosa visible on colonoscopy after months of use — harmless, reverses on stopping.
Combination with docusate: senna stimulates colonic transit; docusate softens stool — complementary mechanism, widely used in palliative care.
Take at night — bowel action expected 8–12 hours later (morning). Warn patient of timing.

Contraindications

Intestinal obstruction or ileus
Severe inflammatory bowel disease
Abdominal pain of unknown cause

Side effects

Abdominal cramps (especially with higher doses)
Diarrhoea (overuse)
Melanosis coli (harmless dark discolouration of colon mucosa with long-term use)
Electrolyte disturbance (prolonged overuse — hypokalaemia)
Urine discolouration (yellow-brown — harmless anthraquinone metabolites)

Interactions

Diuretics / corticosteroids: additive hypokalaemia risk with prolonged overuse

Monitoring

Stool frequency
Electrolytes (prolonged high-dose use)

Reference: BNFc; BNF 90; NICE NG31 Palliative Care — Constipation; SPC Senokot. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Calculators

Rome IV Diagnostic Criteria for Functional Constipation · Functional GI Disorders

Drugs

Pathways