Ketamine

Summary & key facts

This chapter reviews what ketamine does in the body and how it is used in medicine. Ketamine comes in two mirror-image forms, and the S(+) form is about three to four times more powerful as an anesthetic. It works on several brain and nerve receptors, is easy to give by different routes because it dissolves in water and fat, and is broken down by liver enzymes. Doctors use it for 'dissociative' anesthesia, for pain relief after surgery, and for some kinds of chronic pain. It also widens airways and raises heart and blood pressure, which makes it useful for injured patients and people in shock. The drug can cause strange psychological effects, and those side-effects limit how widely it is used.

Key facts:

• Ketamine exists as two isomers called S(+) and R(-); the S(+) isomer is about three to four times more potent as an anesthetic than the R(-) isomer.
• Ketamine works on several kinds of receptors in the brain and nerves, including NMDA receptors (which are involved in how nerve cells communicate), opioid receptors, muscarinic receptors, and some voltage-gated channels.
• Because ketamine dissolves in both water and fat, it can be given in several ways and spreads widely through the body.
• The liver breaks ketamine down using common liver enzymes.
• Ketamine causes bronchodilation, which means it helps open the airways, and it stimulates the sympathetic nervous system, which raises heart rate and blood pressure.
• Clinically, ketamine is used for premedication, sedation, and to start and maintain general anesthesia that is described as dissociative anesthesia.
• Even at doses too low to cause full anesthesia, ketamine reduces pain, so it is used for post-operative pain relief and as a treatment option in chronic pain.
• Combining ketamine with sedatives such as midazolam or propofol can be helpful and is considered safe for sedation and pain control in intensive care, especially in sepsis or when blood pressure is unstable.
• Psycho-mimetic side effects — meaning odd or disturbing changes in perception and thinking — are common and are an important reason ketamine use can be limited.

Topics

Anesthesia and Neurotoxicity Research Anesthesia and Sedative Agents Treatment of Major Depression

Categories

Anesthesiology and Pain Medicine Health Sciences Medicine

Tags

Analgesic Anesthesia Dissociative Internal medicine Ketamine Medicine Midazolam NMDA receptor Pharmacology Receptor Sedation

Substances

Ketamine

Conditions & symptoms

Chronic Pain Chronic pain