Tetracaine HCL

Tetracaine hydrochloride is indicated for the production of spinal anesthesia for procedures requiring two to three hours.

Spinal anesthesia with tetracaine hydrochloride is contraindicated in patients with known hypersensitivity to tetracaine hydrochloride or to drugs of a similar chemical configuration (ester-type local anesthetics), or aminobenzoic acid or its derivatives; and in patients for whom spinal anesthesia as a technique is contraindicated. The decision as to whether or not spinal anesthesia should be used for an individual patient should be made by the physician after weighing the advantages with the risks and possible complications.

Contraindications to spinal anesthesia as a technique can be found in standard reference texts, and usually include generalized septicemia, infection at the site of injection, certain diseases of the cerebrospinal system, uncontrolled hypotension, etc.

RESUSCITATIVE EQUIPMENT AND DRUGS SHOULD BE IMMEDIATELY AVAILABLE WHENEVER ANY LOCAL ANESTHETIC DRUG IS USED. Large doses of local anesthetics should not be used in patients with heartblock. Reactions resulting in fatality have occurred on rare occasions with the use of local anesthetics, even in the absence of a history of hypersensitivity. 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 tetracaine hydrochloride 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.

Systemic adverse reactions to tetracaine hydrochloride are characteristic of those associated with other local anesthetics and can involve the central nervous system and the cardiovascular system. Systemic reactions usually result from high plasma levels due to excessive dosage, rapid adsorption, or inadvertent intravascular injection. A small number of reactions to tetracaine hydrochloride may result from hypersensitivity, idiosyncrasy or diminished tolerance to normal dosage.

Central nervous system effects are characterized by excitation or depression. The first manifestation may be nervousness, dizziness, blurred vision, or tremors, followed by drowsiness, convulsions, unconsciousness and possibly respiratory and cardiac arrest. Since excitement may be transient or absent, the first manifestation may be drowsiness, sometimes merging into unconsciousness and respiratory and cardiac arrest.

Other central nervous system effects may be nausea, vomiting, chills, constriction of the pupils, or tinnitus. Cardiovascular system reactions include depression of the myocardium, blood pressure changes (usually hypotension), and cardiac arrest. Allergic reaction s, which may be due to hypersensitivity, idiosyncrasy, or diminished tolerance, are characterized by cutaneous lesions (eg. urticaria), edema, and other manifestations of allergy.

Detection of sensitivity by skin testing is of limited value. Severe allergic reactions including anaphylaxis have rarely occurred and are not usually dose-related. Reactions Associated with Spinal Anesthesia Techniques: Central Nervous System : post-spinal headache, meningismus, arachnoiditis, palsies, or spinal nerve paralysis. Cardiovascular: hypotension due to vasomotor paralysis and pooling of the blood in the venous bed.

Respiratory: respiratory impairment or paralysis due to the level of anesthesia extending to the upper thoracic and cervical segments. Gastrointestinal : nausea and vomiting. Treatment of Reactions: Toxic effects of local anesthetics require symptomatic treatment; there is no specific cure. The most important measure is oxygenation of the patient by maintaining an airway and supporting ventilation. Supportive treatment of the cardiovascular system includes intravenous fluids and, when appropriate, vasopressors (preferably those that stimulate the myocardium).

Convulsions are usually controlled with adequate oxygenation alone but intravenous administration in small increments of a barbiturate (preferably an ultrashort-acting barbiturate such as thiopental and thiamylal), or diazepam can be utilized. Intravenous barbiturates or anticonvulsant agents should only be administered by those familiar with their use and only if ventilation and oxygenation have first been assured. In spinal anesthesia, sympathetic blockade also occurs as a pharmacological action, resulting in peripheral vasodilation and often hypotension.