Lactic Acid
Indications: Ichthyosis vulgaris; Xerosis
DESCRIPTION:
Lac-Hydrin 12% Cream: For dermatologic use only. Not for ophthalmic, oral or intravaginal use.
Lac-Hydrin is a formulation of 12% lactic acid neutralized with ammonium hydroxide, as ammonium lactate, with a pH of 4.4 to 5.4. Lac-Hydrin cream also contains water, light mineral oil, glyceryl stearate, polyoxyl 100 stearate, propylene glycol, polyoxyl 40 stearate, glycerin, cetyl alcohol, magnesium aluminum silicate, laureth-4, methyl and propyl parabens, methylcellulose, and quaternium-15. Lactic acid is a racemic mixture of 2-hydroxypropanoic acid.
Lac-Hydrin 12% Lotion: For topical use only. Not for ophthalmic use.
Lac-Hydrin, specially formulates 12% lactic acid neutralized with ammonium hydroxide, as ammonium lactate to provide a lotion pH of 4.5 to 5.5. Lac-Hydrin also contains light mineral oil, glyceryl stearate, PEG-100 stearate, propylene glycol, polyoxyl 40 stearate, glycerin, magnesium aluminum silicate, laureth-4, cetyl alcohol, methyl and propylparabens, methylcellulose, fragrance, quaternium-15 and water. Lactic acid is a racemic mixture of 2-hydroxypropanoic acid.
CLINICAL PHARMACOLOGY:
Cream
Lactic acid is an alpha-hydroxy acid. It is a normal constituent of tissues and blood. The alpha-hydroxy acids (and their salts) are felt to act as humectants when applied to the skin. This property may influence hydration of the stratum corneum. In addition, lactic acid, when applied to the skin, may act to decrease corneocyte cohesion. The mechanism(s) by which this is accomplished is not yet known.
An in vitro study of percutaneous absorption of lactic acid cream using human cadaver skin indicates that approximately 6.1% of the material was absorbed after 68 hours.
Lotion
It is generally accepted that the water content of the stratum corneum is a controlling factor in maintaining skin flexibility. When the stratum corneum contains more than 10% water it remains soft and pliable; however, when the water content drops below 10% the stratum corneum becomes less flexible and rough, and may exhibit scaling and cracking and the underlying skin may become irritated.1,2
Symptomatic relief of dry skin is provided by skin protectants containing hygroscopic substances (humectants) which increase skin moisture. Lactic acid, an alpha-hydroxy acid, is reported to be one of the most effective naturally occurring humectants in the skin.3 The alpha-hydroxy acids (and their salts), in addition to having beneficial effects on dry skin, have also been shown to reduce excessive epidermal keratinization in patients with hyperkeratotic conditions (e.g., ichthyosis).4
Pharmacokinetics: The mechanism of action of topically applied neutralized lactic acid is not yet known.
INDICATIONS AND USAGE:
Cream: Lactic acid cream is indicated for the treatment of ichthyosis vulgaris and xerosis.
Lotion: Lactic acid lotion is indicated for the treatment of dry, scaly skin (xerosis) and ichthyosis vulgaris and for temporary relief of itching associated with these conditions.
CONTRAINDICATIONS:
Cream: None known.
Lotion: Known hypersensitivity to any of the label ingredients.
WARNINGS:
Cream: Use of this product should be discontinued if hypersensitivity to any of the ingredients is noted. Sun exposure (natural or artificial sunlight) to areas of the skin treated with lactic acid cream should be minimized or avoided (see PRECAUTIONS).
PRECAUTIONS:
General
Cream: For external use only. Stinging or burning may occur when applied to skin with fissures, erosions, or that is otherwise abraded (for example, after shaving the legs). Caution is advised when used on the face because of the potential for irritation. The potential for post-inflammatory hypo- or hyperpigmentation has not been studied.
Lotion: For external use only. Avoid contact with eyes, lips or mucous membranes. Caution is advised when used on the face of fair-skinned individuals since irritation may occur. A mild, transient stinging may occur on application to abraded or inflamed areas or in individuals with sensitive skin.
Information for the Patient
Cream
Patients using lactic acid cream should receive the following information and instructions:
1. This medication is to be used as directed by the physician, and should not be used for any disorder other than for which it was prescribed. Caution is advised when used on the face because of the potential for irritation. It is for external use only. Avoid contact with eyes, lips, or mucous membranes.
