Ketamine is a drug commonly used on both humans and animals for anesthesia, pain relief, also known as analgesia, and treatment of respiratory ailments that interfere with breathing. It is also being studied for use in psychiatric treatments. Some people take it recreationally for its mind-altering effects, though its sale for this purpose is widely outlawed. Ketamine's chemical formula is C13H16ClNO. It can enter the body intravenously, as is usually done for medical use, or by being smoked, inhaled, or swallowed.
Ketamine is an NMDA receptor antagonist, which means that it affects the nervous system by interfering with the normal functioning of molecules called N-methyl D-aspartate receptors (NMDAR). NMDAR molecules in cells are receptors for the excitatory neurotransmitter glutamate, which is important to the transmission of nerve impulses and thus to a person's ability to perceive sensory data such as pain signals. In large amounts, it will also bind to opioid receptors, causing additional analgesic effects. Some research also indicates that the drug encourages a sleep-like state by inhibiting potassium/sodium hyperpolarization-activated cyclic nucleotide-gated channel 1, also called HCN1, a protein involved in the regulation of electric current in the nervous system.
Ketamine's most common use is as an intravenous general anesthetic during medical procedures. Due to its potential hallucinogenic effects, it is frequently used as a supplement to an inhaled anesthetic rather than on its own. Unlike most anesthetics, it usually causes the patient's heart rate and blood pressure to rise to rather than fall. This makes it useful for treating patients who may have lost large amounts of fluid, such as trauma victims. It can also be administered in the form of a fluid or cream as a local anesthetic.
It is also used as an intravenous analgesic for pain relief. Similarly to its use as an anesthetic, ketamine is usually not used alone due its hallucinogenic effects. Instead, small amounts of it are combined with opioids. Analgesics and local anesthetics containing ketamine are especially effective for pain caused by cancer and damage to the nervous system. In addition to its use in humans, the drug is also frequently used by veterinarians as an analgesic or anesthetic for animals.
Ketamine has other medically useful effects. It is used to treat bronchospasms, muscle constrictions in the respiratory system that interfere with breathing. Bronchospasms are common among sufferers of conditions such as asthma, anaphylaxis, and chronic bronchitis, and in severe cases are potentially fatal. It is also an effective treatment for depression in some patients and can cause significant improvements in depression sufferers who are resistant to other antidepressants. It is also being researched as a possible treatment for withdrawal symptoms among recovering opiate addicts.
Ketamine is also used as a recreational drug though this is widely outlawed and potentially hazardous. For this purpose, it is usually smoked or inhaled in the form of a powder. It can cause intense hallucinations and an alteration of consciousness called a dissociative state, in which the user's perceptions of both the outside world and his or her own body and identity seems distant, dreamlike, or unreal. Due to the importance of glutamate in learning and memory formation, the user's memory of the experience once it is over is often fragmentary or missing entirely. Heavy use can affect the brain's physiology and cause memory impairments, and some research suggests that lower levels of use can interfere with the development of dendrites in nerve cells if continued for an extended period of time.