S-Caine (lidocaine and tetracaine) 7%/7% cream is a topical local anesthetic cream that forms a pliable peel on the skin when exposed to air. The drug formulation is an emulsion in which the oil phase is a 1:1 eutectic mixture of lidocaine 7% and tetracaine 7%. The eutectic mixture has a melting point below room temperature and therefore both local anesthetics exist as a liquid oil rather than as crystals. The net weight of lidocaine is 2.1 g and of tetracaine is 2.1 g per tube.

Lidocaine is chemically designated as acetamide, 2-(diethylamino)-N-(2,6-dimethylphenyl) and has an octanol:water partition ratio of 182 at pH 7.3. The molecular weight of lidocaine is 234.3, and the molecular formula is C₁₄H₂₂N₂O. The structural formula is:

Tetracaine is chemically designated as 2-dimethylaminoethyl 4-n-butylaminobenzoate and has an octanol:water partition ratio of 5370 at pH 7.3. The molecular weight of tetracaine is 264.4, and the molecular formula is C₁₅H₂₄N₂O₂. The structural formula is:

Each gram of S-Caine contains lidocaine 70 mg and tetracaine 70 mg in a 1:1 eutectic mixture and it also contains the following inactive ingredients: dibasic calcium phosphate, methylparaben, petrolatum, polyvinyl alcohol, propylparaben, sorbitan monopalmitate and water.

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