2. Patients should minimize or avoid use of this product on areas of the skin that may be exposed to natural or artificial sunlight, including the face. If sun exposure is unavoidable, clothing should be worn to protect the skin.
3. This medication may cause stinging or burning when applied to skin with fissures, erosions, or abrasions (for example, after shaving the legs).
4. If the skin condition worsens with treatment, the medication should be promptly discontinued.
Carcinogenesis, Mutagenesis, and Impairment of Fertility
Cream
Carcinogenesis: A long-term photocarcinogenicity study in hairless albino mice suggested that topically applied 12% ammonium lactate cream enhanced the rate of ultraviolet light-induced skin tumor formation. Although the biologic significance of these results to humans is not clear, patients should minimize or avoid use of this product on areas of the skin that may be exposed to natural or artificial sunlight, including the face. Long-term dermal carcinogenicity studies in animals have not been conducted to evaluate the carcinogenic potential of ammonium lactate.
Lotion
Lactic acid lotion was non-mutagenic in the Ames/Salmonella/Microsome Plate Assay. Reproductive studies in rats given lactic acid orally showed no effect on the sex ratio of the offspring.5
Pregnancy, Teratogenic Effects, Pregnancy Category C
Animal reproduction studies have not been conducted with lactic acid. It is also not known whether lactic acid can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity. Lactic acid should be given to a pregnant woman only if clearly needed.
Nursing Mothers
Although lactic acid is a normal constituent of blood and tissues, it is not known to what extent this drug affects normal lactic acid levels in human milk. Because many drugs are excreted in human milk, caution should be exercised when lactic acid is administered to a nursing woman.
Pediatric Use
Cream: The safety and effectiveness of lactic acid cream have not been established in pediatric patients less than 12 years old. Potential systemic toxicity from percutaneous absorption has not been studied. Because of the increased surface area to body weight ratio in pediatric patients, the systemic burden of lactic acid may be increased.
Lotion: Safety and effectiveness of lactic acid lotion have been demonstrated in infants and children. No unusual toxic effects were reported.
ADVERSE REACTIONS:
Cream
In controlled clinical trials of patients with ichthyosis vulgaris, the most frequent adverse reactions in patients treated with lactic acid cream were rash (including erythema and irritation) and burning/stinging. Each was reported in approximately 10% to 15% of patients. In addition, itching was reported in approximately 5% of patients.
In controlled clinical trials of patients with xerosis, the most frequent adverse reactions in patients treated with lactic acid cream were transient burning, in about 3% of patients, stinging, dry skin and rash, each reported in approximately 2% of patients.
Lotion
The most frequent adverse experiences in patients with xerosis are transient stinging (1 in 30 patients), burning (1 in 30 patients), erythema (1 in 50 patients) and peeling (1 in 60 patients). Other adverse reactions which occur less frequently are irritation, eczema, petechiae, dryness and hyperpigmentation.
Due to the more severe initial skin conditions associated with ichthyosis, there was a higher incidence of transient stinging, burning and erythema (each occurring in 1 in 10 patients).
OVERDOSAGE:
Lotion: The oral administration of lactic acid to rats and mice showed this drug to be practically non-toxic (LD50 >15 ml/kg).
DOSAGE AND ADMINISTRATION:
Cream: Apply to the affected areas and rub in thoroughly. Use twice daily or as directed by a physician.
Lotion: Shake well. Apply to the affected areas and rub in thoroughly. Use twice daily or as directed by a physician.
REFERENCES:
1. Blank IH: Further observation on factors which influence the water content of the stratum corneum. J Invest Dermatol 21: 259-271, 1953.
2. Blank IH: Factors which influence the water content of the stratum corneum. J Invest Dermatol 18: 433-440, 1952.
3. Middleton JD: Sodium lactate as a moisturizer. Cosmetics and Toiletries 93: 85-86, 1978.
4. VanScott EJ and Yu RJ: Modulations of keratinization with alpha-hydroxy acids and related compounds. In: Recent Advances in Dermatopharmacology, P. Frost, E.E. Gomez and N. Zaias (eds) Spectrum Publications, Inc. NY, 211-217, 1977.
5. D'Amour FE: Effects of feeding Sodium bicarbonate or lactic acid upon the sex ratio in rats. Science 79: 61-62, 1934.