Action And Clinical Pharmacology: Tetracaine is 2-(dimethylamino) ethyl p-(butylamino) benzoate monohydrochloride. It is a white crystalline odorless powder that is readily soluble in water, physiologic saline solution or dextrose solution. Tetracaine is a local anesthetic of the ester-linkage type, related to procaine. Tetracaine is detoxified by plasma esterases to para-aminobenzoic acid and diethylaminoethanol. tag_IndicationsIndications
Indications And Clinical Uses: Where spinal anesthesia is indicated for operations requiring 2 to 3 hours of anesthesia; for surface anesthesia of the eye, nose and throat.
Tetracaine should be used only on the advice of a physician. Use of ophthalmic tetracaine preparations for self-administration is not recommended.
When applied to the eye tetracaine is less likely than cocaine to affect the corneal epithelium. Usually there is no dilatation of the pupil, except in isolated cases, no disturbance of accommodation, and no increase in intraocular pressure. As with any anesthetic agent, prolonged use in the eye, even in dilute solution is not advisable.
Contra-Indications: In patients with known hypersensitivity to tetracaine or to drugs of a similar chemical configuration (ester-type local anesthetics), or para-aminobenzoic acid or its derivatives; and in patients for whom spinal anesthesia as a technique is contraindicated.
Manufacturers’ Warnings In Clinical States: 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 heart block.
As is the case with any anesthetic agent, prolonged use in the eye, even in dilute solution, is not advisable.
For anesthetizing the larynx, trachea, or esophagus, the total absorbed dose of tetracaine should not usually exceed 20 mg using a 0.5% solution by direct application or a 0.5% solution nebulized for oral inhalation. Absorption may be retarded by the addition of 0.06 mL epinephrine 1:1 000 to each mL of anesthetic solution. In order to avoid rapid absorption and high blood levels of the anesthetic, the solution should not be administered in a coarse stream or by forceful injection, and care should be taken in dose measurement. In every instance, the dose should be measured accurately.
Constitutional reactions following the use of tetracaine have frequently been attributable to an existing allergic hypersensitivity. However, serious untoward effects, some of which proved fatal, have also been due to the injudicious use of excessive doses.
Precautions: The safety and effectiveness of any spinal anesthetic depend upon proper dosage, correct technique, adequate precautions, and readiness for emergencies. The lowest dosage that results in effective anesthesia should be used to avoid high plasma levels and serious systemic side effects. Tolerance varies with the status of the patient; debilitated, elderly patients or acutely ill patients should be given reduced doses commensurate with their weight, age, and physical status. Reduced doses are also indicated for obstetric patients and those with increased intraabdominal pressure.
Protection of the anesthetized eye from irritating chemicals, foreign bodies, and rubbing is very important. Patients should be warned not to rub an eye to which tetracaine has been applied, because inadvertent damage may be done to the anesthetized cornea and conjunctiva.
Tetracaine should be applied more sparingly on open lesions, in cases of allergy, cardiac or hepatic disease, emaciation, hyperthyroidism and other endocrine disorders in which tolerance may be diminished.
Caution should be used in administering tetracaine to patients with abnormal or reduced levels of plasma esterases. Also see package circular.
As is the case with all spinal anesthetics, the patient’s blood pressure should be monitored during anesthesia.
Spinal anesthetics should be used with caution in patients with severe disturbances of cardiac rhythm, shock or heart block.
Tetracaine should not be used if the patient is being treated with a sulfonamide because para-aminobenzoic acid inhibits the action of sulfonamides.
Hypotension should be corrected early if it develops during saddle block for normal vaginal delivery, since hypoxic fetal bradycardia may occur. If a vasoconstrictor is given to correct hypotension, the obstetrician should be cautioned that if an oxytocic drug is employed, severe persistent hypertension and even rupture of a cerebral blood vessel may occur during the postpartum period.
Children: Safety and effectiveness of tetracaine in children have not been established.
There is no evidence from human data that tetracaine may be carcinogenic or mutagenic or that it impairs fertility.
Pregnancy: Tetracaine should be given to a pregnant woman only if clearly needed and the benefits outweigh the risks.
Lactation: It is not known whether or not tetracaine is excreted in human milk. However, it is rapidly metabolized following absorption into the plasma.
Adverse Reactions: Ophthalmology: Prolonged ophthalmic use of topical anesthetics has been associated with corneal epithelial erosions, retardation or prevention of healing of corneal erosions and reports of severe keratitis and permanent corneal opacification and scarring. Inadvertent damage may be done to the anesthetized cornea and conjunctiva by rubbing an eye to which topical anesthetics have been applied. Tetracaine occasionally causes transient smarting in the eye when concentrations higher than 0.5% are used. On rare occasions, local idiosyncratic reactions including lacrimation, photophobia, and chemosis, have been observed. Although exceedingly rare with ophthalmic application of local anesthetics, systemic toxicity, usually manifested as CNS stimulation followed by CNS and cardiovascular depression, may occur.
