Ketamine was introduced to clinical use in 1970 as an intravenous anaesthetic but had a broad spectrum of pharmacological actions. It can, in fact, induce sedation, catalepsy, somatic analgesia, bronchodilation, and even stimulation of the sympathetic nervous system. Although it is accompanied by a bad reputation as a substance of abuse on the one hand and as a “vet medicine” on the other, its use in anaesthesia is growing, so are its fields of application.
Chemically, it is a water-soluble derivative of phencyclidine. The molecule contains an asymmetric carbon atom with two enantiomers: the S (+) and R (-) isomers. Redistribution to peripheral tissues is rapid. Metabolization is hepatic and follows the pathways of N-demethylation and hydroxylation. The main metabolite, norketamine, preserves 1/5 – 1/3 of the anaesthetic power of the starting molecule. It is excreted as norketamine or in the form of hydroxylated metabolites, both at the urinary and faecal level.
The main mechanism of action is a non-competitive antagonism with the N-methyl-D-aspartate (NMDA) receptor.
The drug induces stimulation of the cardiovascular system, which leads to an increased heart rate and blood pressure.
It also increases saliva flow and muscle tone. The effects on the respiratory system are minor and consist mainly in the relaxation of the bronchial musculature.
At the level of the central nervous system, it can induce catalepsy (a state of akinesia with loss of orthostatic reflexes but not of consciousness), amnesia, and dose-dependent anesthetic effect. In addition, the dissociative state keeps the patient apparently awake but detached from the surrounding environment.
As anticipated, the possibilities of application of the drug are growing. In the dental field, for example, it is proposed to be used in methods of procedural sedation, also through intranasal administration and, above all, in the paediatric patient.
In order to validate its clinical use, it is certainly desirable to implement the clinical evidence available. At the moment, one of the most investigated aspects of the dental use of the drug is represented by the control of acute postoperative pain, of which the surgery of the third molar is an optimal model.
In 2014, Surendar and colleagues published in the Journal of Clinical Pediatric Dentistry a study involving a total of 134 patients undergoing procedural anesthesia during the extraction of the third molar. The survey showed that a sub-anesthetic dose of ketamine could not reduce postoperative pain or reduce the use of analgesic drugs. These indications, without contraindicating the use of the drug, underline the need to gain knowledge in the field of new clinical uses, such as dentistry.