Source: Good Day Pharmacy, Poudre Valley Hospital and,Children’s Hospital Colorado. This is one way of what a Clonidine overdose can look like, agitation and hallucinations, and extreme pain. Here are the rest, large overdoses may result in reversible cardiac conduction defects or dysrhythmias, apnea, coma and seizures. Signs and symptoms of overdose generally occur within 30 minutes to two hours after exposure. As little as 0.1 mg of clonidine has produced signs of toxicity in children.