Senna Pharmacology

Real Life Pharmacology - Pharmacology Education for Health Care Professionals

Eric Christianson, PharmD; Pharmacology Expert and Clinical Pharmacist

Education, Health & Fitness, Medicine

5 • 716 Ratings

🗓️ 18 September 2025

⏱️ 14 minutes

🔗️ Recording | iTunes | RSS

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Summary

Senna is a stimulant laxative. Its pharmacological activity comes from natural compounds called sennosides. Metabolites act locally in the colon to stimulate peristalsis, thereby accelerating bowel movements. While osmotic laxatives are generally considered first-line laxative agents, this makes senna a useful alternative for the short-term treatment of constipation.

The pharmacokinetics of senna are unique in that its onset of action typically takes 6 to 12 hours after oral administration, reflecting the time required for colonic bacteria to metabolize sennosides into active compounds. This delayed onset makes senna better suited for bedtime dosing when overnight relief is desired.

Although senna is effective, its use carries potential adverse effects. Common side effects include abdominal cramping, diarrhea, and, rarely, electrolyte disturbances such as hypokalemia. Chronic or excessive use can lead to dependency and possibly melanosis coli, a benign but visible pigmentation of the colon lining.

Drug interactions may occur, particularly with medications affected by potassium levels, such as digoxin or diuretics. For these reasons, senna is generally recommended for short-term use, with emphasis on evaluating underlying causes of constipation before long-term therapy is considered.

Transcript

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0:00.0	Hey, all, welcome back to the real-life pharmacology podcast. I'm your host, pharmacist, Eric Christensen.
0:05.4	Thank you so much for listening today. As always, go get that free PDF. It's 31 pages. It's a nice
0:12.2	little study guide, good refresher on the top 200 medications. I share some of the most important things
0:18.6	you're going to see in practice as well as a lot of things that are going to show up on your board exams, pharmacology exams as well.
0:25.5	So again, go get that. RealLife Pharmacology.com. Simply an email is all it requires to get that. And then we'll get you updates on. we've got new podcasts and other content available as well
0:39.5	all right let's get into the drug of the day today and that is senna often referred to as
0:47.8	senicides as well uh lots of different brand names uh this is a stimulant laxative. So anything over the counter that you see the word
1:01.2	laxative or stimulant associated with it. If you look at the back, there's a good chance it might have
1:08.5	Sena in it or potentially bisacal as well as another example of a
1:13.5	stimulant laxative. So again, Sena is probably the most common name you're going to see there.
1:19.7	There are different strengths, dosage forms with this medication. One I see in my geriatric
1:27.3	space quite a bit is Senna S. So that actually includes
1:30.7	a stool softener. That's what the additional S is for at the end. So that's going to include
1:37.3	docusate with that medication as well. All right. So mention the class. Sena is a stimulant laxative. It directly stimulates colonic peristulses. So basically, that movement of the colon and the forceful contraction that allows a person to defecate and go to the
2:05.2	bathroom. So this medication is obviously used for constipation. It's important. There definitely
2:14.0	needs to be some patient education. Ideally, with SENA, it is available over the counter,
2:18.5	so patients can just go grab it without any counseling or anything like that.
2:23.5	But it's always good to keep tabs on patients if they are purchasing a laxative,
2:30.7	see if you can get some information from them.
2:34.1	Are they having any high risk symptoms?
2:37.1	You know, are they having some stomach pain, nausea, vomiting?
2:41.9	Are they having blood in the stool?
	...

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