Tetracaine

BRAND NAMES

Brand names for tetracaine include Altacaine, Opticaine, Viractin, TetraVisc, Minims (Amethocaine), and Pontocaine.

 It is a potent, long-acting local anesthetic used topically for the eye or skin and via injection for spinal anesthesia. All applications must be supervised by a healthcare provider. 

MECHANISM OF ACTION

Tetracaine works as a local anesthetic by blocking the transmission of nerve impulses through inhibition of voltage-gated sodium channels in nerve cell membranes. It first enters the neuron in its non-ionized form, then becomes ionized and binds to the intracellular α subunit of the sodium (Na⁺) channel. This binding prevents sodium ions from entering the cell, thereby halting depolarization and the generation of action potentials. As a result, pain signal transmission is blocked, leading to localized numbness.

PHARMACOKINETICS

Absorption

Tetracaine is a potent, lipid-soluble local anesthetic that is absorbed differently depending on the application site. Absorption is most rapid and significant through mucous membranes or open wounds, but minimal through intact skin. This variability directly influences its potential for systemic toxicity. 

Distribution

Tetracaine has a relatively large volume of distribution (Vd) because of its high lipid solubility, enabling it to penetrate and distribute widely throughout body tissues.

Metabolism

Tetracaine is predominantly metabolized in the plasma through hydrolysis by pseudocholinesterase, also referred to as butyrylcholinesterase. This enzymatic reaction breaks tetracaine down into para-aminobenzoic acid (PABA) and a compound similar to diethylaminoethanol.

Excretion

Tetracaine is an ester-type local anesthetic that is primarily excreted in the urine following its metabolism.

PHARMACODYNAMICS

Tetracaine’s pharmacodynamics involve the inhibition of voltage-gated sodium channels in nerve cell membranes, blocking the influx of sodium ions and preventing depolarization. This action disrupts nerve impulse conduction, leading to localized anesthesia and a temporary loss of sensation.

ADMINISTRATION

Tetracaine administration is a medical procedure performed by a healthcare provider for local anesthesia. The route and dosage vary depending on the procedure and the area being treated, including topical administration for the eyes and skin, and injection for spinal anesthesia. 

DOSAGE AND STRENGTH

Tetracaine, a potent local anesthetic, is available in several dosage forms for topical and injectable use. The form depends on the area of the body being numbed and the medical procedure being performed. The standard adult dose of tetracaine hydrochloride is typically 5 mg.

DRUG INTERACTIONS

Tetracaine can interact with other medications, increasing the risk of adverse effects. When combined with drugs such as sulfonamides, nitroglycerin, or other oxidizing agents, there is an elevated risk of methemoglobinemia. Additionally, it may enhance central nervous system (CNS) depression when used alongside benzodiazepines, potentially leading to increased sedation or respiratory depression.

FOOD INTERACTIONS

The research found no known food interactions with tetracaine, but there are certain drug and medical condition interactions to be aware of. Tetracaine is typically used as a topical anesthetic, and it is not an oral medication, which minimizes the risk of food interactions.

CONTRAINDICATIONS

Tetracaine is contraindicated for patients with hypersensitivity to tetracaine or other ester-type anesthetics and should not be used with sulfonamide medications. The contraindications can also vary depending on the specific formulation and intended use.

SIDE EFFECTS

• Burning, stinging, and blurred vision.

• Itching, redness, tearing, ocular pain, and sensitivity to light.

• Corneal damage, corneal opacification (clouding), and eye infections. 

• Methemoglobinemia.

• Allergic reactions.

• Central nervous system (CNS) effects.

• Cardiovascular effects.

• Spinal anesthesia complications.

OVER DOSE

• Seizures.

• Neurological Symptoms.

• irregular heartbeats.

• lack of pulse or blood pressure. 

• Respiratory Symptoms.

• A change in consciousness, pale, gray, or blue-colored skin, lips, or nails. 

TOXICITY

Tetracaine toxicity, also known as Local Anesthetic Systemic Toxicity (LAST), is a rare but life-threatening complication that occurs when a high concentration of the anesthetic is absorbed into the bloodstream. Tetracaine is more potent and toxic than other local anesthetics, and the risk of toxicity increases with higher doses or rapid absorption.