Generic Name: salicylic acid
Dosage Form: topical gel
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DESCRIPTION: Keralyt® is a gel for topical administration containing salicylic acid 6%, in a vehicle composed of propylene glycol, SD-40 alcohol (21%), hydroxypropylcellulose and purified water. Salicylic acid is the 2 hydroxy derivative of benzoic acid having the following structure:
CLINICAL PHARMACOLOGY: Salicylic acid has been shown to produce desquamation of the horny layer of skin while not affecting qualitative or quantitative changes in structure of the viable epidermis.¹, ² The mechanism of action has been attributed to a dissolution of intercellular cement substance.³ In a study of the percutaneous absorption of salicylic acid from Keralyt GEL in four patients with extensive active psoriasis, Taylor and Halprin⁴ showed that peak serum salicylate levels never exceeded 5 mg/100 ml even though more than 60% of the applied salicylic acid was absorbed. Systemic toxic reactions are usually associated with much higher serum levels (30 to 40 mg/100 ml). Peak serum levels occurred within 5 hours of the topical application under occlusion. The sites were occluded for 10 hours over the entire body surface below the neck. Since salicylates are distributed in the extracellular space, patients with a contracted extracellular space due to dehydration or diuretics have higher salicylate levels than those with a normal extracellular space.⁵ (See PRECAUTIONS).
The major metabolites identified in the urine after topical administration are salicyluric acid (52%), salicylate glucuronides (42%), and free salicylic acid (6%).³ The urinary metabolites after percutaneous absorption differ from those after oral salicylate administration; those derived from percutaneous absorption contain more glucuronides and less salicyluric and salicylic acid. Almost 95% of a single dose of salicylate is excreted within 24 hours of its entrance into the extracellular space.⁵
Fifty to eighty percent of salicylate is protein bound to albumin. Salicylates compete with the binding of several drugs and can modify the action of these drugs. By similar competitive mechanisms other drugs can influence the serum levels of salicylate.⁵ (See PRECAUTIONS).
INDICATIONS AND USAGE - For the removal of excess keratin in hyperkeratotic disorders, including scaling associated with scalp psoriasis or thickened skin of palms and soles, corns and calluses.
CONTRAINDICATIONS: Keralyt GEL should not be used in any patient known to be sensitive to salicylic acid or any other listed ingredient. Keralyt should not be used in children under 2 years of age.
WARNINGS: Prolonged use over large areas, especially in children and those patients with significant renal or hepatic impairment, could result in salicylism. Concomitant use of other drugs which may contribute to elevated serum salicylate levels should be avoided where the potential for toxicity is present. In children under 12 years of age and those patients with renal or hepatic impairment, the area to be treated should be limited and the patient monitored closely for signs of salicylate toxicity: nausea, vomiting, dizziness, loss of hearing, tinnitus, lethargy, hyperpnoea, diarrhea, psychic disturbances. In the event of salicylic acid toxicity, the use of Keralyt GEL should be discontinued. Fluids should be administered to promote urinary excretion. Treatment with sodium bicarbonate (oral or intravenous) should be instituted as appropriate.
Considering the potential risk of developing Reye’s Syndrome, salicylate products should not be administered to children or teenagers with varicella or influenza, unless directed by a physician.
PRECAUTIONS: For external use only. Avoid contact with eyes and other mucous membranes. Mild burning or stinging may occur. Peeling of the skin may increase as the salicylic acid works to loosen excess keratin. If excessive burning, stinging or peeling occurs, discontinue use and consult your physician. Flammable. Keep away from heat and open flame. Keep this and all medications out of reach of children.
Drug Interactions. (The following interactions are from a published review⁵ and include reports concerning both oral and topical salicylate administration. The relationship of these interactions to the use of Keralyt GEL is not known.)
