Senna Dosage for Adult Constipation

Start with 8.6-17.2 mg (1-2 tablets) of senna taken once daily at bedtime, and titrate upward based on response and tolerability. 1, 2

Initial Dosing Strategy

Begin with 8.6-17.2 mg daily (equivalent to 1-2 standard tablets) taken at bedtime to allow the 6-12 hour onset of action to produce a morning bowel movement 1, 2
For liquid formulations, the FDA-approved dosing is 2-3 teaspoons (10-15 mL) once daily for adults, with a maximum of 3 teaspoons (15 mL) twice daily 3
The lower starting dose is critical because clinical trials using 1 gram daily found that 83% of participants had to reduce their dose due to side effects, indicating this higher dose is poorly tolerated 1

Titrate upward only after several days if inadequate response, as the American Gastroenterological Association emphasizes starting low and increasing gradually 1, 2
The maximum recommended dose is generally 4 tablets twice per day, though no clear maximum has been established in guidelines 1
In palliative care settings for patients with severe constipation and limited life expectancy, higher doses of 2-3 tablets 2-3 times daily may be appropriate, targeting one non-forced bowel movement every 1-2 days 1, 2

Senna significantly increases complete spontaneous bowel movements by 7.60 per week compared to placebo (95% CI 5.90-9.30), with moderate strength of evidence 1
Response rates are substantially higher with senna versus placebo (RR 5.25,95% CI 2.05-13.47) 1
Both senna and magnesium oxide showed 69% response rates for overall symptom improvement compared to 12% with placebo in a randomized controlled trial 4

Common side effects include abdominal cramping, diarrhea, and abdominal pain, particularly at higher doses 1, 2
Severe diarrhea can lead to significant fluid and electrolyte depletion, particularly potassium, which can cause life-threatening cardiac arrhythmias 1
Monitor for hypokalemia in patients on QT-prolonging medications, those with cardiac conditions, or patients taking other medications affecting potassium levels 1
Contraindicated in ileus, intestinal obstruction, severe dehydration, or acute inflammatory bowel conditions 1, 2

Not recommended during pregnancy due to potential weak genotoxic effects observed in animal studies 1
Antibiotics may decrease senna's efficacy by affecting colonic bacteria that metabolize sennosides to active compounds 1
Senna is present in many laxative teas where precise dosing is difficult to calculate 1
May be too strong for overtly weak or debilitated patients 2

While clinical trials evaluated 4-week treatment periods, longer-term use is appropriate for chronic constipation management, though data on extended use tolerance are limited 1, 2
The American Gastroenterological Association conditionally recommends senna over no treatment for chronic idiopathic constipation (low certainty of evidence) 1, 2

If senna fails at optimal dosing, escalate to prescription secretagogues such as linaclotide, plecanatide, lubiprostone, or prucalopride 5
Before escalating, rule out mechanical obstruction or impaction, discontinue non-essential constipating medications, and treat reversible causes (hypercalcemia, hypokalemia, hypothyroidism, diabetes) 5