warnings and cautions
Warnings and Precautions 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 and symptoms of methemoglobinemia may occur immediately or may be delayed some hours after exposure and are characterized by a cyanotic skin discoloration and 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 Lidothol and any other oxidizing agents. Depending on the severity of the symptoms, patients may respond to supportive care, i.e., oxygen therapy, hydration. More severe symptoms may require treatment with methylene blue, exchange transfusion, or hyperbaric oxygen. Excessive dosage or short interval between doses can result in high plasma levels and serious adverse effects. Patients should be instructed to strictly adhere to the recommended dosage and administration guidelines set forth in this literature and on your prescription label. The management of serious adverse reactions may require the use of resuscitative equipment, oxygen or other resuscitative drugs. Accidental Exposure in Children Even a used Lidothol patch contains a large amount of Lidocaine. The potential exists for a small child or a pet to suffer serious adverse effects from chewing or ingesting a new or used Lidothol patch, although the risk with this formulation has not been evaluated. It is important for patients to store and dispose of Lidothol beyond the reach of children, pets and others. (See HANDLING AND DISPOSAL) Excessive Dosing Excessive dosing by applying Lidothol to larger areas for longer than the recommended wearing time could result in increased absorption of Lidocaine and high blood concentrations, leading to serious adverse effects. Lidocaine toxicity could be expected at Lidocaine blood concentrations above 5 µg/mL. The blood concentration of Lidocaine is determined by the rate of systemic absorption and elimination. Longer duration of application, application of more than the recommended number of patches, smaller patients, or impaired elimination may all contribute to increasing the blood concentration of Lidocaine. With recommended dosing of Lidothol, the average blood concentration is about 0.13 µg/mL, but concentration higher than 0.25 µg/mL have been observed in some patients. Because of the possibility of sedation, patients should be cautioned regarding the use of heavy machinery or automobiles, also any activities made hazardous by decreased alertness. Hepatic Disease Patients with severe hepatic disease are at greater risk of developing toxic blood concentrations of Lidocaine, because of their inability to metabolize Lidocaine normally. Allergic Reactions Patients allergic to para-‐aminobenzoic acid derivatives (procaine, tetracaine, benzocaine, etc.) have not shown cross sensitivity to Lidocaine. However, Lidothol should be used with caution in patients with a history of drug sensitivities, especially if the etiologic agent is uncertain. Non-intact Skin Application to broken or inflamed skin, although not tested, may result in higher blood concentrations of Lidocaine from increased absorption. Lidothol is only recommended for use on intact skin. Eye Exposure The contact of Lidothol with eyes, although not studied, should be avoided based on the findings of severe eye irritations with the use of similar products in animals. If eye contact occurs, immediately wash out the eye with water or saline and protect the eye until sensation returns. External Heat Sources Placement of external heat sources, such as heating pads or electric blankets, over patches is not recommended as this has not been evaluated and may increase plasma Lidocaine levels. Drug Interactions: Antiarrhythmic Drugs Lidothol should be used with caution in patients receiving Class 1 antiarrhythmic drugs (such as tocainide and mexiletine) since the toxic effects are additive and potentially synergistic. Local Anesthetics When Lidothol is used concurrently with other products containing local anesthetic agents the amount absorbed from all formulations must be considered. Carcinogenesis, Mutagenesis, Impairment of Fertility Carcinogenesis A minor metabolite, 2,6-‐xylidine, has been found to be carcinogenic in rats. The blood concentration of this metabolite is negligible following application of Lidothol Mutagenesis Lidocaine is not mutagenic in Salmonella/mammalian microsome test nor clastogenic in chromosome aberration assay with human lymphocytes and mouse micronucleus test. Impairment of Fertility The effect of Lidothol on fertility has not been studied. PREGNANCY: The safety of Lidothol has not been established during pregnancy. There are no well-‐controlled studies in pregnant women. Lidothol should not be used during pregnancy unless absolutely needed. Discuss with physician prior to using Lidothol during pregnancy. NURSING MOTHERS: The effect of Lidothol on the nursing infant has not been evaluated. Lidothol has not been studied in nursing mothers. Caution should be exercised when Lidothol is administered to a nursing mother. PEDIATRIC/GERIATRIC USE: Safety and effectiveness in pediatric and geriatric patients have not been established.