Amyl nitrite is a chemical compound with the formula C5H11ONO. A variety of isomers are known, but they all feature an amyl group attached to the nitrite functional group. The alkyl group is unreactive and the chemical and biological properties are mainly due to the nitrite group. Like other alkyl nitrites, amyl nitrite is bioactive in mammals, being a vasodilator, which is the basis of its use as a prescription medicine. As an inhalant, it also has a psychoactive effect, which has led to its recreational use, with its smell being described as that of old socks or dirty feet. It is also referred to as banapple gas. It was first documented in 1844 and came into medical use in 1867. Uses 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. Amyl nitrite is used as a cleaning agent and solvent in industrial and household applications. It replaced dichlorodifluoromethane, an industrial chemical universally banned in 1996 due to damage to the ozone layer, as a printed circuit board cleaner. Trace amounts are added to some perfumes. It is also used recreationally as an inhalant drug that induces a brief euphoric state, and when combined with other intoxicant stimulant drugs such as cocaine or MDMA, the euphoric state intensifies and is prolonged. Once some stimulative drugs wear off, a common side effect is a period of depression or anxiety, colloquially called a "come down"; amyl nitrite is sometimes used to combat these negative after-effects. This effect, combined with its dissociative effects, has led to its use as a recreational drug (see poppers). Nomenclature The term "amyl nitrite" encompasses several isomers. In older literature, the common non-systematic name amyl was often used for the pentyl group, where the amyl group is a linear or normal (n) alkyl group, and the resulting amyl nitrite would have the structural formula CH3(CH2)4ONO, also referred to as n-amyl nitrite. A common form of amyl nitrite is the isomer with the formula (CH3)2CHCH2CH2ONO, which may be more specifically referred to as isoamyl nitrite. The similarly named amyl nitrate has very different properties. At the same time, isopropyl nitrite has a similar structure and similar uses (also called 'poppers') but with worse side-effects.