Isoamyl nitrite is a chemical substance and also an emergency drug, mainly used clinically to prevent acute attacks of angina pectoris and detoxification of cyanide poisoning. Isoamyl nitrite has a strong vasodilating effect and can be inhaled through the nostrils during an angina attack to rapidly dilate blood vessels and relieve angina symptoms, but it can easily cause a drop in blood pressure and is less commonly used in clinical practice. When cyanide poisoning, isoamyl nitrite can oxidize iron in hemoglobin into methemoglobin, which can combine cyanide ions into non-toxic cyanide methemoglobin.