What parameters should I monitor in patients on naltrexone (opioid receptor antagonist)?

From the Guidelines

You should monitor liver function tests at baseline and every three to six months in patients on naltrexone, as it has been associated with hepatic injury at supratherapeutic doses. When monitoring patients on naltrexone, it is essential to consider the potential risks and side effects associated with its use. According to the study published in the American Family Physician in 2013 1, naltrexone can cause hepatic injury, particularly at high doses. Therefore, regular monitoring of liver function tests, such as AST and ALT, is crucial to prevent and detect any potential liver damage.

Some key parameters to monitor in patients on naltrexone include:

• Liver function tests (AST, ALT) at baseline and every three to six months
• Signs of depression and suicidal ideation, as naltrexone may worsen these conditions in predisposed individuals
• Treatment adherence and efficacy by tracking cravings, substance use patterns, and relapse episodes
• Gastrointestinal side effects like nausea, vomiting, abdominal pain, and diarrhea
• Injection site reactions in patients receiving extended-release injectable naltrexone (Vivitrol)

It is also important to ensure that patients understand the risks associated with naltrexone use, including the potential for precipitated withdrawal if opioids are used and the reduced efficacy of opioids in emergency situations requiring pain management, as noted in the study 1. Baseline evaluation should include comprehensive liver function tests, screening for current opioid use, and ensuring the patient has been opioid-free for 7-10 days before initiating oral naltrexone or 7-14 days before injectable formulations to prevent precipitated withdrawal.

From the FDA Drug Label

Patients should be warned of the risk of hepatic injury and advised to seek medical attention if they experience symptoms of acute hepatitis Use of naltrexone hydrochloride should be discontinued in the event of symptoms and/or signs of acute hepatitis. Depression, suicide, attempted suicide and suicidal ideation have been reported in the postmarketing experience with naltrexone hydrochloride used in the treatment of opioid dependence. Alcohol-and opioid-dependent patients, including those taking naltrexone hydrochloride, should be monitored for the development of depression or suicidal thinking Naltrexone hydrochloride and its primary metabolite are excreted primarily in the urine, and caution is recommended in administering the drug to patients with renal impairment An increase in naltrexone AUC of approximately 5- and 10-fold in patients with compensated and decompensated liver cirrhosis, respectively, compared with subjects with normal liver function has been reported.

You should monitor the following parameters in patients on naltrexone:

• Liver function: due to the risk of hepatic injury and liver dysfunction 2
• Mental status: for signs of depression, suicidal thinking, or other mental status changes 2
• Renal function: in patients with renal impairment, as naltrexone is excreted primarily in the urine 2
• Opioid withdrawal symptoms: in patients transitioning from opioid agonists to naltrexone, as they may be vulnerable to precipitation of withdrawal symptoms 2 2

From the Research

Parameters to Monitor in Patients on Naltrexone

When patients are on naltrexone, an opioid receptor antagonist, several parameters should be monitored to ensure safe and effective treatment. These include:

• Liver function tests, such as serum glutamic oxalacetic transaminase (SGOT) and serum glutamic pyruvic transaminase (SGPT) levels, as naltrexone may cause elevations in these enzymes, indicating potential liver damage 3, 4, 5, 6.
• Aspartate aminotransferase and alanine aminotransferase levels, which can also indicate liver health and potential damage from naltrexone treatment 4, 6.
• Patients with liver disease, including those with cirrhosis, should be closely monitored, as naltrexone may be safe to use in these patients, but more safety data are needed, especially for those with decompensated cirrhosis 4.
• Opioid use and cravings, as patients on naltrexone may still attempt to use opioids, which can lead to increased risk of overdose or other adverse effects 7.
• Mental health and social adjustment, as challenging naltrexone blockade with heroin or other opioids is often associated with polydrug use and social adjustment problems 7.

Patient Subgroups Requiring Special Consideration

Certain patient subgroups may require special consideration when monitoring parameters during naltrexone treatment, including:

• Patients with liver disease, who may require more frequent monitoring of liver function tests 4.
• Older patients (aged 40 years and over), who may be more likely to develop elevations in serum transaminase values 5.
• Patients taking high doses of naltrexone, who may be at increased risk of liver damage and should be monitored closely 3, 5, 6.
• Patients with a history of impulse-control disorders, who may require monitoring for potential interactions between naltrexone and other medications 6.