Senna 8.6 mg tablets are an over-the-counter stimulant laxative used for short-term relief of constipation. Each tablet contains 8.6 mg of sennosides, the active compounds derived from the senna plant, which work by irritating the lining of your large intestine to trigger muscle contractions that push stool through. Senna is also sometimes used to empty the bowels before surgery or medical procedures like a colonoscopy.
How Senna Tablets Work
When you swallow a senna tablet, your body breaks down the sennosides in your large intestine. These compounds stimulate the nerve endings in your colon wall, causing the muscles to contract more forcefully than they normally would. At the same time, senna reduces the amount of water your colon absorbs from stool, keeping it softer and easier to pass. The combination of stronger contractions and softer stool is what produces a bowel movement, typically 6 to 12 hours after you take the tablet. That’s why the label recommends taking it at bedtime, so it works overnight and produces a morning bowel movement.
Standard Dosing by Age
The starting dose for adults and children 12 and older is 2 tablets once a day. If needed, the dose can be increased up to a maximum of 4 tablets twice a day. Children aged 6 to 11 start with 1 tablet once a day, with a maximum of 2 tablets twice a day. For children 2 to 5, the starting dose is half a tablet once a day, up to 1 tablet twice a day. Children under 2 should not take senna without a doctor’s guidance.
Start with the lowest dose and increase only if you don’t get results. Most people find relief within a day or two at the starting dose.
What to Expect While Taking It
The most common side effect is mild abdominal cramping, which makes sense given that the drug is literally making your intestinal muscles contract harder than usual. Some people also experience nausea or loose stools, particularly at higher doses.
One thing that surprises people: senna can turn your urine a red-brown color. This is completely harmless and goes back to normal once you stop taking it. It’s just the sennosides being processed and excreted by your kidneys, not a sign of bleeding or a problem.
Why It’s Meant for Short-Term Use
Senna is designed as a temporary fix, not a daily habit. Using it for many weeks or months can cause your bowel to stop working properly on its own. Your colon essentially becomes dependent on the stimulation, making it harder to have a natural bowel movement without the drug.
Prolonged use also carries a more serious risk: electrolyte imbalance. Senna pulls water into your colon, and over time this can deplete important minerals like potassium, sodium, and magnesium. A severe imbalance can cause muscle spasms, twitching, and in rare cases, seizures. Ideally, you should only use senna for a few days at a time. If you find yourself needing it regularly, that’s worth a conversation with your doctor about the underlying cause of your constipation.
Interactions With Other Medications
Because senna can lower your potassium levels, it interacts with several common medications that affect the same mineral balance. Diuretics (water pills), steroid tablets like prednisolone, and heart medications like digoxin all deserve attention. The combination of senna and any of these drugs can push your electrolyte levels further out of balance. With digoxin specifically, low potassium makes the serious side effects of that heart medication more likely. If you take any of these, let your doctor know before using senna.
Pregnancy and Breastfeeding
Senna is occasionally used during pregnancy, and there’s no evidence it causes harm to the baby. That said, other types of laxatives have a longer safety track record in pregnancy, so those are generally recommended first. If you’re breastfeeding, only tiny amounts of sennosides pass into breast milk, and they’re unlikely to cause side effects in your baby.
Who Should Avoid Senna
Senna is not appropriate for everyone with constipation. You should avoid it if you have unexplained abdominal pain, signs of a bowel obstruction (severe bloating, vomiting, inability to pass gas), or inflammatory bowel conditions like Crohn’s disease or ulcerative colitis. In these situations, stimulating your colon more aggressively can make things significantly worse. If your constipation is new, severe, or accompanied by other symptoms, it’s worth figuring out what’s causing it before reaching for a stimulant laxative.