Stimulants are psychoactive substances that cause an increase in activity in various parts of the central nervous system or directly increase muscle activity and are often referred to as “uppers”. Therapeutically, stimulants have also been used for the treatment of obesity, asthma and other respiratory problems. Amphetamine, dextroamphetamine and methamphetamine are collectively referred to as amphetamines. Cocaine is a stimulant but is not normally prescribed therapeutically for its stimulant properties, although it sees clinical use as a local anesthetic, particularly in ophthalmology. There are three forms of cocaine: cocaine hydrochloride, freebase and crack cocaine. Cocaine users are polydrug users, often consuming cocaine with alcohol and tobacco, with other illicit drugs such as other stimulants and cannabis, or with heroin. Cocaine withdrawal generally occurs in three phases: the “crash”, the “withdrawal” and the “extinction”. Khat (also spelled Quat, Qat and Kat) acts as a social lubricant in mostly Muslim countries, with links to (especially) Yemen, Ethiopia or Somalia. Synthetic cathinones, more commonly known as “bath salts”, are synthetic drugs chemically related to cathinone, one of the principal psychoactive components in khat.