Keralyt

KERALYT — salicylic acid gel
Physicians Total Care, Inc.

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KERALYT® is a gel for topical administration containing 6% salicylic acid 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:

Salicylic acid structureSalicylic acid 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 Halprin 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. (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.

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. (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

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.)

  1. Due to the competition of salicylate with other drugs for binding to serum albumin the following drug interactions may occur:
    DrugDescription of Interaction
    Tolbutamide; SulfonylureasHypoglycemia potentiated
    MethotrexateDecreases tubular reabsorption; clinical toxicity from methotrexate can result
    Oral AnticoagulantsIncreased bleeding
  2. Drugs changing salicylate levels by altering renal tubular reabsorption:
    DrugDescription
    CorticosteroidsDecreases plasma salicylate level;Tapering doses of steroids may promote salicylism
    Ammonium SulfateIncreases plasma salicylate level
  3. Drugs with complicated interactions with salicylates:
    DrugDescription
    HeparinSalicylate decreases platelet adhesiveness and interferes with hemostasis in heparin-treated patients
    PyrazinamideInhibits pyrazinamide-induced hyperuricemia
    Uricosuric AgentsEffect 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.

CARCINOGENESIS, MUTAGENESIS, IMPAIRMENT OF FERTILITY

No data are available concerning potential carcinogenic or reproductive effects of KERALYT GEL. It has been shown to lack mutagenic potential in the Ames Salmonella test.

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