ISOPENTYL NITRITE (Amyl nitrite) is a chemical compound with an amyl group attached to the nitrite functional group. Amyl nitrite, in common with other alkyl nitrites, is a potent vasodilator; it expands blood vessels, resulting in lowering of the blood pressure. Alkyl nitrites are a source of nitric oxide, which signals for relaxation of the involuntary muscles. Physical effects include the decrease in blood pressure, headache, flushing of the face, increased heart rate, dizziness, and relaxation of involuntary muscles, especially the blood vessel walls and the internal and external anal sphincter. There are no withdrawal symptoms. Overdose symptoms include nausea, vomiting, hypotension, hypoventilation, shortness of breath, and fainting. The effects set in very quickly, typically within a few seconds and disappear within a few minutes. Amyl nitrite may also intensify the experience of synesthesia. Amyl nitrite is employed medically to treat heart diseases as well as angina. Amyl nitrite is sometimes used as an antidote for cyanide poisoning. It can act as an oxidant, to induce the formation of methemoglobin. Methemoglobin, in turn, can sequester cyanide as cyanomethemoglobin.