Warnings for Synera
Included as part of the PRECAUTIONS section.
Precautions for Synera
Methemoglobinemia
Cases of methemoglobinemia have been reported in association with local anesthetic use. Although all patients are at risk for methemoglobinemia, patients with glucose-6-phosphate dehydrogenase deficiency, congenital or idiopathic methemoglobinemia, cardiac or pulmonary compromise, infants under 6 months of age, and concurrent exposure to oxidizing agents or their metabolites are more susceptible to developing clinical manifestations of the condition. If local anesthetics must be used in these patients, close monitoring for symptoms and signs of methemoglobinemia is recommended.
Signs of methemoglobinemia may occur immediately or may be delayed some hours after exposure, and are characterized by a cyanotic skin discoloration and/or abnormal coloration of the blood. Methemoglobin levels may continue to rise; therefore, immediate treatment is required to avert more serious central nervous system and cardiovascular adverse effects, including seizures, coma, arrhythmias, and death. Discontinue SYNERA and any other oxidizing agents. Depending on the severity of the signs and symptoms, patients may respond to supportive care, i.e., oxygen therapy, hydration. A more severe clinical presentation may require treatment with methylene blue, exchange transfusion, or hyperbaric oxygen.
Overexposure
Application of a SYNERA patch for longer duration than recommended, or the simultaneous or sequential application of multiple SYNERA patches, could result in sufficient absorption of lidocaine and tetracaine to result in serious adverse effects [see OVERDOSAGE].
Storage And Disposal
Used SYNERA patches contain a large amount of lidocaine and tetracaine (at least 90% of the initial amount). The potential exists for a child or pet to suffer serious adverse effects from chewing or ingesting a new or used SYNERA patch. It is important for patients to store and dispose of SYNERA out of the reach of children and pets.
Avoidance Of Exposure To Eyes and Mucous Membranes
- Contact of SYNERA with the eyes should be avoided based on the findings of severe eye irritation with the use of similar products in animals. Also, the loss of protective reflexes may predispose to corneal irritation and potential abrasion. If eye contact occurs, immediately wash out the eye with water or saline and protect the eye until sensation returns.
- SYNERA is not recommended for use on mucous membranes or on areas with a compromised skin barrier because these uses have not been studied. Application to broken or inflamed skin may result in toxic blood concentrations of lidocaine and tetracaine from increased absorption.
Magnetic Resonance Imaging
The integrated heating component contains iron powder; therefore, the SYNERA patch must be removed before a patient undergoes magnetic resonance imaging.
Allergic Reactions
Allergic or anaphylactoid reactions associated with lidocaine, tetracaine, or other components of SYNERA can occur. They are characterized by urticaria, angioedema, bronchospasm, and shock. If an allergic reaction occurs, it should be managed by conventional means.
Special Patient Populations
- SYNERA should be used with caution in patients who may be more sensitive to the systemic effects of lidocaine and tetracaine particularly the acutely ill or debilitated.
- Patients with severe hepatic disease or pseudocholinesterase deficiency, because of their inability to metabolize local anesthetics normally, are at a greater risk of developing toxic plasma concentrations of lidocaine and tetracaine.
Vaccinations
Lidocaine has been shown to inhibit viral and bacterial growth. The effect of SYNERA on intradermal injections of live vaccines has not been determined.
Patient Counseling Information
- Advise patients to read the FDA-approved patient labeling (Instructions for Use).
- Advise patients that SYNERA is a patch containing two medicines (lidocaine and tetracaine) that are known as local anesthetics, and a heating component. These medicines are used to lessen the pain associated with superficial venous access and superficial dermatological procedures such as excision, electrodessication and shave biopsy of skin lesions.
- Advise patients that SYNERA should be applied immediately after opening the pouch. Instruct patients to not cut or remove the top cover of the patch as this could result in thermal injury.
- Advise patients that keeping a patch on longer than recommended or applying multiple patches simultaneously or sequentially could result in systemic absorption sufficient to result in serious adverse effects that are typical of drugs in this class.
- Advise patients that the patch must be removed before magnetic resonance imaging.
- Advise patients that SYNERA is contraindicated in patients with a known history of sensitivity to lidocaine, tetracaine, local anesthetics of the amide or ester type, or any other component of the product and in patients with para-aminobenzoic acid (PABA) hypersensitivity.
- Advise patients that SYNERA should be used with caution in patients who may be more sensitive to the systemic effects of lidocaine and tetracaine, including the acutely ill, the debilitated, and those with compromised hepatic function. Patients with severe hepatic disease or pseudocholinesterase deficiency are at greater risk of developing toxic plasma concentrations.
