Ammonium bromide

Dermal absorption

Administrative data

Endpoint:

dermal absorption in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1985

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: No guideline available for this type of special investigation.

Data source

Reference

Reference Type:

publication

Title:

Skin Penetration of minerals in Psoriatics and Guinea-Pigs Bathing in Hypertonic Salt Solutions

Author:

Shani, J. et al

Year:

1985

Bibliographic source:

Pharmacological Research Communications, Vol. 17, No. 6

Materials and methods

Test guideline

Qualifier:

no guideline available

Guideline:

other: no guideline available for this type of special investigation

Principles of method if other than guideline:

Study was performed according to good experimental practice.

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

Hypertonic salt solution (dead sea bath salt)

IUPAC Name:

Hypertonic salt solution (dead sea bath salt)

Details on test material:

- Name of test material (as cited in study report): Hypertonic salt solution (dead sea bath salt)
- Radiolabelling: performed for the experiments in guinea-pigs only (47Ca, 28Mg, 42K and 82Br)
- Specific activity of test substance: The radiolabelled dead sea bath used for the guinea-pigs had an activity of 10 µCi/L of each radionuclide.
- No further details given on test substance within the publication.
Ammonium bromide is an inorganic salt that dissociates to its composite ions in aqueous solutions at environmental pH and temperature. Comparison of the available data on the various bromide salts have shown that the bromide ion is the relevant ion for determination of the toxicological profile with simple cations such as potassium, sodium or ammonium, that are ubiquitous in nature, having little or no influence on the bromide ion properties. It is therefore justified to read-across data from other inorganic bromide salts to ammonium bromide.

Radiolabelling:

yes

Remarks:

47Ca, 28Mg, 42K and 82Br (guinea pigs only)

Test animals

Species:

other: Human (healthy Israeli volunteers, psoriatic Danes), Guinea-pig

Strain:

other: Guinea-pig: Sabra Albino; humans: not indicated

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Not applicable
- Age at study initiation: The Israeli were between 20 and 48, and the Danes between 16 and 69 years of age. The Age of te guinea pigs is not stated within the publication.
- Weight at study initiation: Guinea-pigs were within a weight range of 250-300 g. Weight of the human volunteers is not stated within the publication.

Administration / exposure

Type of coverage:

other: no coverage; exposure towards test material via bathing.

Vehicle:

water

Duration of exposure:

humans: 30 minutes/bath
guinea-pigs: 60 minutes/bath

Doses:

1.5, 5 or 15% of hypertonic salt solution (dead sea bath salt) corresponding to a concentration of 0.0096, 0.032 and 0.096% of bromide, respectively.

It has been reported that the dead sea contains 300-320 g/L salts, of which KCl, MgCl2, CaCl2 and NaCl represent the major proportion (98% of the dried salt). The other 2% consist of bromide salts, heavy metals, trace elements and solids. Thus, the concentration of bromide in the “pure” dead sea is 2% or 6-6.4 g/L at maximum. Consequently, a 1.5, 5 or 15% dead sea bath salt solution contains 4.8, 16 and 48 g/L of total salts or 0.096, 0.32 and 0.96 g/L of bromide at maximum (corresponding to a concentration of 0.0096, 0.032 and 0.096% of bromide, respectively).

No. of animals per group:

6 healthy human volunteers per group
21 psoriatic patients in total
9-12 guinea-pigs per group

Control animals:

no

Details on study design:

APPLICATION OF DOSE:

VEHICLE
- Concentration (if solution): 1.5, 5 or 15% of hypertonic salt solution (dead sea bath salt) corresponding to a concentration of 0.0096, 0.032 and 0.096% of bromide, respectively

TEST SITE
- Preparation of test site: Guinea-pigs were shaven.
- Area of exposure: Whole body exposure
- % coverage: approximately 100 %

SAMPLE COLLECTION
- Samples from humans were taken before and directly after exposure/bathing and 4 weeks after study initiation for the psoriatic patients.
-Guinea-pig samples were taken directly after bathing.
- Samples taken: Blood (humans); blood, liver, spleen, lungs, heart, brain, stomach, small intestine, skin, bone, kidney, uteri, ovaries, testes, placenta, foetus and milk from lactating mothers (guinea-pigs)

Results and discussion

Signs and symptoms of toxicity:

no effects

Dermal irritation:

no effects

Absorption in different matrices:

Elemental analysis of human serum revealed significant penetration of four ions through the psoriatic skin, and penetration of only one ion (calcium) through the healthy skin, after bathing in the Dead Sea for one month, 30 minutes each. No increase in the levels of any of the ions measured was detected in the healthy volunteers after their 30-minutes bathing in the simulated bath salt solutions. The ions elevated in the sera of the psoriatic patients after one month of daily bathing in the Dead Sea were Br, Rb, Ca and Zn. Even though the serum was concentrated before its analysis, and the detection limits were low (0.06-4 µg/L), only 9 elements could be analyzed by X-ray fluorescence and 4 by atomic absorption. Further lowering of these detection limits by a factor of 10 could not have made it possible to determine more elements.
Analysis of penetration of radionuclides through the guinea-pig skin demonstrate that the same radionuclide accumulate in the same internal organs in all four groups studied (pregnant, lactating and cycling females as well as mature males). Of high significance were the following elemental retentions: 47Ca concentrated over 270-fold in the skin and significantly also in the bone, spleen, milk and ovaries; 28Mg concentrated in the skin, ovaries, spleen, heart and bone; 42K was absorbed in the skin, and found its way to the bone, ovaries, spleen and amniotic fluid, while 82Br concentrated in the skin, testes and bone, but not in the spleen. Some sporadic uptake was noticed for some of the radionuclides in other organs, i.e. 42K in uteri of cycling animals and 82Br in pregnant guinea-pigs ovaries. Organ-to-blood-ratios below 3 were not considered meaningful. In some cases a certain radionuclide concentrated differently in the same organ excised from different animal groups.

