Ketamine
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This is how ketamine works
Consciousness is controlled by the interaction of many different messenger substances (such as glutamate, GABA or acetylcholine) in the central nervous system (brain and spinal cord). In the case of painful or stressful interventions, this awareness must be switched off. At the same time, in addition to pain relief, muscle relaxation and the cancellation of memories are required during operations.
The ketamine effect is based on the blockade of the docking point of the messenger substance glutamate (so-called NMDA receptor), whereby consciousness can be reversibly switched off. Ketamine is the only so-called "injection anesthetic" that also has an analgesic effect.
Uptake, breakdown and excretion of ketamine
The active substance must be injected into a vein or muscle. The effect occurs after intravenous administration already after 30 seconds, with intramuscular administration after five to ten minutes. The mind-numbing effect lasts for about a quarter of an hour, but the sensation of pain is suppressed for at least 30 minutes. After the active ingredient has been distributed throughout the body, it is broken down in the liver. The breakdown products are mainly excreted through the kidneys.
When is ketamine used?
The active ingredient ketamine is used in certain special cases:
- Treatment of pain in emergency medicine
- Anesthesia for patients with low blood pressure
This is how ketamine is used
The active ingredient is used exclusively by specialist staff. The ketamine dosage for pain relief is 0.25 to one milligram per kilogram of body weight. For induction of anesthesia, one to two milligrams per kilogram of body weight are required for intravenous administration, and four to six milligrams per kilogram of body weight for intramuscular administration.
A useful combination results with the active ingredient midazolam. The representative from the group of so-called benzodiazepines reduces the side effects of ketamine (hallucinations, nightmares when waking up from anesthesia).
What are the side effects of ketamine?
The active ingredient ketamine causes dreams and hallucinations in ten to 30 percent of those treated. Furthermore, there is often an increase in blood pressure, heart rate and salivation.
What should be considered when taking ketamine?
In the case of cardiovascular problems, severe psychological problems, increased intraocular pressure and increased intracranial pressure, ketamine should only be used after a strict medical benefit-risk assessment.
Contraindications
The active ingredient must not be used in patients with high blood pressure or hyperthyroidism.
So-called xanthine derivatives such as theophylline (for asthma) must not be combined with ketamine, as this can lead to seizures.
Interactions
When other drugs are used at the same time, interactions can occur.
Thyroid hormones and so-called sympathomimetics such as adrenaline (during resuscitation), xylometazoline (in decongestant nasal sprays) or fenoterol (asthma medicine) can increase the side effects of ketamine (increase in blood pressure).
Driving and using machines
After anesthesia with ketamine, patients should not actively drive or operate heavy machinery for at least 24 hours, as the active ingredient can severely impair their ability to react. After an outpatient operation, you should only go home with a companion.
Age restrictions
Ketamine may also be used in pediatric surgery. Here, however, the additional administration of sleeping pills (benzodiazepines such as midazolam) is dispensed with.
pregnancy and breast feeding period
There are so far insufficient data on the use of ketamine in pregnant women. Before use, the doctor will therefore weigh the individual benefit against the existing risk.
The active ingredient passes into breast milk. In order not to harm the baby, breastfeeding should be stopped after the use of ketamine or at least paused until no significant amount of active ingredient can be detected in the breast milk.
How To Get Ketamine Medicines
Medicines containing ketamine require a prescription and are usually not available from pharmacies for private individuals. The active ingredient may only be used by qualified personnel for induction of anesthesia.
Since when has ketamine been known?
Ketamine was first made by chemist Stevens in 1962. It was first used on humans three years later. The active ingredient has been approved in Germany since 1969.
More interesting facts about ketamine
The active ingredient ketamine is practically no longer used in “normal” anesthesia. However, it is a popular active ingredient in the treatment of pain in disaster medicine. Due to its special properties such as circulatory stabilization and expansion of the pulmonary vessels, it is particularly suitable for such emergencies. Ketamine must then always be combined with strong sedatives (midazolam), as otherwise a nightmare-like wake-up after anesthesia and hallucinations can occur.
After the anesthesia, the patient is often still in a twilight state, which is due to the mechanism of so-called "dissociative anesthesia". The effect decreases slowly and evenly. However, this “side effect” makes the active ingredient a good pain reliever in disaster medicine: after administration, ketamine causes strong calming (sedation) for a relatively long period of time.
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