Tetracaine is a potent local anesthetic of the ester-linkage type, commonly used in various medical procedures to numb a specific area of the body. It is available in different formulations, including ophthalmic drops for eye procedures, topical solutions or gels for skin numbing, and injections for spinal anesthesia. The potential side effects can differ depending on the route of administration, and most are related to localized reactions. However, serious adverse events can occur with excessive dosage, improper application, or accidental absorption into the bloodstream. Therefore, it is essential for both medical professionals and patients to be aware of the full spectrum of potential reactions associated with this medication.
Common Local Side Effects
Common side effects are typically confined to the site of application and are generally mild and temporary. They are often expected and usually do not require medical intervention.
Topical Application
For tetracaine applied to the skin, common reactions may include:
- Mild stinging, burning, or itching where the medicine was applied.
- Redness or swelling of the treated skin.
- Skin tenderness or mild pain.
- Numbness or tingling in areas of accidental exposure.
Ophthalmic Application
When used as eye drops, tetracaine can cause the following common, but transient, side effects:
- Temporary stinging or burning sensation in the eye upon instillation.
- Conjunctival redness.
- Eye irritation or discomfort.
- Increased sensitivity to light.
- Tearing.
Serious Systemic Adverse Effects
More serious side effects can occur if tetracaine is absorbed systemically into the bloodstream, which is more likely with high doses, large application areas, or application to broken skin. The most feared systemic reaction is Local Anesthetic Systemic Toxicity (LAST) syndrome, which affects the central nervous system (CNS) and cardiovascular system.
Central Nervous System (CNS) Effects
- Dizziness or lightheadedness.
- Confusion or nervousness.
- Blurred vision or ringing in the ears (tinnitus).
- Drowsiness or unusual tiredness.
- Tremors or seizures.
- Slurred speech.
Cardiovascular Effects
- Fast, slow, or irregular heartbeat.
- Changes in blood pressure, typically a drop (hypotension).
- Fainting.
- Chest pain or pressure.
Methemoglobinemia
Methemoglobinemia is a rare but potentially fatal side effect where the blood's oxygen-carrying capacity is reduced. It is a particular risk for infants under six months and individuals with certain genetic conditions. Signs and symptoms include:
- Pale, gray, or blue-colored skin, lips, or fingernails.
- Headache.
- Shortness of breath.
- Unusual fatigue or weakness.
Allergic Reactions
Although rare, severe allergic reactions can occur, with signs including:
- Hives and a generalized skin rash.
- Swelling of the face, lips, tongue, or throat (angioedema).
- Difficulty breathing or wheezing.
- Severe itching.
How Tetracaine Side Effects Vary by Administration Route
| Feature | Topical Application | Ophthalmic Application |
|---|---|---|
| Purpose | Anesthetize the skin surface for minor procedures (e.g., injections, laser treatment). | Anesthetize the eye for short exams and procedures (e.g., pressure testing). |
| Common Side Effects | Mild stinging, burning, itching, skin redness, swelling, oozing, blistering. | Temporary stinging, burning, eye redness, eye irritation, increased tearing, light sensitivity. |
| Serious Local Risks | Infection, severe irritation, or blistering if applied incorrectly or to broken skin. | Prolonged or repeated use can cause corneal epithelial toxicity and permanent corneal damage. |
