Ketamine (INN) is a medication used mainly for starting and maintaining anesthesia. Other uses include sedation in intensive care, as a pain killer, as treatment of bronchospasm, as a treatment for complex regional pain syndrome and as an antidepressant. It induces a trance like state while providing pain relief, sedation, and memory loss. Heart function, breathing and airway reflexes generally remain functional. Common side effects include a number of psychological reactions as the medication wears. This may include agitation, confusion and psychosis among others. Elevated blood pressure and muscle tremors are relatively common, while low blood pressure and a decrease in breathing is less so. Spasms of the larynx may rarely occur. Pharmacologically, ketamine is classified as an NMDA receptor antagonist, but it also acts at numerous other sites (including opioid receptors and monoamine transporters). Like other drugs in its class, such as phencyclidine (PCP), it is classified as a dissociative agent. Ketamine was first developed in 1962. It is on the WHO Model List of Essential Medicines, a list of essential medicines that should be available in a health system. Its hydrochloride salt is sold as Ketanest, Ketaset, and Ketalar. Its use as a recreational drug has been associated with several high-profile deaths.