The pharmaceutical company Allergan recently announced to shareholders that a new drug they tested for depression did not perform better than a placebo in clinical trials.

The drug, rapastinel, will not be approved by the Food and Drug Administration (FDA) for depression. However, Allergan may choose to start testing the drug for opioid use disorder (OUD).

Researchers at Duke University presented some promising results at an Experimental Biology conference that ran from April 6 to 9, 2019. The researchers tested rapastinel in rats, and the drug appears to reduce opioid withdrawal symptoms. However, since the study was only in rats, more research needs to be done in humans to know if rapastinel is safe and effective for OUD.

Article at a Glance:

  • Rapastinel did not work for major depressive disorder in human clinical trials
  • Rapastinel works similar to ketamine, a drug for sedation and depression
  • Medication-assisted treatment (MAT) for opioid use disorder (OUD) is the only other opioid treatment available right now
  • Rapastinel appears to be safe and could be effective for OUD in future trials.

Rapastinel and Major Depressive Disorder (MDD)

Rapastinel is a selective NMDA receptor modulator, which means it works similarly to ketamine. Ketamine is normally used for hospital sedation, but it was approved for treating depression as a nasal spray.

Rapastinel is an injectable medication that was given once a week in the Allergan clinical trials. It appeared to have no significant side effects compared to a placebo in the trials. Therefore, rapastinel is likely safe for humans at the dose tested, but it does not seem to work for treating depression.

Rapastinel and Opioid Use Disorder (OUD)

OUD is the misuse of prescribed or non-prescribed opioid medications. OUD is a lifelong disorder characterized by chronic and increased consumption of opioid drugs. Examples of opioids include:

Symptoms of Opioid Withdrawal and OUD

Detox is the process of the body eliminating a drug from itself. If the body is used to having a drug all the time, withdrawal symptoms may develop due to the absence of the drug. Withdrawal symptoms include:

Medication Assisted Treatment

Medication-assisted treatment (MAT) is a type of treatment for OUD that uses medications to help ease withdrawal symptoms. Most MAT drugs are opioids themselves, but some block the actions of opioids. Examples include:

  • Buprenorphine: Buprenorphine targets opioid receptors, but less so than other opioids. Buprenorphine does not cause as much euphoria as other opioids do, so it treats symptoms of OUD with less potential for abuse.
  • Methadone: Methadone also activates opioid receptors and produces less euphoria. Methadone breaks down slowly and lasts five days in the body so it can be used for once-a-day treatment.
  • Naltrexone: Naltrexone is a daily medication that blocks other drugs from activating opioid receptors. Naltrexone is also formulated as a once-monthly injection.
  • Naloxone: Naloxone is useful for emergency situations like an overdose. It can be injected or inhaled.

The primary downside of current MAT drugs is they interact directly with opioid receptors and still have some potential for abuse. Naltrexone and naloxone cannot be abused, but if they are administered wrong they can cause emergency withdrawal symptoms.

Rapastinel does not activate opioid receptors, so it cannot be abused like other MAT drugs. If the drug works for OUD as a once-weekly injection, this could also provide a convenient dosing schedule for people who do not want to take something once a day.

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