RiteMED Clonidine Overdosage

In a patient who ingested 100 mg clonidine, plasma levels were 60 ng/mL (1 hour), 190 ng/mL (1.5 hours), 370 ng/mL (2 hours) and 120 ng/mL (5.5 and 6.5 hours). The patient developed hypertension followed by hypotension, bradycardia, apnea, hallucinations, semicoma, and premature ventricular contractions. The patient fully recovered after intensive treatment.
Symptoms of clonidine overdosage are hypotension (which may be profound), transient hypertension, bradycardia, weakness, vomiting, irritability, diminished or absent reflexes, lethargy, somnolence, drowsiness, deep sedation, skin pallor, hypothermia, decreased or irregular heart rate, dryness of the mouth, constricted pupils with poor reaction to light, respiratory depression, hypoventilation, miosis, reversible cardiac conduction defects or dysrhythmias, apnea, coma, and seizures.
Induction of emesis is usually not recommended because of rapid onset of CNS depression. Establish respiration if necessary, perform gastric lavage and administer activated charcoal. A saline cathartic (magnesium sulfate) will increase the rate of transport through the gastrointestinal tract. Routine hemodialysis is of limited benefit because a maximum of 5% of circulating clonidine is removed.
Supportive care may include atropine sulfate for the treatment of persistent bradycardia, and dopamine infusion and IV fluids for hypotension.
Hypertension can be treated with IV furosemide or diazoxide or α-blocking agents such as phentolamine. Tolazoline, an alpha-blocker, in IV doses of 10 mg at 30 minute intervals may reverse clonidine's effects if other efforts fail. Naloxone may be a useful adjunct for the management of clonidine-induced respiratory depression, hypotension or coma.