warnings and cautions
Excessive dosage or short intervals 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 their prescription label. The management of serious adverse reactions may require the use of resuscitative equipment, oxygen, or other resuscitative drugs. 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 for some hours after exposure and are characterized by 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® ES 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. Accidental Exposure in Children Even a used Lidothol® ES 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® ES. However, the risk with this formulation has not been evaluated. It is important for patients to store and dispose of Lidothol® ES beyond the reach of children, pets, and others. (See HANDLING AND DISPOSAL) Excessive Dosing Excessive dosing by applying Lidothol® ES 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 rate of systemic absorption and elimination determines the blood concentration of lidocaine. Longer duration of application, application of more than the recommended number of systems, smaller patients, or impaired elimination may all contribute to increasing the blood concentration of lidocaine. With recommended dosing of Lidothol® ES, the average blood concentration is about 0.13 µg/mL, but concentrations higher than 0.25 µg/mL have been observed in some patients. Sedation and Impaired Alertness Because of the possibility of sedation, patients should be cautioned regarding the use of heavy machinery or automobiles, or 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® ES should be used with caution in patients with a history of drug sensitivities, especially if the etiologic agent is uncertain. Allergic and anaphylactoid reactions associated with lidocaine, although rare, can occur. They are characterized by angioedema, bronchospasm, dermatitis, dyspnea, hypersensitivity, laryngospasm, pruritus, shock, and urticaria. If they occur, consult your doctor. Non-intact Skin Although not tested, application to broken or inflamed skin may result in higher blood concentrations of lidocaine from increased absorption. Lidothol® ES is only recommended for use on intact skin. Eye Exposure The contact of Lidothol® ES with the 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 Lidothol® ES is not recommended, as this has not been evaluated and may increase plasma lidocaine levels.