AHA, PHA, and Bionic Acid Use in Dermatology

AHAs are used extensively as adjunctive agents in the treatment of hyperkeratotic disorders including psoriasis, callouses, acne, keratosis pilaris, and keratoses (6,8,27). They are considered among the best therapeutic options for the treatment of most forms of ichthyosis (24,25). These compounds are also used ubiquitously for the treatment of aging-related skin changes. AHAs are marketed in a variety of forms that are readily available to physicians including superficial peel reagents, cleansers, creams, lotions, and gels.

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Figure 4 Lactobionic acid, a polyhydroxy bionic acid, is chemically defined as a bionic acid because it is comprised of two units: one gluconic acid molecule (right) and one galactose molecule (left).

Table 1 Chemical Exfoliants Exfoliation class Ingredient Regulatory status Solubility pKa Bioavailable (non – ionized) % at a selected formulation pH of 3.5а Common concen­tration range in topical formulations, % Alpha-hydroxy acid Glycolic acid Cosmetic Water-soluble 3.83 68% Up to 10% (AHA) Alpha-hydroxy acid (AHA) Lactic acid Cosmetic or Rx (12% ammonium lactate form) Water-soluble 3.86 70% Up to 10% Alpha – (and beta-) Citric acid Cosmetic Water-soluble 3.13 30% Up to 10% hydroxy acid (AHA) Alpha-hydroxy acid Mandelic acid Cosmetic Water-/alcohol-soluble 3.4 44% Up to 10% (AHA) Alpha-hydroxy acid (AHA) Benzilic acid Cosmetic Slightly soluble in water, freely soluble in alcohol, ether 3.0 24% Up to 10% Polyhydroxy acid (PHA) Gluconolactone/ gluconic acid Cosmetic Water-soluble 3.6 56% Up to 15% Bionic acid Lactobionic acid Cosmetic Water-soluble 3.8 68% Up to 15% Salicylic acid Salicylic acid OTC drug or cosmetic depending on claims Slightly soluble in water, freely soluble in alcohol, ether 2.97 23% 0.5-2.0% (OTC monograph) Acetyl amino sugars N-Acetylglucosamine Cosmetic Water-soluble Neutral N/A Up to 10% Calculation based on Henderson-Hasselbalch equation: pKa=pH + log [Acid]/[Base].

The PHAs and bionic acids are gaining use in dermatology due to their significant skin normalizing effects and anti-aging benefits in conjunction with their non-irritating characteristics. These non-irritating agents are especially useful on the sensitive skin of rosacea, atopic dermatitis, and post-procedure (microdermabrasion, peels, non-ablative laser, etc.) when the skin barrier has been disrupted and irritation or stinging is likely to occur due to the increased potential for rapid absorption of skin care ingredients (38,44).