Xanthines affect primarily the central nervous system, the cardiovascular system and peripheral nerves. There is a diuretic effect as well. So the sign seen with toxicity include hyperexitablility, hyper irritability, increased heart rate, restlessness, increased urination, vomiting and muscular tremors or tenseness. Under some circumstances these signs can lead to secondary problems like hyperthermia. In severe cases, seizures or cardiac arrest can occur.
Death can result from severe intoxication.
There is no specific antidote for this poisoning. Inducing vomiting can help if the ingestion is known and has occurred within one to two hours. Administration of activated charcoal may inhibit absorption of the toxin from the digestive tract. It may be necessary to use medications to control the effects of the poisoning, especially seizure control medications, oxygen therapy, intravenous fluids, and medications to control the effects on the heart. With ingestion of milk chocolate, diarrhea is a common secondary problem.