Adrenoceptor agonist poisoning after accidental oral ingestion of brimonidine eye drops

OBJECTIVE: Brimonidine tartrate is a relatively selective alpha(2) adrenic agonist that lowers elevated intraocular pressure. A 2-yr-old boy presented with severe cardiorespiratory symptoms of systemic alpha(2) adrenergic intoxication after accidentally ingesting 2 mL of brimonidine ophthalmic solution (0.2%) orally. At 20 mins after ingestion, he became acutely pale and lethargic, with shallow infrequent respirations. The symptoms resolved completely within the next 10 hrs. METHODS: The pharmacokinetics of brimonidine in plasma and urine were analyzed using gas chromatography and mass spectrometry. RESULTS: Maximum plasma concentrations were 40 ng/mL 5 hrs after ingestion. The plasma elimination half-life value was 2.7 hrs. Elimination via urine was calculated as having a terminal half-life value of 3.2 hrs. CONCLUSIONS: This case illustrates the ability of brimonidine to gain rapid access to the central nervous system. This first passage is followed by a redistribution phase with rising plasma concentrations. Children who accidentally ingest brimonidine orally should be admitted to a pediatric intensive care unit.