- Advise patients that SYNERA should be used with caution in patients receiving class I antiarrhythmics and/or other local anesthetics, because the systemic toxic effects may be additive and potentially synergistic with lidocaine and tetracaine.
- Advise patients not to use SYNERA if they have a history of methemoglobinemia.
- Inform patients that use of local anesthetics may cause methemoglobinemia, a serious condition that must be treated promptly. Advise patients or caregivers to stop use and seek immediate medical attention if they or someone in their care experience the following signs or symptoms: pale, gray, or blue colored skin (cyanosis); headache; rapid heart rate; shortness of breath; lightheadedness; or fatigue.
- Advise patients to avoid contact of SYNERA with the eyes due to potential irritation or abrasion. If contact occurs, immediately wash the eye with water or saline, and protect it until sensation returns.
- Advise patients that SYNERA should only be applied to intact skin. Inform patients that exposure of the skin to SYNERA may result in erythema, blanching and edema; these reactions are generally mild, resolving spontaneously soon after the patch is removed.
- Advise patients that SYNERA is not for use on mucous membranes or on areas with broken skin.
- Advise patients that if skin irritation or a burning sensation occurs during application, the product should be removed.
- Inform patients of the signs of an allergic or anaphylactoid reaction (urticaria, angioedema, bronchospasm, and shock). Instruct patients to seek immediate emergency help if these occur.
- Advise patients that SYNERA may lead to diminished or blocked sensation in the treated skin; therefore, patients should avoid inadvertent trauma (rubbing, scratching, or exposure to heat or cold) before complete sensation returns.
- Advise patients to contact their healthcare professional if they don’t recall where to apply the patch.
- Instruct patients to store SYNERA and to discard used patches out of the reach of children and pets.
- The effect of SYNERA on intradermal injections of live vaccines has not been determined.
- Advise breastfeeding women not to apply SYNERA directly to the nipple and areola to avoid direct infant exposure [see Use In Specific Populations].
Nonclinical Toxicology
Carcinogenesis, Mutagenesis, Impairment Of Fertility
Carcinogenesis -Long-term studies in animals have not been performed to evaluate the carcinogenic potential of either lidocaine or tetracaine.
Mutagenesis
The mutagenic potential of lidocaine base and tetracaine base has been determined in the in vitro Ames Bacterial Reverse Mutation Assay, the in vitro chromosome aberration assay using Chinese hamster ovary cells, and the in vivo mouse micronucleus assay. Lidocaine was negative in all three assays. Tetracaine was negative in the in vitro Ames assay and the in vivo mouse micronucleus assay. In the in vitro chromosome aberration assay, tetracaine was negative in the absence of metabolic activation, and equivocal in the presence of metabolic activation.
Impairment Of Fertility
Lidocaine did not affect fertility in female rats when given via continuous subcutaneous infusion via osmotic minipumps up to doses of 250 mg/kg/day (1500 mg/m² or 35 times the SDA on a mg/m² basis). Although lidocaine treatment of male rats increased the copulatory interval and lead to a dose-related decreased homogenization resistant sperm head count, daily sperm production, and spermatogenic efficiency, the treatment did not affect overall fertility in male rats when given subcutaneous doses up to 60 mg/kg (360 mg/m² or 8 times the SDA on a mg/m² basis). Tetracaine did not affect fertility in male or female rats when given subcutaneous doses up to 7.5 mg/kg (45 mg/m² or 1 times the SDA on a mg/m² basis). Multiples of exposure are based on an SDA of 70 mg each of lidocaine and tetracaine in SYNERA patch for 30 minutes to a 60 kg person (43 mg/m²).
Use In Specific Populations
Pregnancy
Risk Summary
There are no available data on SYNERA use in pregnant women to determine a drug-associated risk of major birth defects, miscarriage, or adverse maternal or fetal outcomes. Available data from an epidemiologic study and case series with parenteral lidocaine use in pregnant women have not identified a drug-associated risk of major birth defects, miscarriage, or other adverse maternal or fetal outcomes. Published data on tetracaine use in pregnant women are not sufficient to determine any drug-associated risks. The amount of lidocaine and tetracaine systemically absorbed from SYNERA is low compared to the parenteral route of administration and is not expected to result in significant fetal exposure. Systemic exposure of SYNERA is directly related to both the duration of application and the surface area over which it is applied [see CLINICAL PHARMACOLOGY].
