Senna
- Class: Stimulant laxative
- Used for: constipation
- Say it: SEN-uh
- Forms: tablet, oral liquid
SENNA SENDS it on its way overnight. Taken at bedtime, it works by breakfast.
Gut bacteria have to activate it first, and that takes 8 to 12 hours — which is exactly why bedtime is the right time to take it.
Senna is a plant-derived stimulant that gut bacteria must activate first. That conversion takes 8-12 hours, which is exactly why a bedtime dose produces a result after breakfast.
Side effects
Common: stomach cramps, diarrhea, discolored urine
Serious: salt loss with overuse
Typical dose
7.5–15 mg at night
Taken at bedtime so the effect arrives after breakfast rather than in the middle of the night.
Check yourself
Why is senna started at the same time as a strong opioid?
- Opioid constipation is near-universal and does not wear off with tolerance
- Senna prevents opioid dependence
- It improves the analgesic effect
- It stops opioid-induced nausea
Show answer
A. Opioid constipation is near-universal and does not wear off with tolerance
Tolerance develops to the drowsiness and nausea of opioids but not to their effect on gut motility. The constipation therefore persists for as long as the opioid does, which is why the laxative is co-prescribed rather than held in reserve.
See it, don't memorize it
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