Normal Nighttime Laxative Syrup Dosing
For senna syrup taken at bedtime, adults should start with 2-3 teaspoons (10-15 mL) once daily, with a maximum dose of 3 teaspoons (15 mL) twice daily, though starting at the lower end minimizes side effects. 1
Senna Syrup Dosing Guidelines
Standard Adult Dosing
- The FDA-approved dosing for senna syrup is 2-3 teaspoons (10-15 mL) once daily at bedtime for adults and children 12 years and older 1
- The maximum allowable dose is 3 teaspoons (15 mL) twice daily 1
- Starting at the lower end of the dosing range (2 teaspoons/10 mL) is advisable to minimize abdominal cramping and diarrhea 2
Timing and Administration
- Senna should be taken at bedtime as directed, which aligns with its mechanism of action requiring gut bacterial metabolism 2, 1
- The onset of action is typically 6-12 hours, making nighttime dosing ideal for morning bowel movements 2
Important Clinical Considerations
Dose Titration Strategy
- Begin with the lower dose (2 teaspoons/10 mL) and increase only if there is no response after several days 2
- In clinical trials, 83% of participants reduced their senna dose due to side effects, highlighting the importance of starting low 2
- The trial dose of 1 gram daily is higher than typically used in clinical practice, and most commercially available products contain 8-9 mg per tablet equivalent 2
Common Side Effects
- Abdominal pain and cramping may occur, particularly at higher doses 2
- Diarrhea is possible but less common with senna (31.8%) compared to bisacodyl (53.4%) at comparable doses 2
- Most adverse events occur during the first week of treatment 2
Duration of Use
- Senna is recommended for short-term or rescue therapy, though longer-term use (beyond 4 weeks) is probably appropriate based on clinical judgment 2
- Unlike bisacodyl, senna has demonstrated no evidence of tolerance development in pediatric studies, suggesting it may be safer for extended use 3