Endo Pharmaceuticals Inc has released Synera (lidocaine 70 mg and tetracaine 70 mg), a topical anesthetic patch approved for use in patients aged 3 years and older (safety of Synera has been demonstrated in patients as young as 4 months old). Synera will be available in institutional settings to prevent pain from superficial venous access and superficial dermatologic procedures, such as excision, electrodessication, and shave biopsy.1
Although Synera is appropriate for use in both adult and pediatric populations, Endo Pharmaceuticals is especially aware of its need in hospitalized children. Patients less than 15 years old spend approximately 11.5 million days in the hospital. Endo Pharmaceuticals promotes Synera to prevent pain, thus increasing patient comfort and quality of care.1
Mechanism of Action
Synera consists of an oil emulsion of lidocaine and tetracaine as a eutectic mixture. The active ingredients cause local anesthesia by blockade of the sodium ion channels that are required for neuronal impulses and conduction.2
In addition to its active ingredients, Synera exhibits a warming component to augment the local anesthetic effect by enhancing its delivery. The heat generation and skin warming allow for the desirable effect of vasodilation. Upon removal from its packaging and exposure to oxygen, the patch begins to heat. Maximum skin temperature will not exceed 40º C.2
Several randomized, double-blind, placebo-controlled studies evaluated the efficacy of Synera in both children and adults. The first series of studies compared Synera with placebo prior to superficial venous access. The patch was applied 20 minutes prior to the needle stick. Results were measured with a 100- mm visual analog scale (VAS) and determined that there was less pain with Synera than with placebo.2
Additional clinical studies assessed the efficacy of Synera for superficial dermatologic procedures in adult and pediatric populations. In double-blind, randomized studies, Synera was applied 30 minutes before the procedure in both pediatric and adult patients. Synera was found more effective than placebo as assessed by VAS scores.2
The significance of Synera's heating component was evaluated in one double- blind, randomized trial. Prior to venipuncture, 250 adult patients received either Synera alone or Synera with heat. The group with the heating component reported less pain than the group without.2
For anesthesia prior to venipuncture or intravenous cannulation, Synera should be applied to the affected area 20 to 30 minutes prior to the needle stick. For superficial dermatologic procedures, Synera should be applied 30 minutes before the procedure.2
The patch must be applied immediately after opening the package and should always be applied to intact skin. The patch should be removed if a burning or irritated sensation occurs.2 In clinical trials, the most common side effects were erythema, blanching, and edema, and these side effects resolved after treatment.1
The use of Synera is contraindicated in patients with a history of sensitivity to lidocaine, tetracaine, para-aminobenzoic acid, or any of the patch's other components. The Synera patch must be removed prior to magnetic resonance imaging.2
Multiple or sequential Synera patches should not be used, nor should the patch be applied for longer than recommended. Even after use, a Synera patch will contain at least 90% of its initial quantity of drug. To avoid accidental overdose, its proper disposal is imperativethe sticky sides must be folded together, and then the patch must be disposed of in a container out of reach of children and pets.2
Synera should be used cautiously in patients with a history of increased sensitivity to any of its components. Patients with severe hepatic disease or pseudocholinesterase deficiency may not be able to adequately metabolize the lidocaine and tetracaine, and therefore may be at increased risk for toxic levels. Synera should not be used on mucous membranes. Avoid contact with the eyes; good hand washing should be practiced after handling the patch to avoid accidental contamination of the eyes. Synera is classified as in Pregnancy Category B.2
Dr. Holmberg is a pharmacist with Phoenix Children's Hospital, Phoenix, Ariz.
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