Neurologic symptoms may persist for several days. May cause gastrointestinal irritation, nausea, vomiting, stimulation of gastric acid secretion, anorexia, hematemesis, abdominal cramps, diarrhea, and diuresis followed by oliguria and dehydration. Other effects may include alternating states of consciousness and muscle twitching, tremors, hyperesthesia, hypertonicity or hypotonicity, trismus, opisthotonus and convulsions. Slight increase in basal metabolic rate, metabolic acidosis, ketonuria, glycosuria, hyperglycemia, hypokalemia and rhabdomyolysis have been reported. Other effects may include dyspnea, tachypnea, chest tightness, palpitations, increase in systolic blood pressure, and arrhythmias including tachycardia and extrasystoles.
Seizures generally precede death.
In addition to the effects detailed in acute exposure, agitation, disturbed sleep, caffeine-induced psychosis, heartburn and hyperventilation may occur. Low grade fever and elevated plasma free fatty acid have been reported. Respiratory failure and cardiopulmonary arrest may occur. Prolonged use of high doses may result in tolerence, physical and psychological dependence. Symptoms of withdrawal may occur following abrupt cessation.