indication

For use as the sole anesthetic agent for diagnostic and surgical procedures that do not require skeletal muscle relaxation.

pharmacology

Ketamine is a rapid-acting general anesthetic producing an anesthetic state characterized by profound analgesia, normal pharyngeal-laryngeal reflexes, normal or slightly enhanced skeletal muscle tone, cardiovascular and respiratory stimulation, and occasionally a transient and minimal respiratory depression. Ketamine is indicated as the sole anesthetic agent for diagnostic and surgical procedures that do not require skeletal muscle relaxation. The anesthetic state produced by Ketamine has been termed “dissociative anesthesia” in that it appears to selectively interrupt association pathways of the brain before producing somesthetic sensory blockade. It may selectively depress the thalamoneocortical system before significantly obtunding the more ancient cerebral centers and pathways (reticularactivating and limbic systems).

mechanism of action

Ketamine has several clinically useful properties, including analgesia and less cardiorespiratory depressant effects than other anaesthetic agents, it also causes some stimulation of the cardiocascular system. Ketamine has been reported to produce general as well as local anaesthesia. It interacts with N-methyl-D-aspartate (NMDA) receptors, opioid receptors, monoaminergic receptors, muscarinic receptors and voltage sensitive Ca ion channels. Unlike other general anaesthetic agents, ketamine does not interact with GABA receptors.

biotransformation

Hepatic.

absorption

Rapidly absorbed following parenteral administration.

half life

2.5-3 hours.

drug interactions

Memantine: Increased risk of CNS adverse effects with this association

Telithromycin: Telithromycin may reduce clearance of Ketamine. Consider alternate therapy or monitor for changes in the therapeutic/adverse effects of Ketamine if Telithromycin is initiated, discontinued or dose changed.

Thiotepa: Thiotepa, a strong CYP2B6 inhibitor, may decrease the metabolism and clearance of Ketamine, a CYP2B6 substrate. Consider alternate therapy or monitor for changes in the therapeutic and adverse effects of Ketamine if Thiotepa is initiated, discontinued or dose changed.

Tolbutamide: Tolbutamide, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Ketamine. Consider alternate therapy or monitor for changes in Ketamine therapeutic and adverse effects if Tolbutamide is initiated, discontinued or dose changed.

Voriconazole: Voriconazole, a strong CYP3A4 inhibitor, may increase the serum concentration of ketamine by decreasing its metabolism. Monitor for changes in the therapeutic and adverse effects of ketamine if voriconazole is initiated, discontinued or dose changed.