I. Due to the competition of salicylate with other drugs for binding to serum albumin the following drug interactions may occur:
|Drug||Description of Interaction|
|Tolbutamide; Sulfonylureas||Hypoglycemia potentiated|
|Methotrexate||Decreases tubular reabsorption; clinical toxicity from methotrexate can result|
|Oral Anticoagulant||Increased bleeding|
II. Drugs changing salicylate levels by altering renal tubular reabsorption:
|Corticosteroids||Decreases plasma salicylate level; Tapering doses of steroids may promote salicylism|
|Ammonium Sulfate||Increases plasma salicylate level|
III. Drugs with complicated interactions with salicylates:
|Heparin||Salicylate decreases platelet adhesiveness and interferes with hemostasis in heparin-treated patients|
|Pyrazinamide||Inhibits pyrazinamide-induced hyperuricemia|
|Uricosuric Agents||Effect of probenecid, sulfinpyrazone and phenylbutazone inhibited|
The following alterations of laboratory tests have been reported during salicylate therapy⁶:
|Laboratory Tests||Effect of Salicylates|
|Thyroid Function||Decreased PBI; increased T3 uptake|
|Urinary Sugar||False negative with glucose oxidase; false positive with Clinitest with high-dose salicylate therapy (2-5 g qd)|
|5 Hydroxyindole acetic acid||False negative with fluorometric test|
|Acetone, Ketone Bodies||False positive FeCl3 in Gerhardt reaction; red color persists with boiling|
|17-OH corticosteroids||False reduced values with >4.8 g qd salicylate|
|Vanilmandelic Acid||False reduced values|
|Uric Acid||May increase or decrease depending on dose|
|Prothrombin||Decreased levels; slightly increased prothrombin time|
Pregnancy (Category C): Salicylic acid has been shown to be teratogenic in rats and monkeys. It is difficult to extrapolate from oral doses of acetyl salicylic acid used in these studies to topical administration as the oral dose to monkeys may represent 4 times the maximum daily human dose of salicylic acid (as supplied in one tube, 40 g of Keralyt GEL) when applied topically over a large body surface. There are no adequate and well-controlled studies in pregnant women. Keralyt GEL should be used during pregnancy only if the potential benefit justifies the risk to the fetus.
Nursing Mothers: Because of the potential for serious adverse reactions in nursing infants from the mother’s use of Keralyt GEL, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother.
ADVERSE REACTIONS: Excessive erythema and scaling conceivably could result from use on open skin lesions.
OVERDOSAGE - See WARNINGS
DOSAGE AND ADMINISTRATION - The preferable method of use is to apply Keralyt GEL thoroughly to the affected area and occlude the area at night. Preferably, the skin should be hydrated for at least five minutes prior to application. The medication is washed off in the morning and if excessive drying and/or irritation is observed a bland cream or lotion may be applied. Once clearing is apparent, the occasional use of Keralyt GEL will usually maintain the remission. In those areas where occlusion is difficult or impossible, application may be made more frequently; hydration by wet packs or baths prior to application apparently enhances the effect. Unless hands are being treated, hands should be rinsed thoroughly after application. For use as a scalp treatment: Keralyt GEL should be applied directly to the affected areas of the scalp on a frequency directed by your physician. The applicator tip will provide accurate application, avoiding contact with normal hair or skin. The gel should be washed off after 10 to 20 minutes initially, but it can be left on for up to an hour as treatment progresses. The gel can be washed off using Keralyt SHAMPOO or warm water in a bath or shower.
- Davies M, Marks R: Br J Dermatol 95: 187-192,1976.
- Marks R, Davies M, Cattel A: J Invest Dermatol 64: 283, 1975.
- Huber C, Christophers E: Arch Derm Res 257: 293-297, 1977.
- Taylor JR, Halprin KM: Arch Dermatol 111: 740-743, 1975.
- Goldsmith LA: Int J Dermatol 18: 32-36.
- Wilson JG, Ritter EJ, Scott WJ, Fradlein R: Tox Appl Pharmacol 41: 67-78, 1977.
EMS Contract Packaging, Hatfield, PA 19440
Summers Laboratories, Inc. Collegeville, PA 19426
1-800-533-SKIN (7546) • www.sumlab.com
Keralyt is a trademark of Summers Laboratories, Inc.
salicylic acid gel
|Labeler - Summers Laboratories Inc (002382612)|
|Summers Laboratories Inc||002382612||manufacture(11086-030), pack(11086-030)|