tetracaine

Action and Spectrum

Mechanism of action 

tetracaine is a local anaesthetic that works by blocking the conduction of nerve impulses. It is an amide-type local anaesthetic. It acts on the voltage-gated sodium channels in the nerve cells, preventing the influx of sodium ions and thus preventing the initiation and conduction of nerve impulses. 

Spectrum 

The spectrum of activity of tetracaine includes both topical and regional anaesthesia. Topically, it is used in ophthalmology and otolaryngology to numb the surface of the eye or ear. Regionally, it is used as a spinal or epidural anaesthetic and local infiltration anaesthetic. It is also used as a component in some dental anaesthetics. 

Drug Interaction

Adverse Reaction

Frequency undefined:  

Restlessness 

Dizziness 

Conjunctival redness 

Photophobia 

Twitching 

Unconsciousness 

Nausea 

Tinnitus 

Hypotension 

Tremors 

Anxiety 

Nervousness 

Blurred vision 

Lacrimation 

Chills 

Myocardial infarction 

Cardiac arrest 

Black Box Warning

Contraindication / Caution

Contraindications 

• Hypersensitivity to tetracaine or any other local anesthetics of the amide-type 
• Known or suspected disorders of the heart, such as a history of heart attack, heart failure, or heart rhythm disorders 
• Known or suspected disorders of the blood vessels, such as poor circulation 
• Known or suspected disorders of the liver or kidneys 
• Known or suspected disorders of the nervous system, such as seizures or a history of seizures 
• Pregnancy and lactation 
• Patients with a history of methemoglobinemia or congenital or acquired deficiency of methemoglobin reductase 
• Tetracaine should not be used in spinal anesthesia in patients with severe hypertension or severe preeclampsia 

Caution 

• It should be used cautiously in patients with allergies or hypersensitivity to local anesthetics. 
• It should be used with caution in patients with a history of heart disease or blood vessel disease, as it may affect the heart and blood vessels. 
• It should be used cautiously in elderly patients, as they may be more sensitive to the drug’s effects. 
• It should be used with caution in patients with liver or kidney disease, as it may affect the liver or kidneys. 
• It should be used with caution in patients with a history of seizures or methemoglobinemia. 
• It should be used cautiously in pregnancy and lactation, as it may cross the placenta or be present in breast milk. 
• It should be used with caution in patients with severe hypertension or severe preeclampsia. 
• It should be used with caution in patients with spinal anesthesia, as its use may cause hypotension. 
• It should be used with caution in patients taking other medications, especially those that may interact with tetracaine 

Pregnancy / Lactation

Pregnancy consideration: Insufficient data available 

Lactation: Excretion of the drug in human breast milk is unknown 

Pregnancy category: 

Category A: well-controlled and Satisfactory studies show no risk to the fetus in the first or later trimester.   

Category B: there was no evidence of risk to the fetus in animal studies, and there were not enough studies on pregnant women. 

Category C: there was evidence of risk of adverse effects in animal reproduction studies, and no adequate evidence in human studies must take care of potential risks in pregnant women.    

Category D: adequate data available with sufficient evidence of human fetal risk from various platforms, but despite the potential risk, and used only in emergency cases for potential benefits.    

Category X: Drugs listed in this category outweigh the risks over benefits. Hence these categories of drugs need to be avoided by pregnant women.    

Category N: There is no data available for the drug under this category. 

Pharmacology

Pharmacology 

Local anaesthetics such as tetracaine work by inhibiting the conduction of nerve impulses. They do this by binding to and blocking the voltage-gated sodium channels in nerve cells. By blocking the influx of sodium ions, they prevent the initiation and conduction of nerve impulses. This reduces the sensitivity of the nerve fibres to stimulus, thereby producing a loss of sensation in the area where the anaesthetic is applied. In addition, local anaesthetics can increase the action potential threshold, meaning that a more potent stimulus is required to activate the nerve fibres. This further contributes to the loss of sensation in the area where the anaesthetic is applied. 

Pharmacodynamics 

It is a local anaesthetic of the amide-type. It binds to the voltage-gated sodium channels in nerve cells, which are responsible for the initiation and conduction of nerve impulses. By binding to these channels, tetracaine blocks the influx of sodium ions, preventing the initiation and conduction of nerve impulses. This reduces the sensitivity of the nerve fibres to stimulus, thereby producing a loss of sensation in the area where the anaesthetic is applied. 

It also increases the action potential threshold, meaning a more potent stimulus is required to activate the nerve fibres. This further contributes to the loss of sensation in the area where the anaesthetic is applied. 

Pharmacokinetics 

Absorption 

The onset of action of tetracaine is typically within 5 to 10 minutes, and the duration of action is typically 2 to 3 hours 

Distribution 

It is highly protein bound, meaning that a significant portion of the drug binds to proteins in the blood. This can affect the distribution and elimination of the drug.  

Metabolism 

It is metabolized in the liver, and its metabolism produces both ester- and amide-type local anesthetics. 

Elimination/excretion 

Excretion of tetracaine mainly occurs via urine. The drug is eliminated primarily unchanged, but small amounts of metabolites may also be present in the urine 

Adminstartion

Administration 

It is a local anesthetic typically administered through injection, topical application, or spinal or epidural injection. The specific method of administration and dosage will depend on the procedure being performed and the patient’s age, weight, and overall health. It is essential to follow the dosage and administration instructions a healthcare provider provides. 

When administered by injection, the solution should be injected slowly and with caution to avoid excessive bleeding or tissue damage. When applied topically, it should be applied to the skin area that will be numbed, usually with a cotton swab or a dropper. 

It can have side effects such as allergic reactions, nausea, and drowsiness, so it is essential to consult a healthcare provider before taking tetracaine. 

Patient Information Leaflet

Patient information leaflet 

Generic Name: tetracaine 

Pronounced: (TET-ruh-kane) 

Why do we use tetracaine? 

It is a local anesthetic that is used to numb a specific area of the body. It is used for a variety of procedures, such as: 

• Dental procedures: It is used to numb the gums and mouth for dental procedures, such as filling cavities or performing extractions. 
• Eye procedures: A local anesthetic for eye procedures, such as cataract surgery or corneal transplants. 
• Topical anesthesia is used as a topical cream or gel to numb the skin before minor surgical procedures, such as suturing cuts or removing moles. 
• Epidural anesthesia is used as a spinal injection to relieve pain during labor and delivery. 
• Lumbar puncture: It is used as a local anesthetic during the lumbar puncture procedure