Pharmacology · Local anesthetics
Tetracaine !
Potent, long-acting ester local anaesthetic: eye drops for ocular procedures and an option for spinal anaesthesia.
Updated 2026-11-01
Also called: Amethocaine, Tetracaine hydrochloride
Mechanism of action
Tetracaine, an amino ester, blocks voltage-gated sodium channels in nerve endings and fibres, so pain impulses are neither generated nor conducted. Applied to the eye, it numbs the cornea and conjunctiva quickly. It is more potent and longer-acting than procaine; it is metabolised more slowly than other esters, which raises its systemic toxicity if much is absorbed.
- Penetrates the nerve membrane
- Blocks the sodium channel from inside
- The cornea or area stops transmitting pain
- Plasma cholinesterase hydrolyses it (more slowly than other esters)
Pharmacokinetics
- Absorption
- Topical on the cornea or mucosa, or injected into the subarachnoid space.
- Metabolism
- Hydrolysis by plasma esterases (cholinesterase), slower than for other esters.
- Elimination
- Kidney, as metabolites.
Indications
- Rapid, short topical ocular anaesthesia for procedures in clinic or emergency
- Examination of the painful eye, for example a corneal abrasion, without giving the drops to the patient Corneal abrasion and ocular foreign body →
- Long-acting spinal anaesthesia
Adverse effects
Common
- Burning and stinging on application
- Conjunctival redness and irritation
- Transient eye pain
Contraindications
- Hypersensitivity to tetracaine or ester-type anaesthetics
- Intracameral use (inside the eye)
Key interactions
- Other ester anaesthetics (procaine, benzocaine)
- Cross-allergy through a common metabolite.
What is monitored
- Response of the eye and cornea
- Signs of allergic reaction
- With spinal use: blood pressure and block level
Administration and safety
- The drops are applied by health staff: they are not given to the patient for home use.
- Do not inject or apply inside the eye.
- Warn the patient not to touch or rub the eye while it is numb.
Nursing care
- Explain that the eye will be numb for a while and must be protected from knocks, dust and rubbing.
- Make sure the patient does not leave with the bottle of drops.
- Watch for intense burning or redness.
Test yourself
Think of the answer, then tap the question to see it.
Why is a tetracaine eye drop not given to the patient for home use?
Prolonged or repeated use can cause permanent corneal opacity and ulceration with vision loss, and the numb eye is easily injured.
Which chemical group does tetracaine belong to, and which enzyme breaks it down?
It is an amino ester; plasma cholinesterase hydrolyses it.
Why can a patient allergic to procaine react to tetracaine?
Both are esters and share a metabolite that causes the cross-allergic reaction.
Related drugs
Related conditions
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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - TETRACAINE HYDROCHLORIDE solution/ drops (DailyMed (U.S. National Library of Medicine), 2026); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 25 (McGraw Hill, 2023); eEML - Electronic Essential Medicines List (World Health Organization, 2025); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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