Sodium sulfate

Mechanism of action

The drug belongs to the group of laxatives that cause mechanical receptor irritation. Chemically, it is a decahydrate crystal hydrate ($Na_2SO_4 \cdot 10H_2O$).

After oral administration, Natrii sulfas is practically not absorbed in the gastrointestinal tract. Being in the intestinal lumen, it sharply increases osmotic pressure. This leads to delayed water absorption from the intestine. As a result, the volume of intestinal contents increases significantly, which causes strong stretching of the intestinal walls and irritation of mechanoreceptors. The reflex response to this irritation is a powerful stimulation of peristalsis and subsequent evacuation.

Pharmacodynamics

Unlike many other laxatives (e.g., plant-derived anthraglycosides), sodium sulfate acts totally — throughout the entire intestine, affecting both the small and large intestine.

The latent period of the drug is from 4 to 6 hours — this is exactly how long it takes for fluid accumulation, intestinal distension, and the development of a full laxative effect.

Indications for use

The main niche for prescribing saline laxatives is situations requiring rapid, complete, and radical bowel evacuation.

• Acute food poisoning: this is the primary indication. The drug not only physically removes toxins and poisons from the GI tract, but also prevents their further absorption into the systemic circulation due to high osmotic pressure.
• Preoperative preparation: used for thorough bowel cleansing before surgical interventions.
• Treatment of constipation: rarely used, exclusively as a single measure to relieve an acute condition.

Limitations and contraindications

The drug is strictly unsuitable for regular use.

• Limitations: Natrii sulfas is not used for chronic constipation of any etiology (alimentary, endocrine, neurogenic). For these purposes, other groups of drugs exist (e.g., disaccharides or bulk-forming agents).
• Absolute contraindication: intestinal obstruction. The administration of potent peristalsis stimulants in the presence of a mechanical obstacle in the GI tract will lead to severe complications.

Dosage form and administration rules

The drug is available as a powder. It is prescribed exclusively orally.

A single dose for an adult patient is 15–30 g (some regimens indicate 15–20 g). Before administration, the required amount of powder should be dissolved in half a glass of water.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Comparative characteristics of saline laxatives: sodium sulfate, magnesium sulfate, Karlsbad salt.
• Chemoreceptor-stimulating laxatives: synthetic (bisacodyl) and plant-based (senade, castor oil).
• Mechanism of action of osmotic laxatives based on disaccharides (lactulose).
• Agents increasing intestinal content volume (kelp, methylcellulose).
• Principles of pharmacotherapy for acute oral poisoning.

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