Products
In many countries, urea ointment 40% is sold as a medical product (Onyster). A urea ointment can also be prepared in a pharmacy, for example as an extemporaneous formulation (see below). Bayer discontinued the sale of the Canesten nail set in 2016. In Germany and Austria, the urea ointment also contains the azole antifungal agent bifonazole as a fixed combination (D: Canesten Extra Nagelset).
Structure and properties
Urea or carbamide (CH4N2O, Mr = 60.1 g/mol) exists as a white crystalline powder or as transparent crystals and is very soluble in water. Urea is a natural substance that also occurs in the human body.
Production
A urea ointment 40% can be prepared by simple means (according to NRF 11.30):
| A | Urea | 40.0 g |
| B | White vaseline | 40.0 g |
| C | Lanolin | 20.0 g |
B and C are mixed and blended with A to form a paste, which may have a granular appearance. Shelf life: 6 months (pot) or 1 year (tube). Alternative manufacturing instructions exist. It should be noted that urea can decompose in acidic and alkaline environments.
Effects
Urea (ATC D02AE01) has keratolytic properties by altering the structure and properties of the keratin of the nails. This leads to softening of the diseased parts of the nail. As a result, they can be easily removed.
Fields of application
For local treatment of a nail fungus of the finger or toe nails. In sequential combination with an antifungal agent.
Dosage
According to the package insert. The ointment is applied thinly to the affected nail once daily and occlusively taped with a special plaster.
- The urea ointment should not get on the skin. Avoid contact with the eyes and mucous membranes.
- Wash hands well after administration or apply directly from the tube, with gloves or an applicator.
- After 24 hours, the patch is removed. The nail is softened with a foot bath for 10 minutes and dried. Subsequently, the diseased nail substance is removed superficially with the spatula.
- This procedure is repeated during two to three weeks until the diseased part of the nail is removed.
Now the treatment is continued with an antifungal cream:
- Switzerland: clotrimazole cream, morning and evening for 5-6 weeks.
- Germany/Austria: Bifonazole cream, once daily during 4 weeks.
Contraindications
Treatment is contraindicated in case of hypersensitivity. Avoid contact with the eyes or mucous membranes. Do not ingest ointment. For complete precautions, see the Instructions for Use.
Interactions
There are no known drug-drug interactions.
Adverse effects
Possible adverse effects include local reactions such as inflammation and softening of the skin, hypersensitivity reactions, rash, itching, and pain at the site of administration. The nail may become discolored or grow incorrectly.
