'Ice' is a street name commonly used to refer to methamphetamine (meth-am-FET-a-meen), a stimulant drug that can be smoked like crack cocaine. In the purest form, ice crystals resemble rock salt, rock candy, or ice chips, but a yellowish tint may indicate poor quality or low purity. When smoked, ice produces a powerful, euphoric high that can last up to 15 hours. Like other forms of methamphetamine, ice acts on the brain by producing a rapid and powerful stimulant effect that's characterized by extreme alertness, increased energy, nervous excitement, irritability, and extended wakefulness. Noticeable physical effects include rapid heart rate, increased respiration, an elevation in blood pressure, dilated pupils, and a decrease in appetite. It's not unusual for even the casual user to experience dry mouth, dizziness, sweating, headache, blurred vision, mild tremors, sleeplessness, and anxiety. At higher doses, users run an increased risk of physical collapse, stroke, and heart failure. Tolerance to ice builds rapidly, and users require increasingly more of the drug to produce the desired effect. Without being aware of what's taking place, it's easy for the casual methamphetamine user to quickly become dependent. For more information about ice, consult a local health care professional.