Abstract
The presence of impurities in medicinal products have to be controlled within safety limits from a pharmaceutical quality perspective. This matter is of special significance for those countries and regions where the directives, guidelines, or legislations, which prescribe the rules for the application of some products is quite selective or incomplete. Clay-based hydrogels are quite an example of this matter since they are topically administered, but, in some regions, they are not subjected to well-defined legal regulations. Since hydrogels establish an intimate contact with the skin, hazardous elements present in the ingredients could potentially be bioavailable and compromise their safety. The elemental composition and mobility of elements present in two hydrogels have been assessed. Sepiolite, palygorskite, and natural spring water were used as ingredients. The release of a particular element mainly depends on its position in the structure of the hydrogels, not only on its concentration in each ingredient. As a general trend, elements’ mobility reduced with time. Among the most dangerous elements, whose presence in cosmetics is strictly forbidden by European legal regulations, As and Cd were mobile, although in very low amounts (0.1 and 0.2 μg/100 g of hydrogel, respectively). That is, assuming 100% bioavailability, the studied hydrogels would be completely safe at normal doses. Although there is no sufficient evidence to confirm that their presence is detrimental to hydrogels safety, legally speaking, their mobility could hinder the authorization of these hydrogels as medicines or cosmetics. In conclusion, the present study demonstrates that hydrogels prepared with sepiolite, palygorskite, and Alicún spring water could be topically applied without major intoxication risks.
Highlights
The concentration and bioavailability of impurities such as hazardous elements in both health products and medicines is a main preformulation concern during their development
Elemental impurities in medicinal products have to be controlled within safety limits with different guidelines and normatives being useful from a pharmaceutical quality perspective
Nanoclay/natural spring water hydrogels have been prepared by mixing a sepiolite and a palygorskite with local spring water (Alicún de las Torres, Granada, Spain)
Summary
The concentration and bioavailability of impurities such as hazardous elements in both health products and medicines is a main preformulation concern during their development. Different health care products must comply with specific normatives and guidelines, depending on the administration route, and most of the times, on the region or country in which they are written and applied. In Canada, natural health products that do not require a medical prescription, are included in a guide in which heavy metals (Pb, As, Cd, Hg, and Sb, among others) are banned or limited to a maximum amount, in accordance with the administration route [1]. In the USA, similar health products fail into FDA legislation, which only considers Hg as a forbidden element and limits the Pb concentration [2]. European cosmetic legislation is much more detailed and restrictive regarding the presence of elemental impurities [3]
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