Rhinolaryngology: Excessive doses of rapid absorption producing high blood levels can result in systemic toxic reactions which can lead to cardiac arrest and death if not promptly and correctly treated. Systemic reactions to tetracaine are characteristic of those associated with other local anesthetics and can involve the central nervous system and cardiovascular system. A small number of reactions may result from hypersensitivity, idiosyncrasy or diminished tolerance to normal dosage.
CNS: 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. Because excitement may be transient or absent, the first manifestation may be drowsiness, sometimes merging into unconsciousness and respiratory and cardiac arrest. Other CNS 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 reactions which may be due to hypersensitivity, idiosyncrasy or diminished tolerance, are characterized by cutaneous lesions (e.g., urticaria), edema, and other manifestations of allergy. Detection of sensitivity by skin testing is of limited value. Severe allergic reactions including anaphylaxis have occurred rarely and are not usually dose related.
Reactions associated with spinal anesthesia techniques: CNS: 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 Systemic Toxic 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 i.v. fluids and, when appropriate, vasopressors (preferably those that stimulate the myocardium). Convulsions are usually controlled with adequate oxygenation alone but i.v. administration in small increments of a barbiturate (preferably an ultrashort-acting barbiturate such as thiopental and thiamylal) or diazepam can be utilized. I.V. barbiturates or anticonvulsant agents should only be administered by those familiar with their use and only if ventilation and oxygenation have first been assured. Muscle relaxants such as succinylcholine may also be required.
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 i.m. or the i.v. route, the dosage of which would depend on the severity of the hypotension and the response to treatment.
Dosage And Administration: Ophthalmology: 0.5% solution: usual dose, 1 or 2 drops. Prolonged use, especially for at-home self-medication by the patient, is not recommended. Epinephrine 1:1 000 may be added to produce vascular constriction when necessary.
Rhinolaryngology: For anesthetizing the larynx, trachea, or esophagus, the total absorbed dose of tetracaine 0.5% solution should not usually exceed 20 mg. Profound anesthesia lasting 30 minutes is obtainable either by direct application of 0.5% solution or by oral inhalation of nebulized 0.5% solution. The addition of 0.06 mL (1 minim) of epinephrine 1:1 000 to each mL of anesthetic solution is advisable to retard absorption and reduce maximum blood levels.
In every instance, special care should be taken to measure the dose accurately.
For a hyperbaric solution Pontocaine Niphanoid is first dissolved in dextrose solution 10% in a ratio of 1 mL dextrose to 10 mg of the anesthetic. Further dilution is made with an equal volume of spinal fluid. The resulting solution now contains 5% dextrose with 5 mg of anesthetic agent per mL.
A hypobaric solution may be prepared by dissolving the Niphanoid in sterile water for injection, USP (1 mg/mL).
Examine ampuls carefully before use. Do no use if discoloration is observed in the ampuls, or if crystals or cloudiness is observed in the reconstituted product. This formulation of sterile tetracaine hydrochloride does not contain preservatives; therefore, unused portions should be discarded and the reconstituted Niphanoid should be used immediately.
Sterilization: The drug in intact ampuls is sterile. The preferred method to destroy bacteria on the exterior of ampuls before opening is heat sterilization (autoclaving). The ampuls should be set in an upright position for autoclaving. Immersion in antiseptic solution is not recommended.
Autoclave at 15 pounds pressure, at 121Â°C, for 15 to 20 minutes. The crystals may lose their snow-like appearance and tend to adhere to the sides of the ampul. This effect may slightly decrease the rate at which the drug dissolves but does not interfere with its anesthetic potency.
Autoclaving increases the likelihood of crystal formation. Unused autoclaved ampuls should be discarded. In no case should unused autoclaved ampuls be placed back in stock for later use.
Availability And Storage: Ampuls: Each ampul of dry powder contains: tetracaine HCl 20 mg. Gluten-, lactose-, preservative-, starch and sulfite-free. Ampuls of 20 mg, boxes of 10. Protect ampuls from light.
Ophthalmic Solution: Each mL of ophthalmic solution contains: tetracaine HCl 0.5% in purified water. Nonmedicinal ingredients: chlorobutanol (hydrous) and sodium chloride. Mono-Drop bottles of 15 mL.
PONTOCAINE® Sanofi Tetracaine HCl Anesthetic