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Agonist Therapy vs Antagonist Therapy

Agonist and Antagonist therapies are effective evidence-based options in the medical treatment of drug addiction. A simple way to think about these concepts is that agonist therapy creates an action while antagonist therapy opposes an action.

Agonist Therapy

Agonist Antagonist ReceptorsA drug that is an agonist attaches itself to receptors in the brain, and then produces a chemical reaction. For example, heroin is an opioid agonist. It binds to opioid receptors that control pleasure and pain, the result being a feeling of euphoria and well being. Other examples of opioid agonists, sometimes referred to as “full agonists,” are oxycodone, morphine and opium.

In agonist therapy, physicians prescribe their patients agonist drugs that attach themselves to the same receptors as the addicted substance. The agonist drug creates a similar high, essentially impersonating the more addictive drug. For instance, buprenorphine is a commonly used agonist in the treatment of heroin addiction.

Buprenorphine is a “partial agonist.” While it binds tightly to opioid receptors in the brain, it does not have a “full agonist” effect like heroin. Because there is a ceiling effect to its action, patients using the medication do not develop a tolerance, but do become physiologically dependent.

Agonist therapy can help relieve painful withdrawal and continuous cravings, allowing patients to focus on therapy and long-term recovery. The downside to agonist drugs is that patients can develop a physiological dependence and a tolerance to the medication during their treatment.

The following is a list of commonly used agonist drugs:

Antagonist Therapy

While antagonist drugs also bind to receptors in the brain, there is not a similar high to the addictive drug. Antagonist drugs are used to block addictive drugs from activating the brain’s receptors.

Antagonist therapy has several benefits. Patients receiving antagonist drugs, such as Naltrexone, which is used in the treatment of opioid addiction, do not develop a tolerance to the medication. Additionally, antagonist drugs are not addictive in and of themselves.

However, antagonist therapy does not alleviate the craving for the addictive substance. If being treated for opioid addiction, patients run a high risk of overdose if they skip a prescribed antagonist dose and relapse during that time.

Commonly used antagonist drugs include:

  • Naltrexone is used in the treatment of opioid addiction
  • Naloxone is often used to stabilize patients suffering from opiate overdose

There are no agonist or antagonist therapies for the treatment of alcohol addiction. However, there are other options. Aversion therapy uses medications, such as Antabuse, which discourage patients from consuming alcohol. This treatment is particularly useful in relapse prevention.

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Medication Assisted Treatment


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