Usage
Dibasic sodium phosphate is primarily used as a saline laxative for bowel cleansing before medical procedures such as colonoscopies. It is also used to treat constipation. It can also be administered intravenously as an electrolyte replenisher, specifically to address hypophosphatemia (low phosphorus levels). It falls under the pharmacological classifications of laxative, cathartic, and electrolyte replenisher.
The mechanism of action for oral administration involves increasing the amount of water in the intestine. This softens the stool and induces bowel movements. For intravenous administration, it directly replenishes phosphate levels in the blood, crucial for various physiological functions.
Alternate Names
- Disodium hydrogen phosphate
- Disodium phosphate
- DSP
- Sodium phosphate dibasic anhydrous
- Sodium phosphate dibasic dihydrate
- Sodium phosphate dibasic heptahydrate
- Sodium hydrogen phosphate
Brand names include OsmoPrep, Visicol, and Fleet Phospho-Soda (oral); and Fleet Enema and Pedia-Lax Enema (rectal).
How It Works
Pharmacodynamics: Orally, dibasic sodium phosphate acts as an osmotic laxative, drawing water into the bowel lumen, increasing intraluminal pressure, and stimulating peristalsis. Intravenously, it directly increases serum phosphate levels, vital for bone metabolism, energy production, and acid-base balance.
Pharmacokinetics: Oral absorption is minimal. When administered orally for bowel preparation, only about 15% of the phosphate is absorbed, while the remainder is eliminated through the bowels. Intravenously, it directly enters the bloodstream. Excess phosphate and sodium are eliminated renally.
Dosage
Standard Dosage
Adults:
- Oral (Bowel Cleansing): Varies depending on the product and specific bowel preparation regimen. Common regimens include:
- OsmoPrep: 20 tablets with 8 oz of water every 15 minutes the evening before the procedure, followed by 12 tablets the day of the procedure 3-5 hours prior.
- Visicol: Multiple dosing regimens exist. Consult specific product information.
- Intravenous (Hypophosphatemia): Dose and infusion rate are individualized based on patient needs and serum phosphorus levels.
Children:
- Oral: For children older than 5 years for bowel cleansing, dosing is determined by the physician and depends on the product. Rectal use is possible for children 2 years and older following the specific product information. Use is not recommended in children younger than 2 years.
- Intravenous: Pediatric dosing should be carefully determined and monitored by a physician based on patient needs and serum phosphorus levels. Pediatric patients have an elevated risk for phosphate toxicity.
Special Cases:
- Elderly Patients: Dose adjustments may be necessary due to potential for decreased renal function. Electrolyte levels should be monitored.
- Patients with Renal Impairment: Dose reduction or avoidance may be required. Close monitoring of electrolyte levels is necessary.
- Patients with Hepatic Dysfunction: Caution should be exercised, although dose adjustment is not usually necessary.
- Patients with Comorbid Conditions: Use with caution in patients with heart failure, hypertension, or on sodium-restricted diets.
Clinical Use Cases
- Intubation, Surgical Procedures, Mechanical Ventilation, Intensive Care Unit (ICU) Use: Intravenous administration for the correction of hypophosphatemia.
- Emergency Situations: Intravenous administration for severe hypophosphatemia and related complications.
Side Effects
Common Side Effects
- Nausea, vomiting, abdominal pain/cramping, bloating, diarrhea, dizziness, headache.
Rare but Serious Side Effects
- Acute phosphate nephropathy, renal failure, seizures, cardiac arrhythmias, electrolyte imbalances (hypernatremia, hyperphosphatemia, hypocalcemia, hypokalemia), allergic reactions.
Contraindications
- History of acute phosphate nephropathy
- Gastrointestinal obstruction
- Gastric bypass or stapling surgery
- Bowel perforation
- Toxic colitis
- Toxic megacolon
- Hypernatremia
- Conditions associated with high phosphorus or low calcium levels
Drug Interactions
- Medications affecting renal function (ACE inhibitors, ARBs, diuretics, NSAIDs).
- Calcium channel blockers.
- Lithium.
- Aluminum-containing antacids.
- Other medications containing sodium or phosphorus.
Pregnancy and Breastfeeding
- Pregnancy: Use only if clearly needed. FDA Pregnancy Category C. Risk of fetal harm is not established.
- Breastfeeding: Sodium and phosphate are present in breast milk. Caution is advised. Consider expressing and discarding breast milk for 24 hours after administration of oral sodium phosphate for bowel cleansing.
Drug Profile Summary
- Mechanism of Action: Osmotic laxative (oral), electrolyte replenisher (IV).
- Side Effects: Nausea, vomiting, diarrhea, abdominal cramping, electrolyte imbalances, rarely acute phosphate nephropathy.
- Contraindications: GI obstruction, renal failure, hypernatremia.
- Drug Interactions: Drugs affecting renal function, calcium channel blockers, lithium.
- Pregnancy & Breastfeeding: Use with caution.
- Dosage: Varies depending on indication and route of administration. See dosage section for details.
- Monitoring Parameters: Serum electrolytes (sodium, phosphate, calcium, potassium), renal function, cardiac function.
Popular Combinations
Often used alone. Intravenous formulations may be combined with other electrolytes as needed.
Precautions
- Monitor fluid and electrolyte balance.
- Assess renal function.
- Use cautiously in patients with cardiovascular disease.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Dibasic sodium phosphate?
A: The dosage varies considerably depending on the indication (bowel cleansing, constipation, or electrolyte replenishment), route of administration (oral, rectal, or intravenous), patient age, and specific product formulation. Refer to the Dosage section above and consult specific product information for detailed instructions.
Q2: How does dibasic sodium phosphate work as a laxative?
A: It works by drawing water into the intestines, softening the stool and increasing pressure, which stimulates bowel movements.
Q3: What are the serious side effects of dibasic sodium phosphate?
A: Rare but serious side effects include dehydration, electrolyte imbalances (such as high phosphate and low calcium levels), kidney problems (including acute phosphate nephropathy), and heart rhythm abnormalities.
Q4: Who should not take dibasic sodium phosphate?
A: Individuals with certain conditions, including kidney disease, bowel obstruction, heart failure, and electrolyte imbalances, should not take this medication.
Q5: Can I take dibasic sodium phosphate while pregnant or breastfeeding?
A: Use during pregnancy or breastfeeding should be discussed with a physician. It should only be used if clearly needed.
Q6: What are the signs of an allergic reaction to dibasic sodium phosphate?
A: Allergic reactions are rare, but signs may include rash, itching, swelling (especially of the face, tongue, or throat), severe dizziness, and trouble breathing. Seek immediate medical attention if these occur.
Q7: What should I do if I miss a dose of dibasic sodium phosphate for bowel preparation?
A: Contact your physician for instructions. Do not double the dose. The timing of bowel preparation is critical for the procedure.
Q8: Can I take dibasic sodium phosphate with other medications?
A: Some medications can interact with dibasic sodium phosphate. Inform your doctor about all other medications, including over-the-counter drugs and supplements, that you are taking.
Q9: How should dibasic sodium phosphate be stored?
A: Store at room temperature away from moisture and heat. Refer to the specific product packaging for detailed storage instructions.
Q10: Are there any dietary restrictions when taking dibasic sodium phosphate for bowel cleansing?
A: Yes. You will generally need to follow a clear liquid diet for a specified period before the procedure. This may include clear broth, plain gelatin, popsicles, and certain juices without pulp. Your physician will provide specific instructions.
