Abstract
Tetrahydrozoline is an imidazoline derivative with alpha receptor agonist activity widely available in over-the-counter topical ocular and nasal formulations. More than 1,600 cases of oral exposures are reported to United States poison centers annually (CitationCitation). Reports of significant toxicity from tetrahydrozoline ingestion are unusual but have occured primarily in small children after unintentional ingestion (Citation). We report a case of unintentional tetrahydrozoline ingestion with cardiovascular effects persisting for 36 hours.
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A 17-year-old, 74 kg woman ingested a “mouthful” from a 12-ounce bottle of 0.05% tetrahydrozoline ocular formulation. The patient had a mild upper respiratory tract infection and mistakenly believed the bottle contained a generic cough/cold remedy. She reported the amount ingested as about 10 to 15 mL. Medical history included chest palpitations and metoprolol 25 mg extended-release formulation taken once a day (last dose 22 hours earlier).
Upon arrival at the emergency department (ED) 25 minutes post-ingestion, the patient was lethargic but oriented, with slowed speech and ataxia. She complained of dizziness, a headache, and sinus congestion. Vital signs were temperature 97.5°F, pulse 39 beats/minute, respiratory rate 16 breaths/minute, and BP 153/90 mmHg; pulse oximeter 98%. Examination revealed pupils 6 mm and a moist oropharynx but was otherwise unremarkable. The family brought in the bottle of generic tetrahydrozoline solution, which on visual inspection appeared to have less than one ounce missing. The patient was admitted for observation and received an intravenous infusion of 100 mL/hr of 0.9% NaCl solution. No other interventions were performed. A 12-lead electrocardiogram was not performed but a rhythm strip showed sinus bradycardia with a rate of 45 beats/minute; no other dysrhythmias were noted during continuous cardiac monitoring. The results of routine chemistry and hematology tests were unremarkable except for blood glucose of 174 mg/dL and WBC 17,800. A qualitative urine drug screen was negative for cocaine, tetrahydrocannabinol, amphetamines, barbiturates, benzodiazepines, opiates, methadone, and phencyclidine. Over the following 36 hours the patient continued to experience drowsiness, bradycardia, and orthostatic hypotension (). She was discharged to home 38 hours post-ingestion and lost to follow-up. Orders were provided for restarting metoprolol 25 mg once daily the evening following discharge (48 hours post-ingestion).
Table 1. Timeline of clinical effect from tetrahydrozoline ingestion
Absorption of tetrahydrozoline, with systemic adverse effects, can occur from both the nasal mucosa and gastrointestinal tract after intranasal administration (Citation7,Citation8). Clinical reports suggest that tetrahydrozoline shares pre-synaptic alpha2-receptor agonist effects of the other imidazolines (Citation3–6). Clinical effects from ingestion of tetrahydrozoline have included drowsiness, coma, respiratory depression, bradycardia, hypotension, hypotonia, muscle flaccidity and hypothermia (Citation3–6,Citation9–11). In our patient there was an initial hypertension and bradycardia, followed by a persistent orthostatic hypotension. There was also early and persistent CNS depression. The adverse effects from tetrahydrozoline may include persistent cardiovascular effects, including hypotension and bradycardia, for 36 hours. It is unclear if the persistent headache reported by our patient was related to the tetrahydrozoline or the existing sinus congestion, as headache has not been reported previously. Additionally, our patient had a history of chest palpitations, but no arrhythmias or palpitations were reported during her 36 hour ICU stay.
Ingestion in our patient was estimated to be 67 to 102 mcg/kg of tetrahydrozoline, equivalent to a 2 to 3 mL ingestion of the standard over-the-counter 0.05% concentration in a 16 Kg child. This is consistent with previous reports of significant toxicity with similar amounts. (Citation3–5,Citation12).
In summary we report a case of persistent cardiovascular and neurological effects, lasting up to 36 hours after unintentional ingestion of a 0.05% tetrahydrozoline ocular solution.
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