According to the Motley Fool, the pharmaceutical company Alkermes has a potential blockbuster drug for treating major depression in its pipeline. Currently in Phase 3 clinical trials, ALKS-5461 is one step away from Alkermes filing for approval by the FDA. Mental Health Daily reported that ALKS-5461 was given fast track approval by the FDA and is expected to be available in 2016. Its projected use is as a supplementary treatment to current antidepressant drugs. But once approved, the “supplementary” element will likely stop because it’s new and fast acting. The problem is, the drug in ALKS-5461 that is supposed to treat depression is an opioid with addictive potential.
Before going further on this issue, we need to take a short trip into pharmacology and neurotransmitter function in order to understand what’s going on. There are proteins embedded within the membrane of a cell called receptors. These receptors receive chemical signals from outside the cell, and in turn produce a biochemical reaction inside the cell. The chemicals that bind and activate a specific receptor are called agonists. While an agonist causes a reaction, an antagonist blocks that reaction from occurring within the cell. It turns the cell off from the influence of the agonist.
Receptors are activated by either endogenous agonists (hormones or neurotransmitters), or exogenous agonists (drugs). Endogenous agonists are produced by the body. The endogenous opioid agonists include dynorphins, and the more widely known endorphins. If you want more information on biochemistry and neurotransmitter activity, try these Wikipedia pages for starters: opioid receptor, mu-opioid receptor, and agonist.
Opioids are known to have energizing and mood enhancing effects with some users. This effect seems to be associated with dynorphin, which is elevated in depression. Dynorphin is a full agonist for the kappa opioid receptor (KOR). Studies like that done by Knoll and Carlezon, “Dynorphin, Stress and Depression,” suggest that KOR antagonists may have a potential therapeutic potential in treating anxiety and depression. While this biochemical hypothesis makes sense to psychiatrist Daniel Carlat, in The Carlat Psychiatry Report, he was more reserved on the treatment potential of ALKS-5461 than Mental Health Daily and the Motley Fool.
The efficacy of ALKS-5461 for depression remains to be seen. Some trials of ALKS-33 alone have already been performed, particularly in the areas of alcohol dependence and binge-eating disorder. These have been negative.
Now let’s look at my concern with ALKS-5461. First, it is a combination of buprenorphine, and samidorphan, or ALKS-33. Buprenorphine is used in addiction treatment as a detoxification drug and in opioid maintenance therapy, where its brand names are Suboxone (buprenorphine with naloxone) and Subutex (buprenorphine without naloxone). Suboxone and Subutex are classified as Schedule III controlled substances, meaning they have a moderate to low potential for physical and psychological withdrawal. Other Schedule III drugs include ketamine and anabolic steroids.
Buprenorphine is a partial mu opioid agonist, meaning it displaces morphine, methadone, and other full opioid agonists from activating the mu opioid receptor (MOR). But it does not provide the same degree of receptor activation as the full agonists (It doesn’t get you as high), resulting in a net decrease of agonist effect and the onset of withdrawal if it used soon after a full agonist like heroin. Patients planning to begin Suboxone maintenance therapy are told to abstain from opioids for twenty-four hours before their first dose of Suboxone.
At lower doses and with individuals who are not dependent on opioids, both full agonists like heroin and partial agonists like buprenorphine will produce identical euphoric effects. Partial agonists like buprenorphine also have a ceiling effect, meaning that past a certain point, typically 12 to 16 mg, no difference in analgesia, euphoria and respiratory depression will be felt.
Buprenorphine does produce physical dependence. Reportedly, this is to a lesser degree than full opioid agonists; and it is supposed to be easier to discontinue at the end of medication treatment. While this is the received wisdom on websites like NAABT, The National Alliance of Advocates for Buprenorphine Treatment, that has not been the case for what I’ve observed clinically with individuals who have tried buprenorphine. Generally I’ve heard that buprenorphine is harder to kick than heroin. So ALKS-5461 will be treating depression with a drug that may be harder to kick than heroin.
Buprenorphine is also a full antagonist of the kappa opioid receptor (KOR), which underlies its use in ALKS-5461 as an antidepressant. If the production of dynorphine by KOR receptors increases with depression, theoretically then buprenorphine would block these receptors and limit the release of dynorphine—elevating the individual’s mood. Peter Tenore, in “Psychotherapeutic Benefits of Opioid Agonist Therapy,” said that opioids like buprenorphine could be “effective, durable and rapid therapeutic agents for anxiety and depression.” The problem is with the partial agonist effect that buprenorphine has on mu opioid receptors (MOR) you can still use buprenorphine to get high.
