Allantoin

Dermal absorption

Administrative data

Endpoint:

dermal absorption in vivo

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: Non-standard study using only 6 test subjects.

Data source

Reference

Reference Type:

publication

Title:

The effect of vehicle on allantoin penetration into human skin from an ointment for improving scar elasticity

Author:

Sznitowska, M. and S. Janicki

Year:

1988

Bibliographic source:

Pharmazie 43 (1988), H.3

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

Skin penetration of allantoin in three ointment bases was determined in 6 human subjects (male and female).

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

Allantoin

EC Number:

202-592-8

EC Name:

Allantoin

Cas Number:

97-59-6

Molecular formula:

C4H6N4O3

IUPAC Name:

1-(2,5-dioxoimidazolidin-4-yl)urea

Details on test material:

- Name of test material (as cited in study report): Allantoin
- Substance type: active substance
- Physical state: emulsion
- Analytical purity: no data
- Impurities (identity and concentrations): no data
- Composition of test material, percentage of components: All ointments consisted of the same quantity of the active ingredients: heparin 5000 I.U. (Polfa), allantoin 1.0 (Carl Roth KG), a liquid extract of onion bulb 20.0, Azulan, an ethanolic extract of Anthodium Chamomillae 5.0 (Herbapol) in 100.0 g of the ointment
- Isomers composition: not applicable
- Purity test date: no data
- Lot/batch No.: no data
- Expiration date of the lot/batch: no data
- Stability under test conditions: no data
- Storage condition of test material: no data
- Other: A 5% w/w aqueous solution of methyl cellulose with added glycerol and propylene glycol was the basis of the hydrophilic gel. A mixture of emulsifying agents: sodium lauryl sulphate and cetostearyl alcohol was used to obtain the O/W ointment. The W/O emulsion base contained cetyl alcohol and cholesterol.

Radiolabelling:

no

Test animals

Species:

human

Strain:

other: not applicable

Sex:

male/female

Details on test animals or test system and environmental conditions:

The experiment was carried out on 6 individuals (women and men).

Administration / exposure

Type of coverage:

occlusive

Vehicle:

other: Three different ointment matrices: a hydrophilic gel, a O/W ointment and a W/O emulsion.

Duration of exposure:

3 hours and 6 hours

Doses:

- Nominal doses: 0.5 g of ointment - all ointments consisted of the same quantity of the active ingredients: heparin 5000 I.U., allantoin 1.0, a liquid extract of onion bulb 20.0, Azulan, an ethanolic extract of Anthodium Chamomillae 5.0 in 100.0 g of the ointment.
- Actual doses: no data
- Actual doses calculated as follows: not applicable
- Dose volume: no data
- Rationale for dose selection: not applicable

No. of animals per group:

6 (male and female)

Control animals:

no

Details on study design:

DOSE PREPARATION
- Method for preparation of dose suspensions: all ointments consisted of the same quantity of the active ingredients: heparin 5000 I.U., allantoin 1.0, a liquid extract of onion bulb 20.0, Azulan, an ethanolic extract of Anthodium Chamomillae 5.0 in 100.0 g of the ointment.
- Method of storage: no data

APPLICATION OF DOSE:

VEHICLE
- Justification for use and choice of vehicle (if other than water): This experiment attempts to determine the effect of the physicochemical form of the base (i.e., ointment) on the allantoin bioavailability.
- Amount(s) applied (volume or weight with unit): 0.5 g ointment
- Concentration (if solution): A 5% w/w aqueous solution of methyl cellulose with added glycerol and propylene glycol was the basis of the hydrophilic gel. A mixture of emulsifying agents: sodium lauryl sulphate and cetostearyl alcohol was used to obtain the O/W ointment. The W/O emulsion base contained cetyl alcohol and cholesterol.
- Lot/batch no. (if required): no data
- Purity: no data

TEST SITE
- Preparation of test site: Plastic plates were used to apply the ointment samples to the skin.
- Area of exposure: Each plate had an indentation measuring 20 x 50 x 1 mm where a sample of 0.5 g of the ointment was put. The plate with the ointment was placed on the skin of the inner forearm.
- % coverage: no data
- Type of cover / wrap if used: The plate was covered with an adhesive dressing.
- Time intervals for shavings or clippings: not applicable

SITE PROTECTION / USE OF RESTRAINERS FOR PREVENTING INGESTION: no

REMOVAL OF TEST SUBSTANCE
- Removal of protecting device: After 3 hr one plate was removed and the other after 6 hr for each test subject.
- Washing procedures and type of cleansing agent: The ointment was carefully collected from the skin and the plate using a spatula and cotton wool moistened with ethanol.
- Time after start of exposure: 3 hr and 6 hr.

