Senna (Senna alexandrina), known in Morocco as sana makki (سنا مكي), is one of the most requested plants in the herbalist shops of Fez, Marrakech and Casablanca. Renowned for its fast laxative action, senna is also one of the most misused medicinal plants: many people take it for long periods or to lose weight, when it should only be used occasionally and with proper guidance. This article reviews its composition, its real benefits, the dosage recommended by health authorities and the essential precautions.
What is senna (sana makki)?
Senna is a small shrub about 60 cm tall, belonging to the Fabaceae family (subfamily Caesalpinioideae). It has long, spreading branches bearing four to five pairs of leaflets, small yellow flowers and elongated pods containing around six seeds.
The word “senna” comes from Arabic. The plant is mainly grown in Nubia, Egypt, Sudan and India. The plants are cut twice a year, sun-dried, shelled and then shipped to market. In Moroccan herbalist shops you will find two forms: senna leaves (the most common) and senna pods (follicles), which are reputed to be slightly better tolerated.
Several botanical names refer to the same herbal drug: Cassia angustifolia, Cassia acutifolia, Cassia senna and Cassia lanceolata. All of them now refer to Senna alexandrina.
Composition and active compounds of senna
Senna’s activity is based on a well-identified family of molecules: the hydroxyanthracene derivatives, mainly sennosides A and B, anthraquinone glycosides concentrated in the leaves and pods.
- Sennosides A and B: the reference laxative compounds, measured in standardised preparations.
- Mucilages: they retain water and help soften the stool.
- Flavonoids and polyphenols: present in smaller amounts.
- Sugars and resins: responsible for some of the abdominal cramps seen at high doses.
The mechanism is now well described. Sennosides are not absorbed in the small intestine: they reach the colon, where the gut flora converts them into rhein (rhein anthrone). This molecule works in two complementary ways: it promotes the release of serotonin and histamine, which stimulates prostaglandin E2 and therefore peristaltic contractions; and it increases the activity of nitric oxide synthase, whose nitric oxide relaxes the smooth muscle fibres between contractions. The result: stool moves through faster. At the same time, sennosides reduce water reabsorption in the colon, which keeps the stool hydrated.
The benefits of senna
Unlike many traditional plants, senna does not have a broad range of uses: it has one main indication, recognised by health authorities, and a few related occasional uses.
1. Relieving occasional constipation
This is the indication recognised by the European Medicines Agency (EMA) and the WHO: the short-term treatment of occasional constipation. Senna is classed as a “stimulant” or “contact” laxative, as opposed to bulk-forming laxatives such as psyllium or flaxseed.
2. Fast, predictable action
The effect usually appears 6 to 12 hours after intake, which is why senna is recommended at bedtime for a bowel movement the next morning. This predictability is one of its main advantages over gentle laxatives, which can take several days to work.
3. Softening hard stools
By limiting water reabsorption in the colon, senna prevents the formation of hard, lumpy stools and makes bowel movements easier when they are painful. It is sometimes used for this purpose in cases of haemorrhoids or anal fissure, but always on medical advice.
4. Preparation for certain digestive examinations
Sennoside-based preparations are used in hospitals and clinics to empty the colon before a colonoscopy or abdominal imaging. This use is strictly prescription-only and has nothing to do with home use.
5. A long-standing traditional use
Senna has featured in the Arab-Islamic pharmacopoeia for centuries and was an ingredient of the “catholicum simple” in 18th-century Western pharmacopoeias. In Morocco, it is traditionally taken as an infusion, often combined with other digestive herbs to soften its bitterness and reduce cramping.
One point needs to be made clearly: senna is not a slimming product. The weight loss seen after taking it is a loss of water and intestinal content, not of body fat. Using it for this purpose is both ineffective and risky.
How to use senna and dosage
The golden rule with senna is simple: the lowest dose that produces a soft stool, for the shortest possible time.
- Reference dose (EMA): a preparation providing the equivalent of 15 to 30 mg of hydroxyanthracene derivatives, calculated as sennoside B, taken once in the evening.
- Frequency: no more than once a day, never several times during the day.
- Duration: one week maximum without medical advice. Both the EMA and ESCOP stress strictly short-term use.
- Infusion: in the absence of a standardised product, the traditional method is to steep a small amount of dried leaves in hot water for 10 minutes. Be careful: the sennoside content of a homemade infusion is unpredictable, hence the risk of overdose.
- Hydration: drink plenty of fluids during use, as the laxative effect causes fluid loss.
If constipation lasts longer than a few days, or if it is chronic, senna is not the right answer. Bulk-forming laxatives and mucilages (psyllium, flaxseed, mallow) are better suited to regular use, alongside a fibre-rich diet and daily physical activity.
Precautions, side effects and contraindications
Senna is an active plant, and its safety profile calls for rigour. It is probably the plant most affected by misuse in self-medication.
Contraindications
- Intestinal obstruction or stenosis, colonic atony, ileus.
- Chronic inflammatory bowel diseases (Crohn’s disease, ulcerative colitis), appendicitis.
- Abdominal pain of unknown origin, persistent nausea or vomiting.
- Severe dehydration with electrolyte loss.
- Children under 12.
- Pregnancy and breastfeeding: not recommended as a precaution.
- Chronic constipation, unless on medical advice.
Possible side effects
- Abdominal cramps and pain, nausea, diarrhoea — the most common, often linked to overdose.
- Yellow or reddish discolouration of the urine, which is harmless.
- Hypersensitivity reactions.
- With prolonged use: irritation of the colonic lining, melanosis coli, colonic atony (laxative dependence), and reported liver problems.
- Hypokalaemia (low potassium) with excessive use, with a risk of heart rhythm disorders.
Drug interactions
The main risk is the combined effect of potassium-lowering substances. Caution is needed with diuretics, corticosteroids, liquorice, and above all cardiac glycosides (digoxin) and antiarrhythmics, whose toxicity increases when potassium drops. Faster transit can also reduce the absorption of other medicines taken at the same time. If you are on long-term treatment, ask your pharmacist for advice before using senna.
Note: at normal doses and over short periods, the available data are reassuring. A study in older adults (the population most sensitive to potassium loss) found no change in exchangeable potassium stores after six months at the equivalent of 20 mg of sennosides per day. The problem lies in misuse, not in properly supervised use.
FAQ: your questions about senna
How long does senna take to work?
Usually 6 to 12 hours. That is why it is taken in the evening, for an effect on waking. If there is no effect after 24 hours, do not double the dose; reassess the situation instead.
Can I take senna every day?
No. Prolonged daily use exposes you to colonic atony, laxative dependence and electrolyte imbalances. The recommended duration without medical advice is one week maximum.
Does senna help you lose weight?
No. The drop you see on the scale is a loss of water and intestinal content, which is regained immediately. Using senna as a slimming product is a bad idea in terms of both effectiveness and safety.
In summary
Senna is a powerful plant-based laxative, effective and fast-acting against occasional constipation thanks to its sennosides. Its strength is also its limit: it is not a wellness tea to drink daily, but an active plant to be reserved for occasional situations, at a low dose, for one week at most. For long-term support of bowel regularity, fibre and mucilages remain the best option.
Further reading
- Botanical and pharmacological profile of Senna alexandrina (Wikipedia)
- Psyllium (Ispaghula): benefits, dosage and precautions
- Flaxseed: benefits, dosage and precautions
- Mallow (Khoubiza): benefits, dosage and precautions
This article is for information only and does not replace medical advice. Ask your doctor or pharmacist before using senna, especially if you are on medication, have a digestive condition, or are pregnant or breastfeeding.
