Mechanism of Action
The drug belongs to the class of laxatives that cause mechanical receptor stimulation. Chemically, it is a decahydrate crystal hydrate ($Na_2SO_4 \cdot 10H_2O$).
Following oral administration, Natrii sulfas is virtually unabsorbed in the gastrointestinal tract. Remaining within the intestinal lumen, it sharply increases osmotic pressure. This prevents water absorption from the bowel. As a result, the volume of intestinal contents increases significantly, causing marked distention of the intestinal walls and stimulation of mechanoreceptors. The reflex response to this stimulation is a powerful increase in peristalsis followed by evacuation.
Pharmacodynamics
Unlike many other laxatives (e.g., plant-derived anthraglycosides), sodium sulfate acts systemically across the entire gut, affecting both the small and large intestines.
The latent period of the drug ranges from 4 to 6 hours — this is the time required for fluid accumulation, bowel distention, and the development of a full laxative effect.
Indications for Use
The primary clinical niche for saline laxatives is situations requiring rapid, complete, and radical bowel evacuation.
- Acute food poisoning: This is the main indication. The drug not only physically removes toxins and poisons from the GI tract but also, due to its high osmotic pressure, prevents their further absorption into the systemic circulation.
- Preoperative preparation: Used for thorough bowel cleansing prior to surgical procedures.
- Constipation management: Rarely used, exclusively as a single-dose measure to relieve acute conditions.
Limitations and Contraindications
The drug is strictly unsuitable for regular, long-term use.
- Limitations: Natrii sulfas is not indicated for chronic constipation of any etiology (alimentary, endocrine, neurogenic). Other classes of drugs exist for these purposes (e.g., disaccharides or bulk-forming agents).
- Absolute Contraindication: Intestinal obstruction. Administering potent peristalsis stimulators in the presence of a mechanical obstruction in the GI tract leads to severe complications.
Formulation and Administration
The drug is available as a powder. It is administered exclusively via the oral route.
An adult single dose is 15–30 g (some regimens recommend 15–20 g). Before administration, the required amount of powder must be dissolved in half a glass of water.