Maximum Dose of Senna for Adults
According to the FDA drug label, the maximum dose of senna for adults is 3 teaspoons (15 mL) twice daily. 1
Dosing Guidelines
The recommended dosing for senna in adults follows this pattern:
- Initial dose: 2-3 teaspoons (10-15 mL) once daily, typically taken at bedtime 1
- Maximum dose: 3 teaspoons (15 mL) twice daily 1
- Tablet formulation: The American Gastroenterological Association (AGA) guideline indicates that when using tablets, the recommended maximum is 4 tablets twice per day 2
Mechanism and Clinical Considerations
Senna is a stimulant laxative that works by:
- Increasing intestinal motility
- Promoting fluid secretion into the intestinal lumen
- Typically producing effects within 6-12 hours of administration
Important Clinical Considerations
- Titration approach: Dose should be adjusted based on symptom response and side effects 2
- Cost-effective option: Senna is relatively inexpensive (<$50 monthly) compared to prescription constipation medications 2
- Duration of use: While the AGA guideline notes that long-term safety and efficacy are unknown, senna is generally recommended for short-term use or as rescue therapy 2
Potential Adverse Effects
When using senna at maximum doses, be aware of these potential adverse effects:
- Common side effects: Abdominal cramping, diarrhea (especially during initial weeks of treatment) 2, 3
- Rare but serious: Perineal blistering has been reported, particularly with higher doses and prolonged skin contact with stool 3
- Electrolyte imbalances: Prolonged or excessive use can cause diarrhea and electrolyte disturbances 2
Clinical Pearls
- Senna is available in various formulations including liquid, tablets, and teas (where dosing may be difficult to calculate) 2
- For patients requiring higher doses, advise frequent toileting or diaper changes to minimize skin exposure to stool 3
- Consider alternative laxatives like polyethylene glycol (PEG) if patients experience significant cramping or discomfort with senna 2
Despite common concerns about tolerance development with long-term use, research has not demonstrated conclusive evidence of this phenomenon 3.