Nursing care
Naltrexone: what to check before you give it
Written and reviewed by Dana Whitfield, RN, MSN · 5 min read · Updated September 2026
Short answer
Naltrexone is an opioid antagonist used for opioid or alcohol use disorder, and it blocks the opioid receptor completely. Because of that, the patient must be opioid-free for seven to ten days before the first dose, or the drug precipitates acute withdrawal. Nurses confirm this timeline and check a urine drug screen before administration, not after.
Why this drug and not another
Naltrexone is chosen over other options because it works by blockade rather than substitution. Unlike methadone or buprenorphine, it does not activate the opioid receptor at all, so it carries no abuse potential and no risk of causing euphoria. This makes it attractive for patients who want to avoid any opioid exposure during recovery, including those in safety-sensitive occupations.
It is also used off-label and on-label for alcohol use disorder, where it reduces the reinforcing, pleasurable effect of drinking rather than causing an aversive reaction the way disulfiram does. The choice between naltrexone and disulfiram for alcohol use disorder often comes down to whether the patient can reliably avoid alcohol accidentally, since naltrexone does not punish a slip the way disulfiram's reaction does.
Administration and timing
Naltrexone is available as a daily oral tablet or as a monthly extended-release intramuscular injection. Before any first dose, in either form, the patient must be confirmed opioid-free for seven to ten days for short-acting opioids, and longer for methadone or other long-acting agents, because residual opioid on the receptor is exactly what triggers the reaction this drug is built to prevent.
A naloxone challenge test may be used before starting naltrexone in patients whose opioid-free status is uncertain, since a positive challenge confirms opioid dependence is still present and naltrexone must be delayed. Once started, timing is straightforward: same time daily for oral tablets, or a set date each month for the injectable, with a reminder that missing the injection date does not reduce risk the way it does with the injectable antipsychotics, since naltrexone is a blocker, not a replacement.
Monitoring parameters
Baseline and periodic liver function tests are essential, since naltrexone carries a dose-dependent risk of hepatocellular injury. Confirm the seven-to-ten-day opioid-free window before the first dose using patient history and a urine drug screen, since patient self-report of last opioid use is frequently unreliable in this population.
Ongoing monitoring includes mood and mental state, since case reports have linked naltrexone to depressive symptoms in some patients, and injection-site monitoring for the extended-release formulation, where significant site reactions have occurred. There is no analgesic monitoring parameter in the usual sense, but the nurse should document that opioid analgesia will not work while naltrexone is on board, which matters directly for future surgical or trauma care planning.
Adverse effects to report
Precipitated opioid withdrawal is the adverse effect specific to this drug and the one most likely to appear on an exam: nausea, vomiting, diarrhea, abdominal cramping, sweating, tachycardia, and severe anxiety appearing within minutes to hours of the dose, in a patient who was not thought to have any opioid on board. This requires immediate supportive care and should prompt review of exactly what the patient took and when.
Hepatotoxicity presents as right upper quadrant pain, jaundice, dark urine, or unexplained fatigue and should be reported for further liver testing. Injection-site reactions with the extended-release form, ranging from mild induration to necrosis requiring surgical intervention, should be reported and the site documented at every visit.
Contraindications and cautions
Naltrexone is contraindicated in current opioid use or opioid dependence without the required opioid-free interval, in acute hepatitis or liver failure, and in patients currently requiring opioid analgesia for pain management. It should not be started in anyone using opioid-containing medications, including some cough and diarrhea preparations, without a full medication reconciliation.
Caution applies in any patient with a history of suicidal ideation or depression, given the reported association with mood symptoms, and in patients with a planned surgery, since opioid analgesics will be ineffective while naltrexone is active and alternative pain management must be planned in advance.
Teaching points the exam tests
The core teaching point, and the one most tested, is that naltrexone will precipitate withdrawal if opioids are still present, so the patient must be honest about the date of last use and understand why waiting matters more than starting treatment quickly. Expect a question where the correct nursing action is to verify the opioid-free interval and obtain a urine drug screen before administering the dose, not to proceed based on the patient's stated intent to be honest.
Patients also need to understand that if they relapse and use opioids while on naltrexone, a higher dose may be needed to overcome the blockade, and that this significantly raises overdose risk since tolerance has dropped. Carrying medical identification stating they take naltrexone is recommended in case of emergency surgery or trauma, so opioid analgesia is not attempted ineffectively or opioid antagonism is anticipated.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our mental health practice questions are the closest set to what this page covers.
Common questions
How long does a patient need to be opioid-free before starting naltrexone?
Generally seven to ten days for short-acting opioids such as heroin or oxycodone, and longer, often ten to fourteen days, for long-acting opioids like methadone. The exact window should be confirmed against current prescribing guidance for the specific opioid used.
What does precipitated withdrawal from naltrexone look like?
It presents rapidly, often within minutes of the dose, with nausea, vomiting, diarrhea, sweating, tachycardia, and severe anxiety. It differs from natural withdrawal mainly in its speed of onset and requires supportive symptomatic treatment.
Can naltrexone be used for alcohol use disorder as well as opioid use disorder?
Yes, it is approved for both. For alcohol use disorder it reduces the reinforcing effects of drinking rather than causing an aversive reaction, which distinguishes it from disulfiram.
Why would a patient on naltrexone need special pain management planning before surgery?
Because naltrexone blocks the opioid receptor, standard opioid analgesics will not be effective while it is active. The surgical and anesthesia team need advance notice so alternative pain control, and a plan for when naltrexone can safely be restarted, is arranged before the procedure.
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