In an animal reproduction study, pregnant rats administered lidocaine, containing 1:100,000 epinephrine, injected into the masseter muscle of the jaw or into the gum of the lower jaw on Gestation Day 11 at 0.8 times the Single Dermal Administration (SDA) resulted in developmental delays in neonates. Subcutaneous administration of tetracaine to pregnant rats and rabbits did not produce adverse embryofetal effects at 1 times the SDA when administered during the period of organogenesis (see Data).
The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2 to 4% and 15 to 20%, respectively.
Data
Animal Data
Lidocaine was not teratogenic in rats given subcutaneous doses up to 60 mg/kg (360 mg/m² or 8 times the SDA on a mg/m² basis) or in rabbits up to 15 mg/kg (180 mg/m² or 4 times the SDA on a mg/m² basis) during the period of organogenesis. Tetracaine was not teratogenic in rats given subcutaneous doses up to 10 mg/kg (60 mg/m² or 1 times the SDA on a mg/m² basis) or in rabbits up to 5 mg/kg (60 mg/m² or 1 times the SDA on a mg/m² basis) during the period of organogenesis. SYNERA components (lidocaine and tetracaine) given as a 1:1 eutectic mixture during the period of organogenesis were not teratogenic in rats (60 mg/m² or 1 times the SDA on a mg/m² basis) or rabbits (120 mg/m² or 3 times the SDA on a mg/m² basis).
Lidocaine, containing 1:100,000 epinephrine, at a dose of 6 mg/kg (36 mg/m² or 0.8 times the SDA on a mg/m² basis) injected into the masseter muscle of the jaw or into the gum of the lower jaw of Long-Evans hooded pregnant rats on Gestation Day 11 led to developmental delays in neonatal behavior among offspring. Developmental delays were observed for negative geotaxis, static righting reflex, visual discrimination response, sensitivity and response to thermal and electrical shock stimuli, and water maze acquisition. The developmental delays of the neonatal animals were transient with responses becoming comparable to untreated animals later in life. The clinical relevance of the animal data is uncertain.
In a published study, lidocaine administered to pregnant rats by continuous subcutaneous infusion during the period of organogenesis at 100, 250, and 500 mg/kg/day, did not produce any structural abnormalities, but did result in lower fetal weights at 500 mg/kg/day dose (3000 mg/m² or 69 times the SDA on a mg/m² basis) in the absence of maternal toxicity.
Pre- and postnatal maturational, behavioral, or reproductive development was not affected by maternal subcutaneous administration of tetracaine during gestation and lactation up to doses of 7.5 mg/kg (45 mg/m² or 1 times the SDA on a mg/m² basis).
Lactation
Risk Summary
There are no data on the presence of tetracaine in human milk, the effects on the breastfed infant, or the effect on milk production. Published studies on parenterally administered lidocaine have reported the presence of lidocaine in human milk with milk:plasma ratios ranging between 0.4 to 1.1. Available data on lidocaine’s effects on the breastfed child have not revealed a consistent pattern of associated adverse effects. The amount of lidocaine present in human milk following topical administration is unknown, but systemic absorption from topical lidocaine is low [see CLINICAL PHARMACOLOGY].
The developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for SYNERA and any potential adverse effects on the breastfed child from SYNERA or from the underlying maternal condition.
Clinical Considerations
Minimizing Exposure
Advise breastfeeding women not to apply SYNERA directly to the nipple and areola to avoid direct infant exposure.
Pediatric Use
The safety and effectiveness of SYNERA have been established in pediatric patients 3 years and older based on adequate and well-controlled studies [see Clinical Studies]. While efficacy has not been established for children less than 3 years of age, the safety of SYNERA in infants has been evaluated in one study in which 34 infants 4 to 6 months of age received SYNERA. The recommended application time for the patch for pediatric patients is the same as for adults. Simultaneous or sequential application of more than two SYNERA patches to children is not recommended as it has not been adequately studied.
Use In Geriatric Patients
In the controlled clinical studies, 139 patients over 65 years of age, including 41 patients over 75 years of age, received SYNERA. Visual Analog Scale (VAS) pain score differences between SYNERA and placebo were considerably lower in the geriatric subjects than in the rest of the adult population. No overall differences in safety were observed between geriatric subjects and younger subjects. However, increased sensitivity in individual patients greater than 65 years of age cannot be ruled out. After intravenous dosing, the elimination half-life of lidocaine is significantly longer in elderly patients (2.5 hours) than in younger patients (1.5 hours).