Senna

Generic Name: Senna (also known as sennosides, senna glycosides)
Botanical Source: Senna alexandrina (also previously classified as Cassia angustifolia)

Drug Class: Stimulant laxative (anthraquinone glycoside class)
Pharmaceutical Category: Over-the-counter (OTC) herbal and non-herbal laxative
Formulations: Oral tablets, chewable tablets, syrup, granules, tea, liquid extracts
Routes of Administration: Oral, Rectal (occasionally in compounded enemas)

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Therapeutic Indications and Clinical Use

Senna is primarily used as a short-term treatment for constipation, especially when rapid evacuation of the bowel is necessary. It is also widely used in preparation for certain diagnostic procedures, including colonoscopy and abdominal radiologic exams.

Approved and Common Clinical Uses:

1. Occasional constipation

   • Effective in producing bowel movement within 6–12 hours after oral administration

2. Bowel evacuation prior to colonoscopy or surgery

   • Used in combination with other agents for complete colon cleansing

3. Neurogenic or opioid-induced constipation

   • Often prescribed alongside stool softeners like docusate sodium

4. Postpartum or postoperative bowel management

   • Useful in patients where straining is contraindicated

5. Functional constipation in elderly or immobile patients

6. Irritable Bowel Syndrome (IBS-C)

   • Used occasionally under physician supervision

Off-Label Uses:

• Part of weight loss regimens (unsafe and not recommended)

• In herbal detox products and teas (not medically approved)

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Mechanism of Action

Senna contains sennosides A and B, which are anthraquinone glycoside compounds. These compounds are prodrugs that exert their laxative effect via two main mechanisms:

1. Stimulation of colonic motility:

   • Sennosides are hydrolyzed by colonic bacteria into active metabolites (rhein anthrone), which directly stimulate the myenteric plexus of the colon, increasing peristaltic contractions and bowel motility.

2. Inhibition of water and electrolyte absorption in the colon:

   • Active metabolites reduce reabsorption of water and sodium, resulting in increased fluid content and volume of feces.

Note: The laxative effect typically begins 6–12 hours after oral ingestion and 0.5–2 hours after rectal use.

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Dosage and Administration

Adults:

• Constipation (oral tablets or syrup):

  • 7.5 mg to 15 mg of sennosides once daily at bedtime

  • Max dose: up to 34.4 mg/day if needed under supervision

• Bowel cleansing before procedures:

  • 20–40 mg in split doses the day prior, often with other agents like polyethylene glycol or bisacodyl

Children (under medical supervision):

• 6–12 years: 8.6 mg once daily, max 17.2 mg/day

• 2–6 years: 3.75–7.5 mg/day

• Not recommended for use in children <2 years

Duration of Use:

• Short-term only (maximum 7 days without physician guidance)

• Prolonged use can cause dependence and colonic dysfunction

Administration Tips:

• Take at bedtime to produce a bowel movement in the morning

• Adequate hydration is essential

• Tablets and syrups should be swallowed with water

• Herbal teas and powders should be steeped as directed, usually 5–10 minutes

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Pharmacokinetics

• Absorption: Not systemically absorbed in active form

• Activation: Hydrolyzed by colonic bacteria into rhein anthrone

• Onset of Action:

  • Oral: 6–12 hours

  • Rectal: 0.5–2 hours

• Excretion: Primarily fecal, small amounts renally eliminated

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Contraindications

• Known hypersensitivity to senna or anthraquinones

• Intestinal obstruction or stenosis

• Acute inflammatory intestinal conditions (e.g., Crohn’s disease, ulcerative colitis during flares)

• Appendicitis or symptoms suggestive of appendicitis

• Undiagnosed abdominal pain

• Severe dehydration

• Chronic use for weight loss

• Electrolyte depletion (e.g., hypokalemia)

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Warnings and Precautions

• Electrolyte imbalance: Chronic use can lead to hypokalemia, hypocalcemia, and sodium depletion