Applicant's summary and conclusion

Conclusions:

It seems reasonable to conclude that psoriatic skin is more penetrable to most elements than healthy skin, and that some penetration may occur even if diluted Dead Sea water is used. Most importantly, analysis of human serum revealed significant penetration of four ions through the psoriatic skin, and penetration of only one ion (calcium) through the healthy skin, after bathing in the Dead Sea for one month, 30 minutes each. No increase in the levels of any of the ions measured was detected in the healthy volunteers after their 30-minutes bathing in the simulated bath salt solutions. In general, the absolute penetration values after bathing in the Dead Sea brine are low through human skin. In addition, the differences between the human and animal skin is paralleled by the differences in their electrical conductance, but the differences in permeability between the various ions in the same species is not significant. The results of this investigation also demonstrated no absorption of the bromide ion through intact skin of humans.

Executive summary:

Materials and Methods

Penetration of minerals from radiolabelled hypertonic salt solutions into the human circulation was investigated, since medical effects are supposed after bathing in the Dead Sea. The study was undertaken to find out whether and to what extent minerals are capable of penetrating the skin from a hypertonic solution as occurs in the Dead Sea. Penetration of electrolytes through the human skin was measured in healthy volunteers and in psoriatic patients after bathing in the dead sea or in simulated bath salt solutions. Levels of Br, Sr, Rb, Se, Fe, Ca, K, Zn, Cu, Na, Mg, Cr and Cl were determined in serum. In addition, guinea-pigs were bathed in a simulated dead sea bath salt solution containing radionuclides of calcium, magnesium, potassium and bromide. Blood, liver, spleen, lungs, heart, brain, stomach, small intestine, skin, bone, kidney, uteri, ovaries, testes, placenta, foetus and milk from lactating mothers were observed for these ions after 60 minutes of bathing.

Results and Discussion

The dead sea contains 300-320 g/L salts, of which KCl, MgCl2, CaCl2 and NaCl are the major ones (98% of the dried salt). The other 2% consist of bromide salts, heavy metals, trace elements and solids. Psoriasis is a complex proliferative skin disease, showing partially uncontrolled non-malignant growth of the epidermis. Its aetiology is unknown, but is apparently related to imbalanced cyclic nucleotides. In such a case a treatment for psoriasis should to a large extent be via the circulation, supplying some elemental ions for cAMP production. This aspect has been studied for sodium, potassium, copper, selenium and bromine. Moreover, psoriasis has been treated successfully by salt combinations both externally and internally, and it was suggested that a possible mechanism of the latter treatment (sodium bromide administration) is partially via the known sedative effect of bromide on stress-induced psoriasis. Assuming that the therapeutic effect of the Dead Sea is in part due to its mineral content, clinical effectiveness studies of bathing in it were focused on the ability of its various minerals to penetrate through or into the epidermis. This is a slow process as the intact stratum corneum is limiting percutaneous absorption and minerals are extremely insoluble in lipid membranes and their transport via the intracellular route is limited. The questions raised in this study are whether one can expect measurable penetration of minerals through the skin after only a short (30-60 minutes) bathing in a salt solution; and is there any difference in penetration between psoriatic and healthy human skin. There are varying views regarding the lag-time needed for ionic species to penetrate into the circulation. According to one publication, 24Na, 82Br and 32P begin to penetrate the skin within 10 minutes of their application and dynamic equilibrium is reached by 50 minutes. The present study in guinea-pigs demonstrates that after 60 minutes of bathing the whole body in the salt solution, and having a sensitive measurement system (radioisotypic counting), the concentration of the various elements in blood and body tissues could be measured with high accuracy and reliability. Besides, it could be demonstrated that penetration of dead sea minerals via psoriatic skin is more profound than through a healthy skin. It is well established from clinical experience that absorption is increased through damaged skin, and that a skin injury comparable to eczema is most simply induced experimentally by tripping. The authors of the investigation postulate that in the psoriatic skin, with its abnormal capillary dilatation and damaged stratum corneum, penetration rates are higher because of the partial lack of protection of the damaged stratum corneum. An additional factor which enhances minerals penetration into the psoriatic skin is the frequent use by the patients of a keratolytic ointment (i.e. 3-5% salicylic acid) and vaselin. The latter base is known to increase the permeability of the stratum corneum 4-5 fold, as it can then take 4-times its weight of water. Permeability of the skin in different mammalian species varies remarkably. The differences between the human and animal skin is paralleled by the differences in their electrical conductance, but the differences in permeability between the various ions in the same species is not significant. If any generalisation is at all possible, it would seem that human skin is more impermeable than the skin of a guinea-pig, and that guinea pig skin may in some cases serve as useful approximation to human skin testing its permeability. At worse, the penetration of dead sea minerals through guinea-pig skin will be an overestimation of what is occurring under similar conditions in the human. In a series of papers it had been demonstrated that the maximum penetration of the ions through skin was observed when the solute had low salt rather than high salt, and that the more concentrated the external solution is, the less penetrable through the skin are the ions soluble in it. Significantly less 131I penetrated the skin from a 30% NaCl solution than from 3% or 1% NaCl solutions, but the amount which penetrated was still measurable in all three concentrations. Similar experiments were carried out by another research group. Inasmuch as ions do penetrate the human skin, their absolute penetration values after bathing in the Dead Sea brine are low (please refer to Table A6.2/06-1). In a previous paper the authors described higher concentration of bromine skin of Dead Sea workers and in psoriatic patients after a longer stay on the Dead Sea shore. It is suggested that this element also enters the body through breathing and drinking.