Tetracaine HCL

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

Dosage and Administration As with all anesthetics, the dosage varies and depends upon the area to be anesthetized, the number of neuronal segments to be blocked, individual tolerance, and the technique of anesthesia. The lowest dosage needed to provide effective anesthesia should be administered. For specific techniques and procedures, refer to standard textbooks. Suggested Dosage for Spinal Anesthesia Using 1% Tetracaine HCl Injection, USP Extent of Anesthesia Dose of solution (mL) Volume of spinal fluid (mL) Site of injection (lumbar interspace) Perineum 0.5 (= 5 mg)* 0.5 4 th Perineum and lower extremities 1.0 (= 10 mg) 1.0 3 rd or 4 th Up to costal margin(= 15 mg to 20 mg)** 1.5 to 2.0 1.5 to 2.0 2 nd , 3 rd , or 4 th * For vaginal delivery (saddle block), from 2 mg to 5 mg in dextrose. **Doses exceeding 15 mg are rarely required and should be used only in exceptional cases. Inject solution at rate of about 1 mL per 5 seconds. The extent and degree of spinal anesthesia depend upon dosage, specific gravity of the anesthetic solution, volume of solution used, force of the injection, level of puncture, position of the patient during and immediately after injection, etc. When spinal fluid is added to 1% tetracaine hydrochloride injection, some turbidity results, the degree depending on the pH of the spinal fluid, the temperature of the solution during mixing, as well as the amount of drug and diluent employed. Liberation of base (which is completed within the spinal canal) is held to be essential for satisfactory results with any spinal anesthetic. The specific gravity of spinal fluid at 25°C/25°C varies under normal conditions from 1.0063 to 1.0075. The 1% concentration in saline solution has a specific gravity of 1.0060 to 1.0074 at 25°C/25°C. A hyperbaric solution may be prepared by mixing equal volumes of the 1% solution and Dextrose Solution 10%. Examine vials carefully before use. Do not use solution if crystals, cloudiness, or discoloration is observed. This formulation of tetracaine hydrochloride does not contain antimicrobial or bacteriostatic agents; therefore, unused portions should be discarded. Sterilization of Vials The tetracaine hydrochloride injection is sterile within an undamaged vial. To destroy bacteria on the exterior of vials use heat sterilization (autoclaving) before opening. Immersion in antiseptic solution is not recommended. Autoclave at 15-pounds pressure, at 121°C (250°F), for 15 minutes. Autoclaving increases likelihood of crystal formation. Unused autoclaved vials should be discarded. Under no circumstances should unused vials which have been autoclaved be returned to stock .

CONTRAINDICATIONS: 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.

WARNINGS 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.

ADVERSE REACTIONS 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. The extent of the hypotension will usually depend on the number of dermatomes blocked. The blood pressure should therefore be monitored in the early phases of anesthesia. If hypotension occurs, it is readily controlled by vasoconstrictors administered either by the intramuscular or the intravenous route, the dosage of which would depend on the severity of the hypotension and the response to treatment.