• Laxative dependency: Prolonged misuse may impair normal bowel function

• Melanosis coli: Long-term use can cause pigmentation of the colon mucosa (benign and reversible)

• Rectal bleeding or failure to respond to therapy: Discontinue and investigate underlying cause

• Renal impairment: Caution due to potential fluid/electrolyte loss

• Pregnancy: Short-term use may be acceptable but consult healthcare provider

• Breastfeeding: Metabolites appear in breast milk; limited clinical relevance but caution advised

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Adverse Effects

Common (1–10%):

• Abdominal cramps

• Diarrhea

• Nausea

• Flatulence

Less Common/Serious (<1%):

• Hypokalemia

• Dehydration

• Electrolyte disturbances

• Melanosis coli

• Allergic skin reactions (rash, pruritus)

• Protein-losing enteropathy (rare with long-term abuse)

Signs of Overdose:

• Severe diarrhea

• Abdominal pain

• Fluid and electrolyte loss

• Tetany (from hypocalcemia)

• Muscle weakness (from hypokalemia)

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Drug Interactions

1. Cardiac glycosides (e.g., digoxin):

   • Hypokalemia from senna can enhance digoxin toxicity

2. Diuretics and corticosteroids:

   • Additive potassium loss

3. Antiarrhythmics (e.g., quinidine, amiodarone):

   • Increased arrhythmia risk with electrolyte disturbance

4. Warfarin and anticoagulants:

   • Excessive diarrhea may alter vitamin K absorption and bleeding risk

5. Licorice root:

   • Potentiates potassium loss

6. Other laxatives:

   • Additive effects; increase risk of side effects

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Monitoring Parameters

• Monitor bowel movement frequency and consistency

• Watch for signs of dehydration (dry mouth, dizziness, low urine output)

• Monitor serum potassium in elderly or chronic users

• Assess abdominal pain and rule out surgical abdomen before starting

• Evaluate necessity beyond 7 days of use

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Pregnancy and Lactation

• Pregnancy Category C (US)

  • Use short-term and only when necessary

  • No evidence of teratogenicity at therapeutic doses

• Breastfeeding:

  • Senna metabolites may appear in breast milk in small quantities

  • Generally considered compatible by WHO and AAP, but monitor infants for diarrhea

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Use in Special Populations

• Elderly:

  • Increased sensitivity to fluid and electrolyte shifts; start at lower dose

• Pediatric:

  • Only under pediatrician guidance; never for infants <2 years

• Renal impairment:

  • Risk of fluid/electrolyte imbalance; monitor closely

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Counseling Points for Patients

• Use only for short-term relief of constipation

• Do not exceed recommended dose or duration

• Take with plenty of water

• Expect a bowel movement in 6–12 hours after a dose

• Discontinue if rectal bleeding or no bowel movement occurs

• Avoid chronic use for weight control

• Maintain a diet high in fiber and fluids to prevent dependency

• Contact a healthcare provider if constipation persists beyond one week

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Abuse Potential and Public Health Concerns

• Senna-containing products are sometimes misused for weight loss and "detox" regimens

• Chronic misuse may result in:

  • Dependency

  • Colonic atony

  • Serious electrolyte disturbances

  • Renal dysfunction

• Regulatory agencies warn against unsupervised long-term use, especially in combination with other stimulant laxatives

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Global Availability and Regulatory Classification

• Widely available OTC globally

• Found in both pharmaceutical-grade preparations and herbal/ayurvedic products

• Regulated as a medicine in EU and US when labeled for laxative use

• Present in combination products (e.g., senna + docusate, senna + psyllium)

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Common Brand Names

• UK: Senokot, Senna Tablets BP

• USA: Ex-Lax, Senokot, Fletcher’s Castoria, Nature’s Remedy

• Middle East/India: Kayam Churna (traditional), Herbomint Senna

• Natural Products: Smooth Move Tea (contains senna), Herbal Laxatives

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Storage and Stability

• Store at room temperature (15–25°C)

• Keep away from moisture and direct sunlight

• Keep out of reach of children due to risk of overdose