Usage
Urea is prescribed for the management of several medical conditions, primarily those associated with elevated intracranial or intraocular pressure, and as an osmotic diuretic to promote water excretion. It also finds use in the topical treatment of certain skin conditions (e.g., xerosis, ichthyosis, onychomycosis) and as a medical food for managing hyponatremia.
It can be classified as an osmotic diuretic, and in some formulations, a medical food.
The primary mechanism of action is through osmotic diuresis. It elevates the osmolarity of the blood, creating an osmotic gradient that draws water out of tissues, including the brain and eyes, and promotes its excretion by the kidneys. In hyponatremia management, urea normalizes serum sodium levels by inducing osmotic excretion of free water.
Alternate Names
Carbamide
Brand Names: Ure-Na (oral powder), various generic formulations for intravenous and topical use.
How It Works
Pharmacodynamics: Urea exerts its effects primarily by increasing the osmotic pressure of body fluids. In the brain and eye, this action reduces fluid volume and pressure. As a diuretic, urea increases urine output by raising the osmotic pressure within the renal tubules, impeding water reabsorption.
Pharmacokinetics:
- Absorption: Oral urea is readily absorbed from the gastrointestinal tract.
- Metabolism: Minimally metabolized.
- Elimination: Primarily excreted by the kidneys through glomerular filtration, with some contribution from tubular secretion.
Mode of Action: Urea does not bind to specific receptors or inhibit enzymes. Its therapeutic effect stems solely from its osmotic properties. It does not directly modulate neurotransmitters.
Elimination Pathways: Predominantly renal excretion.
Dosage
Standard Dosage
Adults:
- Osmotic Diuresis/Intracranial Pressure Reduction: 1 to 1.5 g/kg as a 30% solution in 10% invert sugar or 5-10% dextrose, infused intravenously at a rate not exceeding 4 mL/min. Maximum: 120 g or 1.5 g/kg daily. As an oral diuretic: 20g 2-5 times/day.
- Hyponatremia (Medical Food): 15 to 60 g daily, orally. Mix each 15 g dose with 90 to 120 mL of water or juice.
Children:
- Osmotic Diuresis/Intracranial Pressure Reduction: 0.5-1.5g/kg (children >2 years), 0.1g/kg may be sufficient (children <2 years). Oral diuretic: 0.8 g/kg or 25 g/m2 in 24 hours, divided into 3 doses daily.
Special Cases:
- Elderly Patients: Initiate with lower doses and titrate cautiously, monitoring renal function closely.
- Patients with Renal Impairment: Use cautiously and with dosage reductions in renal impairment. Contraindicated in severe renal dysfunction.
- Patients with Hepatic Dysfunction: Use cautiously.
Clinical Use Cases
- Intubation/Surgical Procedures/Mechanical Ventilation/ICU Use: Dose as per the indication (e.g., intracranial pressure management).
- Emergency Situations: Dose as per the indication.
Dosage Adjustments:
Adjust dosage based on renal function, patient’s clinical condition, and electrolyte balance.
Side Effects
Common Side Effects
Headache, nausea, vomiting, dehydration.
Rare but Serious Side Effects
Syncope, bradycardia, extravasation leading to skin necrosis, hypernatremia.
Long-Term Effects
None specifically associated with short-term use.
Adverse Drug Reactions (ADR)
Extravasation leading to tissue necrosis.
Contraindications
Severe renal impairment, marked dehydration, active intracranial bleeding, liver failure.
Drug Interactions
No significant drug interactions have been reported.
Pregnancy and Breastfeeding
Use cautiously during pregnancy, and only if clearly needed. Its presence in breast milk and potential effects on the neonate are not well established.
Drug Profile Summary
- Mechanism of Action: Osmotic diuresis.
- Side Effects: Headache, nausea, vomiting, syncope, hypernatremia.
- Contraindications: Severe renal impairment, dehydration, active intracranial bleeding, liver failure.
- Drug Interactions: No significant interactions.
- Pregnancy & Breastfeeding: Use cautiously if clearly needed.
- Dosage: Varies depending on the indication; see dosage section.
- Monitoring Parameters: Serum sodium, blood urea nitrogen, creatinine, urine output, and vital signs.
Popular Combinations
No commonly used drug combinations specifically for urea administration.
Precautions
Monitor fluid and electrolyte balance closely. Ensure adequate hydration. Infuse intravenously into large veins to prevent extravasation.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Urea?
A: See Dosage section for details as it depends on indication, patient’s age, weight and condition.
Q2: How is urea administered?
A: Urea can be administered intravenously, orally, or topically depending on the indication.
Q3: What are the primary uses of urea in medical practice?
A: Primarily used to reduce intracranial or intraocular pressure and as an osmotic diuretic. It also serves as a medical food for the management of hyponatremia and in topical treatment of certain skin conditions.
Q4: What are the key monitoring parameters during urea therapy?
A: Monitor serum sodium, blood urea nitrogen (BUN), creatinine, urine output, and vital signs.
Q5: Are there specific dosage adjustments for patients with renal or hepatic impairment?
A: Yes, dosage adjustments are usually necessary for patients with renal or hepatic impairment. Urea is contraindicated in severe renal dysfunction. Exercise caution in hepatic impairment.
Q6: Can urea be used during pregnancy and breastfeeding?
A: Use with caution during pregnancy only if clearly needed. Limited data available regarding safety during breastfeeding.
Q7: What are the common side effects of urea?
A: Common side effects include headache, nausea, vomiting, and dehydration.
Q8: Are there any serious adverse reactions associated with urea?
A: Yes, although rare, serious adverse reactions include syncope, bradycardia, and extravasation leading to tissue necrosis.
Q9: What are the contraindications to using urea?
A: Contraindications include severe renal impairment, marked dehydration, active intracranial bleeding, and liver failure.