SAMPLE COLLECTION
- Collection of blood: not applicable
- Collection of urine and faeces: not applicable
- Collection of expired air: not applicable
- Terminal procedure: not applicable
- Analysis of organs: not applicable

SAMPLE PREPARATION
- Storage procedure: no data
- Preparation details: The collected ointments, together with the cotton wool, were transferred to a 100 cm3 conical flask. The extraction of allantoin from the bases was carried out, according to the ointment formulation, in one of the following ways:
-- The gel was shaken with 50.0 cm3 of distilled water at 50 deg C for 1 hr. Then the solution was filtered. 10.0 cm3 of the filtrate was made up with distilled water to 50.0 cm3.
-- The O/W ointment was shaken with 50.0 cm3 of distilled water at 50 deg C for 40 min. The resulting emulsion was cooled to 4 deg C and centrifuged (3,000 r.p.m.). 10.0 cm3 of the water phase was made up with distilled water to 50.0 cm3.
-- The W/O ointment was shaken with approximately 30 cm3 of distilled water at 60 deg C for 15 min. After cooling the water phase was filtered and the extraction procedure was repeated twice. The collected filtrates were made up of 250.0 cm3 with distilled water.

ANALYSIS
- Method type(s) for identification: The allantoin concentration in the extracts was determined employing the spectrophotometric method in UV region.
- Liquid scintillation counting results (cpm) converted to dpm as follows: not applicable
- Validation of analytical procedure: no data
- Limits of detection and quantification: no data

OTHER: To evaluate the loss of allantoin when it was removed from the skin the ointments were applied to the skin as already described and were removed after 5 min. The procedure was repeated 5 times for each ointment formulation. The allantoin content in the collected samples was determined in the same way as for the other samples.

Details on in vitro test system (if applicable):

Not applicable

Results and discussion

Signs and symptoms of toxicity:

not examined

Dermal irritation:

not examined

Absorption in different matrices:

Not examined.

Total recovery:

Not examined.

Percutaneous absorption

Percutaneous absorption 1

Dose:

0.5 g ointment

Parameter:

percentage

Absorption:

ca. 5 %

Remarks on result:

other: 3 hr

Remarks:

Allantoin in Hydrophilic gel

Percutaneous absorption 2

Dose:

0.5 g ointment

Parameter:

percentage

Absorption:

ca. 6.9 %

Remarks on result:

other: 6 hr

Remarks:

Allantoin in Hydrophilic gel

Percutaneous absorption 3

Dose:

0.5 g ointment

Parameter:

percentage

Absorption:

ca. 13 %

Remarks on result:

other: 3 hr

Remarks:

Allantoin in O/W cream

Percutaneous absorption 4

Dose:

0.5 g ointment

Parameter:

percentage

Absorption:

ca. 15.4 %

Remarks on result:

other: 6 hr

Remarks:

Allantoin in O/W cream

Percutaneous absorption 5

Dose:

0.5 g ointment

Parameter:

percentage

Absorption:

ca. 12.5 %

Remarks on result:

other: 3 hr

Remarks:

Allantoin in W/O ointment

Percutaneous absorption 6

Dose:

0.5 g ointment

Parameter:

percentage

Absorption:

ca. 20 %

Remarks on result:

other: 6 hr

Remarks:

Allantoin in W/O ointment

Conversion factor human vs. animal skin:

Not applicable

Any other information on results incl. tables

In the following table the amounts of allantoin which penetrated the skin after 3 and 6 hr of ointment application are presented as a percentage of the total initial dose. The values given are the means of determinations on 6 individuals.

The influence of vehicle on the amount of allantoin diffusing from the ointment into the human skin after 3 hr and 6 hr:

Type of Vehicle	Percentage of allantoin diffusing into the skin after the investigated time
	3 hr.			6 hr.
	Mean	S.D.	n	Mean	S.D.	n
Hydrophilic gel	5.0	1.25	6	6.9	1.4	6
O/W cream	13.0	1.8	6	15.4	2.7	6
W/O ointment	12.5	2.1	6	20.0	2.3	6

It was ascertained experimentally that the ointment was removed from the skin with sufficient accuracy. The allantoin remaining in the ointments after an application of 5 min. duration was determined to be as follows: gel 100.5%, W/O ointment 99.7%, O/W cream 98.8%.

Applicant's summary and conclusion

Conclusions:

Depending on the ointment vehicle used, the diffusion rate of allantoin into the skin of 6 human subjects following a 3 hour exposure ranged from 5% to 13% of the initial dose. Following a 6 hour exposure, the diffusion rate ranged from 6.9% to 20% of the initial dose.