What it is:Naltrexone is a medication approved by the Food and Drug Administration (FDA) to treat opioid use disorder (OUD). It is available as a pill or as an injectable (see Vivitrol below).
How it works:Naltrexone is an opioid antagonist, meaning it binds to opioid receptors in the body and brain and blocks them. Therefore, if someone tries to take an opioid while on Naltrexone, their opioid receptor sites will be blocked and they won’t feel the effects of the opioid.
Dosage:Pill form: Your doctor should direct you on the specific dosing schedule but pills come in 50mg doses and the weekly dose is usually 350mg.
Injectable form: 380 mg, delivered intramuscularly once a month (every 4 weeks).
Revia (tablet form), Vivitrol (extended-release injectable suspension,
https://www.vivitrol.com/)
Other things to know:
Naltrexone is not an opioidNaltrexone is not addictive, and does not cause withdrawal symptoms with stop of use. Naltrexone blocks the euphoric and sedative effects of opioids such as heroin, morphine, and codeine. Naltrexone reduces and suppresses opioid cravings.There is no abuse or diversion potential with naltrexone.Naltrexone has been shown to reduce cravings and relapsesPatients should wait at least 7 days after their last use of short-acting opioids and 10 to 14 days for long-acting opioids, before starting naltrexone (otherwise you can go into
precipitated withdrawals - see below).
Main Risks: Risk of opioid overdose (see below), sudden opioid withdrawal (especially if taken before fully detoxing off opioids, see below), liver damage, hepatitis. For the injectable form (Vivitrol), there is also the risk of severe reaction at the injection site.
Risk of opioid overdose. You can accidentally overdose in two ways:
1) Naltrexone blocks the effects of opioids. If someone tries to overcome this block by taking large amounts of opioids, they can overdose.
2) Patients on naltrexone, who discontinue use or relapse after a period of abstinence, may have a reduced tolerance to opioids. Therefore, taking the same, or even lower doses of opioids used in the past can cause life-threatening consequences.
Risk of sudden opioid withdrawal. Precipitated withdrawal refers to withdrawal that’s caused by a medication, rather than abstinence. In precipitated withdrawal, the same withdrawal symptoms of diarrhea, nausea, vomiting, runny nose, goosebumps, chills, headaches usually occur however they happen much more quickly and intensely. This can make it feel exceptionally disorienting and painful. Precipitated withdrawal is like slamming on the brakes of a car to stop while spontaneous withdrawal (withdrawal that occurs when you stop using a substance) is like slowing down gradually to a stop. The same end result is achieved, but they are dramatically different experiences.Why does this happen?
You have opioid receptors or “locks” all over your body, but mainly in your brain and spinal cord. An opioid agonist or “key”, which includes things like morphine, fentanyl, and heroin, binds and activates — or unlocks — these opioid receptors and triggers a cascade of signals that produce the effects associated with opioids, including pain relief, warmth, and euphoria. Opioid antagonists, which include naloxone and naltrexone, work in the opposite direction. They bind to opioid receptors or “locks” but don’t activate it or “open it”, making it unusable to opioid agonists (including those already in your system) for several minutes or even hours. In people who are physically dependent on opioids, this sudden loss of signals from the opioid receptors triggers the symptoms of precipitated withdrawal.
Cost:
Oral form (Revia): The cost of oral naltrexone with prescription drug coverage can vary depending on the health insurance provider and your insurance policy. Some insurance plans may fully cover the cost. Without insurance, oral naltrexone can vary from $25 to $108 for a 30-day supply of 50 milligram (mg) tablets.
Injectable form (Vivitrol): Vivitrol is covered by many health insurance plans, including Medicaid, which may cover the full or partial cost of Vivitrol for opioid use disorder. Without insurance, vivitrol can cost over $1000 per shot. A reduced cost for Vivitrol may be available through a patient assistance program.
Choosing between oral form (Revia) and injectable form (Vivitrol):
The main differences between the oral form (tablet) and the injectable is how often you have to take it and the cost. The oral form is usually taken daily so for some patients, this may pose a challenge of medication adherence. The injectable form lasts a month so may be easier to adhere to. Those without insurance may find it very difficult to afford the injectable form as it’s much more expensive.
Which one has better success rates? Some studies show evidence of better outcomes for long acting injectable naltrexone compared to oral naltrexone. However, there are no published randomized controlled trials comparing outcomes for long acting injectable naltrexone versus oral naltrexone for opioid dependence. Therefore more research needs to be done before making definitive claims.