That was the rationale for combining naloxone with buprenorphine in Suboxone. Naloxone is an opioid antagonist that counters the effects of opioids at the mu receptor, but doesn’t trigger a euphoric effect. Marketed under the brand name of Narcan, naloxone is used to counter the effects of opioids in overdose situations. The death of Phillip Seymour Hoffman led to calls for greater availability of naloxone (see “The Opioid-Heroin Cycle”) for individuals to use in overdose situations.
While naloxone is still the standard medication for emergency reversal of opioid overdose, its clinical use in long-term opioid addiction treatment is being superseded by naltrexone. Naltrexone (C20H23NO4) is structurally similar to naloxone (C19H21NO4), and samidorphan (C21H26N2O4). But it has a slightly increased affinity for κ-opioid receptors (KOR) and has a longer duration of action than naloxone. Naltrexone is used as a preventative medication for opioid use disorder in Vivitrol, whose marketing rights are owned by Askemet.
Samidorphan (ALKS-33) is also a full opioid antagonist, acting on the MOR receptor with mixed agonist-antagonist activity at the KOR receptor. Combining samidorphan with buprenorphine is supposed to block the agonist effect of buprenorphine on the MOR receptor, while not inhibiting the buprenorphine antagonist effect on the KOR receptor. A study by Shram et al. comparing samidorphan to naltrexone was published online ahead of the June 2015 issue of the Journal of Clinical Psychopharmacology. Samidorphin was found to have greater binding affinity than naltrexone to mu receptors and a longer half-life. This was suggestive of prolonged opioid receptor antagonism at lower doses of samidorphin. The study, though, was funded by Askemet.
Suboxone (buprenorphine and naloxone) and ALKS-5461 (buprenorphine and samidorphin) appear to be biochemical twins. And it does not seem to me that the addictive potential of buprenorphine has been entirely neutralized by its combination with samidorphin as claimed. The history of abuse and diversion with Suboxone supports this concern. If my fear is true, then in the name of treating depression, ALKS-5461 will create a huge population of individuals who become dependent upon buprenorphine.
Coming off of buprenorphine is not fun. Here is a personal testimony of someone tapering off of buprenorphine. Oh, and mood swings with bouts of anxiety or depression are common side effects with buprenorphine withdrawal.
Buprenorphine withdrawal symptoms last longer for those who use buprenorphine for longer periods of time or at higher doses. Additionally, those who use buprenorphine other than prescribed (snort, inject, chew) may experience more severe symptoms than someone taking buprenorphine as prescribed. In these cases, physical buprenorphine withdrawal symptoms can last weeks after stopping.However, psychological withdrawal symptoms can last for many months after cessation. It is recommended that you join a support group or see a psychologist who can help see you through the protracted or post acute withdrawal symptoms (PAWS). Many heavy buprenorphine users experience PAWS. With continued use of buprenorphine, there comes a point where the brain produces in an inadequate amount of neurotransmitters in the body. People going through buprenorphine PAWS manifest long lasting changes in the brain as a result of long term use.
The Substance Abuse and Mental Health Services Administration (SAMHSA) estimated that in 2013, 1.8 million people had an opioid use disorder; 517,000 of which had one related to heroin use. SAMHSA also estimated that each year, 9.1% of the adult population experience symptoms consistent with major depression. One 2012 study suggested that 10% to 30% of individuals with major depression suffer from treatment resistant depression. Using a U.S. population estimate of 320.94 million, with a median 20% for individuals with treatment resistant depression, that leaves a target population of over 5.84 million Americans with treatment resistant depression. God help us.
I don’t think it is too strong rhetorically to speak of a pending depression apocalypse. I hope I’m wrong. But widespread use of ALKS-5461 could instigate a huge population of individuals dependent upon buprenorphine. And the problems coming off of ALKS-5461 would eclipse what we now know happens with SSRI withdrawal. Within the biochemical worldview, these symptoms will be reinterpreted as evidence of the underlying depression and proof the individual needs to remain on ALKS-5461. Sound familiar?
