The trio that will make your heart race… or drop
Imidazoline decongestants
Written by Van Quach, PharmD, SPI at the Washington Poison Center
Over-the-counter allergy relief eye drops and nasal sprays are perceived as low risk due to their small bottle size (5 mL, 10 mL, and 15 mL) and not needing a prescription to purchase. Let’s give them the spotlight they deserve on how toxic they can be, especially in pediatric populations — young children have developed serious adverse effects after ingesting as little as half a teaspoon of eye drops or nasal spray containing an imidazoline. In addition, adults who intentionally ingest a toxic amount of tetrahydrozoline may experience hallucinations with severe bradycardia and/or hypotension that can last up to 6 days post-ingestion.
Mechanism of action
When ingested, imidazoline decongestants are potent central and peripheral α2-adrenergic and imidazoline receptor agonists. In overdose, they cause CNS depression and initial brief hypertension followed by hypotension, bradycardia, and respiratory depression (similar to α2 agonists like clonidine).
Symptoms
Onset is rapid, within 20 to 60 minutes of oral ingestion. Usually resolves within 24 hours.
Differential Diagnosis
Opioids, muscle relaxants, benzodiazepines, antipsychotics, clonidine, and antidepressants. Don’t forget medical causes such as trauma and intracranial hypertension.
References
1. U.S. Food and Drug Administration: FDA Drug Safety Communication: Serious adverse events from accidental ingestion by children of over-the-counter eye drops and nasal sprays. U.S. Food and Drug Administration. Silver Spring, MD. 2012. Available from URL: http://www.fda.gov/Drugs/DrugSafety/ucm325257.htm#healthcare.
2. Malley C, Westover R, Scanlon M, et al: One lick could kill? Symptomatic tetrahydrozoline exposure after child licks eye-drop container. Clinical Toxicology 2021; 59(11):1178–1179.
3. Heuser W, Pettet D, Silver D, et al: No more red eyes: toxic tetrahydrozoline ingestion in an adult. A case report and literature review. Clinical Toxicology 2019; 57(10):951–953.
4. Spiller H, Rogers J, Sawyer T, et al: Drug facilitated sexual assault using an over-the-counter ocular solution containing tetrahydrozoline (Visine®). Legal Medicine 2007; 2007 Jul;9(4):192–5.
5. Holmes JF & Berman DA: Use of naloxone to reverse symptomatic tetrahydrozoline overdose in a child. Pediatric Emergency Care 1999; 15:193–194.
6. Katar S, Taskesen M, & Okur N: Naloxone use in a newborn with apnea due to tetrahydrozoline intoxication. Pediatrics International 2010; 52(3):488–489.
7. Poisindex
