Ketamine was first created in 1962 to be used as an anesthetic. Ketamine is perhaps the most widely used agent in the world with regards to its use as an anesthetic in children and adults. Ketamine has unique safety features that make it different than any other anesthetics. Specifically, it does not suppress the gag reflex and it does not depress the respiratory system. When used as an anesthetic, no additional breathing apparatus is needed. In addition, when delivery of the medication has stopped, the effects of ketamine are very short lived and on the order of minutes as opposed to hours or days.
Ketamine has a very large “safety window.” The entire dose of ketamine used during typical surgical anesthesia is approximately 3% of that which would be considered a lethal dose. The dose used for the treatment of depression is a mere 1/10th of 1% of the lethal dose, meaning that there is essentially a zero chance of an overdose. The low dose used during ketamine infusions for depression creates transient cognitive impairment with distorted perceptions and sedation that quickly resolves once the infusion is over.
The wide safety margin of ketamine make it an ideal medication to use as an anesthetic on the battlefield, or in less developed countries, where sophisticated oversight of the surgical process is not as readily accessible. In fact, the World Health Organization lists ketamine as one of its core medicines on the “Essential Drug List.” The American Red Cross uses ketamine as part of its standard protocol when anesthetics are used in emergent situations.
Nowhere are medications more scrutinized than when they are used with children. There is a study in which 11,000 cases involving children receiving ketamine for sedation and surgical purposes were reviewed for safety concerns. The study found that it was well tolerated, there were no negative lasting effects, and that it was safe to use. (Green, Ann Emerg Med 1990). Those that receive ketamine as an anesthetic receive it for a longer duration and at much higher doses than those who receive it for the treatment of depression.
In short, when used in the clinical setting under the supervision of a medical professional, the delivery of low dose ketamine infusions for the treatment of depression is safe.