OVERDOSE
Clonidine Hydrochloride: The signs and symptoms of clonidine
hydrochloride ovedosage include hypotension, bradycardia,
lethargy, irritability, weakness, somnolence, diminished
or absent reflexes, miosis, vomiting and hypoventilation.
With large overdoses, reversible cardiac conduction defects
or arrhythmias, apnea, seizures and transient hypertension
have been reported. The oral LD 50 of clonidine in rats
was 465 mg/kg, and in mice 206 mg/kg.
The general treatment of clonidine hydrochloride overdosage
may include intravenous fluids as indicated. Bradycardia
can be treated with intravenous atropine sulfate and hypotension
with dopamine infusion in addition to intravenous fluids.
Hypertension, associated with overdosage, has been treated
with intravenous furosemide or diazoxide or alpha-blocking
agents such as phentolamine. Tolazoline, an alpha-blocker,
in intravenous doses of 10 mg at 30-minute intervals,
may reverse clonidine's effects if other efforts fail.
Routine hemodialysis is of limited benefit, since a maximum
of 5% of circulating clonidine is removed.
In a patient who ingested 100 mg clonidine hydrochloride,
plasma clonidine levels were 60 ng/mL (one hour), 190
ng/mL (1.5 hours), 370 ng/mL (two hours) and 120 ng/mL
(5.5 and 6.5 hours). This patient developed hypertension
followed by hypotension, bradycardia, apnea, hallucinations,
semicoma, and premature ventricular contractions. The
patient fully recovered after intensive treatment.
Chlorthalidone: Symptoms of acute overdosage
include nausea, weakness, dizziness and disturbances of
electrolyte balance. The oral LD 50 of the
drug in the mouse and the rat is more than 25,000 mg/kg
body weight. The minimum lethal dose (MLD) in humans has
not been established. There is no specific antidote but
gastric lavage is recommended, followed by supportive
treatment. Where necessary, this may include intravenous
dextrose-saline with potassium, administered with caution.
CONTRAINDICATIONS
Anuria: CLORPRES™ is contraindicated in patients
with known hypersensitivity to chlorthalidone or other
sulfonamide-derived drugs.
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