Is Ketamine an Opioid?

Ketamine has been shown to be a potent, fast-acting antidepressant for people with treatment-resistant depression. A recent study has shown that when Ketamine is co-administered with Naltrexone, the antidepressant effect is attenuated. Naltrexone is an opioid receptor antagonist, blocking the effect of opiates. It is typically used to help with opiate and alcohol addiction. This means that the antidepressant effects of ketamine rely upon activation of opioid receptors.

Interestingly, people receiving both ketamine and naltrexone still experience the classic dissociative effects and perceptual changes caused by ketamine. This shows that  the dissociative effects alone are not enough to create the antidepressant effects. Does this mean ketamine is an opioid? If so, what does this mean? Read the full text here and a brief commentary here.


Long-term Antidepressant Effect of Repeated Ketamine Administration

Long-term Antidepressant Effect of
Repeated Ketamine Administration

Although ketamine has a fast-acting antidepressant effect, it typically only lasts for about a week before depressive symptoms re-emerge. Furthermore, it is typically administered via intravenous infusion, which requires the person be in a medical setting.
In this study, it was found ketamine had a rapid-acting antidpressant effect when administered intranasally. Furthermore, these effects were maintained for 8 weeks with repeated administrations, beginnning at twice per week, and decreasing to once per week. This is the first trial showing the potential to use ketamine as a long-term antidepressant.

Read the full text here.

The Entropic Brain Theory of Consciousness

In 2014 Robin Carhart-Harris, of the Imperial College London, published a paper outlining the Entropic Brain Theory of consciousness, which helps explain how the psychedelic state occurs in reference to other states of consciousness. A new paper has now been published in the journal of Neuropharmacology, outlining more recent evidence which can be used to further solidify the parameters of the entropic brain theory,

Basically, the in normal waking consciousness, we have developed filters on our perception, which constrain the way in which we see the world. These filters are products of the patterns we have viewed to reoccur in the world. Such filters reduce the amount of energy we expend in navigating the world.

Without these filters on our perception, there would be no consciousness. We would simply be seeing the world as completely interconnected and without boundaries… Sound familiar?

Carhart-harris hypothesizes that psychedelics help reduce the filters on our perception, opening us up to new ways of viewing the world. The consequence of this is that the amount of energy used and disorder in our perception is increased (i.e. entropy is increased), making this state less sustainable for long periods of time. However, transiently reducing these filters may serve to help us move on from our current dysfunctional ways of thinking, such as in the depressed mind.