senna / sennosides
Brand: Senokot, Ex-Lax
Prototype: bisacodyl
Drug Class: stimulant laxative
Drug Family: GI agent
Subclass: anthraquinone stimulant laxative
Organ Systems: gastrointestinal
Mechanism of Action
Sennosides are hydrolyzed by colonic bacteria to active anthraquinone metabolites (rhein anthrone), which stimulate the myenteric plexus, increase colonic motility, and promote water and electrolyte secretion into the colon.
colonic myenteric plexus (via anthraquinone metabolites)
Indications
- constipation (short-term)
- opioid-induced constipation (combined with docusate)
- bowel preparation
Contraindications
- intestinal obstruction
- acute abdomen
- inflammatory conditions of the GI tract
Adverse Effects
Common
- abdominal cramping
- diarrhea
- nausea
Serious
- electrolyte imbalances (chronic use)
- melanosis coli
- laxative dependence
Pharmacokinetics (ADME)
| Absorption | sennosides are not absorbed in the small intestine; converted to active metabolites in the colon |
| Distribution | minimal systemic distribution |
| Metabolism | colonic bacteria hydrolyze to active anthraquinones |
| Excretion | fecal |
| Half-life | not applicable (minimal absorption) |
| Onset | 6–12 hours |
| Peak | varies |
| Duration | varies |
| Protein Binding | minimal |
| Vd | minimal |
Drug Interactions
| Drug / Agent | Mechanism | Severity |
|---|---|---|
| diuretics | additive electrolyte loss with chronic use | moderate |
Nursing Considerations
- Most commonly used as part of a senna-docusate combination for opioid-induced constipation in palliative care and chronic opioid users.
- Advise patients to take at bedtime with a full glass of water; bowel movement typically occurs in 6–12 hours.
- Not intended for chronic daily use; laxative dependence and hypokalemia can occur.
- Warn patients that pink-red or brown urine discoloration may occur (harmless anthraquinone metabolite excretion).
Clinical Pearls
- Senna plus docusate (Senokot-S) is the first-line regimen for opioid-induced constipation; the combination addresses both decreased motility (senna) and dry stool consistency (docusate).
- Routine prophylactic use in patients started on opioids is the standard of care in palliative medicine.
Safety Profile
Pregnancy generally-safe
Lactation use-with-caution
Renal Adjustment Not required
Hepatic Adjustment Not required
TDM Not required
Concordance Terms
Cross-referenced clinical concepts — click any term to see all content where it appears.