Lidocaine Patch 5%
DESCRIPTION
Lidocaine patch 5% is comprised of an adhesive material containing 5% lidocaine, which is applied to a non-woven polyester felt backing and covered with a polyethylene terephthalate (PET) film release liner. The release liner is removed prior to application to the skin. The size of the patch is 10 cm x 14 cm.Lidocaine is chemically designated as acetamide, 2-(diethylamino)-N-(2,6-dimethylphenyl), has an octanol:water partition ratio of 43 at pH 7.4, and has the following structure:
Each adhesive patch contains 700 mg of lidocaine (50 mg per gram adhesive) in an aqueous base. It also contains the following inactive ingredients: purified water, glycerin, sorbitol, polyacrylic acid, sodium carboxymethylcellulose, sodium polyacrylate, propylene glycol, urea, kaolin, tartaric acid, gelatin, polyvinyl alcohol, dihydroxyaluminum aminoacetate, edetate disodium, methylparaben, and propylparaben.
CLINICAL PHARMACOLOGY
Pharmacodynamics
Lidocaine is an amide-type local anesthetic agent and is suggested to stabilize neuronal membranes by inhibiting the ionic fluxes required for the initiation and conduction of impulses.
The penetration of lidocaine into intact skin after application of a lidocaine patch 5% is sufficient to produce an analgesic effect, but less than the amount necessary to produce a complete sensory block.
Pharmacokinetics
AbsorptionThe amount of lidocaine systemically absorbed from lidocaine patch 5% is directly related to both the duration of application and the surface area over which it is applied. In a pharmacokinetic study, three lidocaine patches were applied over an area of 420 cm2 of intact skin on the back of normal volunteers for 12 hours. Blood samples were withdrawn for determination of lidocaine concentration during the application and for 12 hours after removal of patches. The results are summarized in Table 1.
