NALTREXONE: OPIOID ANTAGONIST THERAPY

Naltrexone is an alternative treatment for opioid addiction. Unlike methadone or buprenorphine, which are both opioid agonists (with opioid-like effects), naltrexone is an opioid antagonist– meaning that it blocks opioid receptors in the brain instead of activating them. By blocking opioid receptors in the brain, naltrexone can prevent all effects of any opioid drugs taken while naloxone remains in a person’s system. This treatment blocks everything from a “high” to an overdose. Besides the obvious safety benefits of naltrexone, this “blocking “ effect can also give an addicted person time to “unlearn” patterns that lead to cravings and habits related to opioid abuse.

Patients who successfully transition to naltrexone use have much lower rates of relapse than patients who receive counseling alone.

Who is a candidate for Naltrexone treatment?

While agonist maintenance with buprenorphine or methadone remains the treatment of choice for opioid addiction, it does not work for everyone. Some patients do not like the idea of long-term use of opioid drugs. Long-term treatment with buprenorphine or methadone also remains controversial for the treatment of young people or for those with only a brief history of opioid addiction. Patients may also prefer naltrexone to agonist maintenance (buprenorphine or methadone) if they are highly motivated or are working in a profession in which agonist use is controversial. Patients who are interested in abstinence after trying agonist therapy may be good candidates for naltrexone. Abstinent patients that are at a high risk of relapse, such as those with acute or worsening psychiatric illness, may also benefit from naltrexone therapy.

Beginning Naltrexone Therapy

However, naltrexone treatment is more difficult to begin than other MAT drugs. It can be difficult to transition from active opioid use to a first dose of naltrexone. Because naltrexone is a strong opioid receptor antagonist, it can “kick out” other opioids from the brain and cause withdrawal symptoms. A person who is physically dependent on opioids needs to be abstinent from heroin for 5-7 days, or abstinent from methadone for 7-10 days, in order to begin naltrexone treatment. When naltrexone is begun under physician supervision, other medicines can be used make withdrawal less painful in the beginning stages of naltrexone treatment. Certain non-opioid “comfort” medicines to relieve withdrawal symptoms like muscle cramping, nausea, and insomnia. Some patients may need a higher level of support, such as an inpatient stay to begin naltrexone, if they have a more severe pattern of opioid use or a co-existing medical or psychiatric illness.

Risks of Naltrexone

Some dangers are associated with naltrexone use. Patients taking naltrexone have lost their tolerance to opioids, and will be at risk of accidental overdose if they drop out of treatment and stop taking naltrexone. One advantage of the long-acting injectable naltrexone (Vivitrol) is that is wears off slowly, so that there is no sudden loss of opioid blockade, thus reducing the risk of overdose.  It is expected that about half of naltrexone patients will “test” the effects of the drug by taking an opioid, but patients should not continue to use opioids during naltrexone treatment because of a greater risk of dropping out of therapy after treatment.

Vivitrol: Long-Acting Naltrexone

Naltrexone treatment has been difficult to use in the past. Before 2010, naltrexone was only available in the form of a once-daily pill, and it was often hard for patients to remember to take and keep up with their medication. The recent approval of a long-acting form of injectable naltrexone (Vivitrol) that only needs to be taken about once every month is much easier to maintain than the older oral form of naltrexone.

Naltrexone + Behavioral Therapy

Naltrexone therapy is more effective when combined with behavioral therapy that encourages lifestyle changes to support abstinence from opioids. Network Therapy (see later section), incentives for abstinence, and relapse prevention therapies may all benefit patients on naltrexone.

IS SUBOXONE (BUPRENORPHINE+ NALOXONE) USEFUL FOR METHADONE PATIENTS?

Because Suboxone treatment is safer and easier to use than methadone and does not require daily visits to methadone clinics, methadone patients may be interested in switching to buprenorphine.  However, because buprenorphine is a partial agonist, a patient maintained on methadone may find buprenorphine to be a “weaker” medication. Methadone patients may go into major withdrawal if they switch from a full dose of methadone to buprenorphine.  To avoid withdrawal, a methadone patient would first have to reduce the methadone dose  to 40 mg or less daily, often a difficult process with a high risk of relapse.

In some cases, buprenorphine may not be strong enough for patients used to high doses of methadone, and may lead to increased cravings and increased risk of relapse. Patients interesting in switching from methadone to buprenorphine should be aware of these risks and remain open to resuming methadone if necessary.

Persons currently addicted to prescriptions pain medications or heroin, as well as patients maintained with methadone, should not accept buprenorphine or Suboxone from a “friend,” as this medication will cause uncomfortable withdrawal symptoms. Always ask a physician before switching medications.