Patients who take greater than recommended levels of an antimalarial agent are at risk for acute poisoning that can be fatal. This often manifests as irreversible cardiac arrest within several hours of ingesting excess dosage of the drug. Symptoms may first appear within 30 minutes and include headache, drowsiness, visual changes and seizures. Patients who experience these symptoms should seek immediate medical treatment, which usually includes induced vomiting or flushing the stomach with water, followed by administration of activated charcoal (which prevents poison from being absorbed into the body).