STERILE UREA
Clinical safety rating: safe
Animal studies have demonstrated safety
Urea is a hygroscopic agent that increases the osmolarity of blood plasma, drawing water from tissues into the blood and enhancing urine output. It also acts as a topical keratolytic agent by dissolving intracellular matrix in the stratum corneum, promoting desquamation and softening hyperkeratotic skin.
| Metabolism | Urea is partially metabolized in the gastrointestinal tract by urease-producing bacteria, releasing ammonia. In the body, it is not significantly metabolized and is primarily excreted unchanged by the kidneys. |
| Excretion | Urea is primarily excreted renally, with approximately 90% eliminated unchanged in urine via glomerular filtration; negligible biliary or fecal elimination. |
| Half-life | Terminal elimination half-life is approximately 7-8 hours in patients with normal renal function; prolonged in renal impairment. |
| Protein binding | Negligible (<1%); does not significantly bind to plasma proteins. |
| Volume of Distribution | Vd approximately 0.5-0.7 L/kg, approximating total body water; distributes freely throughout extracellular and intracellular fluid. |
| Bioavailability | Oral: no systemic bioavailability as oral urea is degraded in gut; topical: negligible systemic absorption (<4% through intact skin). |
| Onset of Action | Intravenous: diuretic effect begins within 30-60 minutes; topical: keratolytic effect within minutes to hours. |
| Duration of Action | Diuretic effect lasts 3-6 hours post-IV; topical keratolytic effect lasts several hours depending on formulation. |
| Molecular Weight | 60.06 |
0.5-1.5 g/kg intravenously over 1-2 hours every 12-24 hours as needed for reduction of intracranial pressure. Oral: 40-60 g/day in divided doses as a diuretic.
| Dosage form | INJECTABLE |
| Renal impairment | Contraindicated in severe renal impairment (GFR <10 mL/min). For GFR 10-29 mL/min: reduce dose by 50% and monitor. No adjustment for GFR ≥30 mL/min. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B: reduce dose by 25%. Child-Pugh C: contraindicated due to risk of hyperammonemia. |
| Pediatric use | Intravenous: 0.5-1.5 g/kg/dose every 12-24 hours, not to exceed 120 g/day. Oral: 1-1.5 g/kg/day in divided doses for diuresis. |
| Geriatric use | Start at lower end of dosing range (0.5 g/kg IV), monitor renal function and fluid balance. Avoid in patients with dehydration or poor renal reserve. |
| 1st trimester | Urea is a normal constituent of blood and tissues. Exogenous urea administered intravenously or orally is not known to be teratogenic. However, there is insufficient data on use of intravenous urea in pregnant women. Use only if clearly needed. |
| 2nd trimester | Similar to T1. No known increase in congenital anomalies. Use if benefits outweigh risks. |
| 3rd trimester | Urea can cause osmotic diuresis and dehydration; monitor fluid balance. Avoid in preeclampsia or eclampsia due to risk of exacerbating hypertension or fluid shifts. |
Clinical note
No significant drug interactions For topical use only can cause mild irritation.
| Placental transfer | Urea crosses the placenta readily via simple diffusion. Placental transfer is rapid and complete, achieving equilibrium between maternal and fetal blood concentrations. |
| Breastfeeding | Urea is a normal component of breast milk. Exogenous urea is rapidly equilibrated and excreted into breast milk. No known adverse effects on infant. However, use caution in lactating women due to potential for osmotic effects if high doses are administered. |
■ FDA Black Box Warning
None
| Common Effects | xerosis |
| Serious Effects |
Anuria or severe oliguria (due to risk of fluid overload and azotemia)Intracranial bleeding (except during surgery)Severe dehydrationHypersensitivity to urea or any component of the formulation
| Precautions | Risk of fluid overload or electrolyte imbalance with prolonged use; monitor serum electrolytes and fluid status. Avoid extravasation when administering intravenously. Use with caution in patients with hepatic or renal impairment. Topical use may cause local irritation or burning sensation. |
| Food/Dietary | No significant food interactions for topical urea. Systemic urea is not used; if oral, avoid high-protein foods as they may increase BUN. |
Loading safety data…
| Lactation Rating | L1 (Safe) |
| Teratogenic Risk | Urea is considered to have low teratogenic risk. No human data indicate increased risk of major congenital malformations; however, use in the first trimester should be limited to situations where benefit clearly outweighs risk. In the third trimester, intravenous administration may cause maternal hypernatremia and fetal fluid shifts, which could theoretically affect fetal electrolyte balance. |
| Fetal Monitoring | Monitor maternal serum electrolytes (especially sodium), osmolality, and fluid status. Fetal monitoring for heart rate and fluid balance if high doses used. Assess for signs of maternal hypervolemia and hypertension. |
| Fertility Effects | No evidence of adverse effects on fertility in humans. In animal studies, no reproductive toxicity observed at therapeutic doses. |
| Clinical Pearls | Urea is used as a topical keratolytic for hyperkeratotic conditions. Systemic absorption is minimal, but prolonged use on large areas may lead to elevated BUN. Avoid contact with eyes and mucous membranes. Do not apply to infected or inflamed skin. |
| Patient Advice | Apply only to affected areas of skin as directed. · Avoid contact with eyes, mouth, and broken skin. · Do not use on deep wounds or infected skin. · Inform your doctor if irritation develops. · Keep out of reach of children. |