SENNA TABLETS

Indications

• Constipation
• Bowel preparation for diagnostic procedures

Dosage

Children: For children aged 6 to 12 years, the recommended dose is 5 to 10 mg at bedtime. For those over 12 years, the adult dosage applies. Always refer to the BNF for Children for specific dosing guidance.

Adults: The usual adult dose for constipation is 7.5 to 15 mg of sennosides taken at bedtime. For bowel preparation, higher doses may be required as directed by a healthcare provider.

Mechanism of action

Sennoside A and B are metabolized by gut bacteria into rheinanthrone, which increases cyclooxygenase 2 (COX2) expression in macrophage cells, leading to elevated levels of prostaglandin E2 (PGE2). This increase in PGE2 decreases aquaporin 3 expression in the mucosal epithelial cells of the large intestine, reducing water reabsorption and increasing fecal water content, resulting in a laxative effect. Rheinanthrone also stimulates peristalsis in the large intestine, although the precise mechanism is not fully understood. Additionally, another metabolite, rhein, may activate submucosal acetylcholinergic neurons, enhancing chloride and prostaglandin secretion, thereby promoting water influx into the intestinal lumen.

Pharmacodynamics

Sennosides stimulate intestinal peristalsis and enhance fecal water content, which collectively increases the motility of feces through the large intestine, facilitating bowel movements.

Pharmacokinetics

Sennosides are absorbed in the intestine and then metabolized by gut bacteria into active metabolites. The onset of action is typically within 6 to 12 hours after oral administration, depending on the formulation. The metabolites, particularly rheinanthrone, exert their effects locally in the large intestine, with minimal systemic absorption.

Contra-indications

• Intestinal obstruction
• Severe dehydration
• Appendicitis
• Abdominal pain of unknown origin
• Ulcerative colitis
• Crohn's disease
• Severe abdominal conditions

Adverse effects

• Abdominal cramps
• Diarrhea
• Nausea
• Vomiting
• Electrolyte imbalances
• Discoloration of urine

Interactions

• May enhance the effects of other laxatives
• May reduce the effectiveness of certain medications due to altered gastrointestinal motility

Precautions

• Use with caution in patients with known gastrointestinal disorders
• Long-term use may lead to dependence
• Monitor for signs of electrolyte imbalance
• Not recommended for use in children under 12 years without medical advice

Pregnancy

Use during pregnancy should be avoided unless specifically advised by a healthcare provider, as safety has not been established.

Breast-feeding

Limited data available; caution is advised as sennosides may be excreted in breast milk.

Storage

Store in a cool, dry place, away from direct sunlight and out of reach of children.

Formulations

• Oral tablets
• Syrup
• Powder for oral solution

Dosage

Children: Paediatric dosing should also be determined based on the specific formulation and clinical context. Refer to appropriate paediatric guidelines.

Adults: Dosage would depend on the specific formulation and clinical scenario. Refer to established guidelines for specific dosing.

Mechanism of action

The mechanism of action would depend on the specific formulation or active ingredients referred to as 'total'. For example, in the context of total parenteral nutrition, it provides essential nutrients (carbohydrates, proteins, fats, vitamins, and minerals) directly into the bloodstream, bypassing the gastrointestinal tract.

Pharmacodynamics

Pharmacodynamics would vary widely based on the specific active ingredients within the formulation. In the case of total parenteral nutrition, its pharmacodynamics involve the absorption of macronutrients and micronutrients into the body for metabolic processes.

Pharmacokinetics

Pharmacokinetics would also vary based on the specific components. For example, when discussing total parenteral nutrition, the components are absorbed into the bloodstream, metabolized by the liver, and utilized by various tissues in the body. The elimination of waste products occurs primarily through the kidneys.

Mechanism of action

Sennoside A and B, the components of senna, are metabolized by gut bacteria into the active metabolite rheinanthrone [DB13175]. Rheinanthrone [DB13175] appears to increase cyclooxegenase 2 (COX2) expression in macrophage cells leading to an increase in prostaglandin E2 (PGE2). This increase in PGE2 is associated with a decrease in aquaporin 3 expression in mucosal epithelial cells of the large intestine. A decrease in aquaporin 3 expression likely produces the laxative effect by restricting water reabsorption by the large intestine thereby increasing fecal water content. The exact mechanism by which rheinanthrone increases COX2 expression is unknown. Rheinanthrone [DB13175] also stimulates peristalsis in the large intestine although the mechanism behind this effect is unknown. Rhein [DB13174], another active metabolite is thought to excite submucosal acetylcholinergic neurons resulting in increased chloride and prostaglandin secretion. The movement of chloride ions into the large intestine would also help to draw water into the lumen.

Pharmacodynamics

Senna stimulates peristalsis and increases fecal water content to increase motility of feces through the large intestine.