Eye drops are topical ophthalmic solutions formulated for application directly to the eye’s surface, not for consumption. These medications contain active ingredients designed to work locally on ocular tissue with minimal systemic absorption. Ingesting these solutions bypasses the body’s natural protective barriers, leading to rapid and complete absorption of chemicals into the bloodstream. This formulation is incompatible with systemic circulation, creating a significant poisoning risk when swallowed.
Why Ingestion Poses a Risk
The danger of drinking eye drops stems from the difference between ocular and oral drug delivery. When applied to the eye, the medication is intended for local action, and only a tiny fraction is absorbed systemically. Most liquid drains away through the tear duct system, preventing systemic side effects when used correctly.
Oral ingestion subjects the entire dose to the highly efficient absorption pathway of the digestive tract. Active ingredients are quickly absorbed through the gut lining and enter the circulatory system at high concentrations. This rapid, high-dose delivery overwhelms the body because it largely bypasses the liver.
The liver filters and breaks down toxins through first-pass metabolism. Bypassing this process dramatically increases the drug’s bioavailability, resulting in toxic blood levels significantly higher than those achieved by topical application. Even a small amount can deliver a potent, full-body dose, turning a localized medication into a systemic poison.
Common Toxic Components in Over-the-Counter Eye Drops
The most common danger comes from vasoconstrictor drugs found in many redness-relieving products. These chemicals, such as tetrahydrozoline, naphazoline, and oxymetazoline, are imidazoline derivatives. Their intended action is to constrict small blood vessels on the eye’s surface to temporarily relieve redness.
When ingested, these vasoconstrictors act throughout the entire body’s circulatory and nervous systems, not just locally. Tetrahydrozoline, for instance, is structurally similar to potent medications used to treat high blood pressure. Swallowing the solution causes this powerful constricting action systemically, leading to severe effects on the heart and brain.
Preservative Toxicity
Beyond the active decongestants, certain preservatives can contribute to toxicity. Benzalkonium chloride (BAC) is a preservative widely used in ophthalmic solutions for its antimicrobial properties. While safe in low concentrations, concentrated forms of BAC are corrosive and can cause local injury to the gastrointestinal tract upon ingestion.
Immediate Physiological Effects of Ingestion
Ingestion of vasoconstrictor-containing eye drops primarily targets the central nervous system (CNS) and cardiovascular system, producing severe and rapid symptoms. The systemic effect causes a severe drop in blood pressure (hypotension) and a slow heart rate (bradycardia). These cardiac effects quickly lead to inadequate blood flow to the body’s organs.
CNS depression is a hallmark of this poisoning. The person may experience drowsiness, lethargy, and an altered mental state, potentially progressing to deep sedation or coma. Respiratory depression, characterized by slowed breathing, is a serious outcome that may require emergency airway support.
Children are at a high risk due to their small body weight; a minuscule amount can be toxic. As little as one-half of a teaspoonful of a tetrahydrozoline solution can cause pronounced reactions. Other symptoms include nausea, vomiting, hypothermia, and a change in pupil size. Effects can manifest quickly, often within 30 minutes, demanding immediate medical intervention.
Emergency Response and Seeking Medical Help
If eye drops are ingested, immediate medical attention is necessary, even if symptoms have not yet appeared. The first step is to call a poison control center immediately for expert guidance. In the United States, the national toll-free Poison Help hotline is 1-800-222-1222.
When speaking with the medical professional, provide specific, detailed information to ensure the correct course of action. This includes the product name, active ingredients, an estimate of the amount swallowed, and the time of ingestion.
It is not recommended to induce vomiting, as this can cause more harm, especially with corrosive substances. Only a medical professional or poison control specialist should advise on this measure. The person should be monitored for any changes in consciousness, breathing, or heart rate while waiting for emergency services.