What labs are recommended for a patient with a history of opioid dependence or addiction prior to undergoing an ultrasound while being treated with Naltrexone (naltrexone hydrochloride)?

Laboratory Testing Prior to Naltrexone Initiation in Patients with Opioid Use Disorder

Baseline liver function tests (AST, ALT, total bilirubin, GGT, alkaline phosphatase) must be obtained before initiating naltrexone, with monitoring every 3-6 months thereafter due to potential hepatotoxicity at supratherapeutic doses. 1, 2

Pre-Treatment Laboratory Panel

The following labs are essential before starting naltrexone therapy:

Hepatic Function Assessment (Mandatory)

• Obtain comprehensive liver function tests including AST, ALT, total bilirubin, GGT, alkaline phosphatase, serum albumin, and total protein before initiating naltrexone 1, 2, 3
• Naltrexone carries hepatotoxicity risk, particularly at supratherapeutic doses, making baseline liver assessment critical 1, 2
• Naltrexone is contraindicated in patients with decompensated cirrhosis or acute hepatitis; alternative medications like baclofen or acamprosate should be used instead 2
• For patients with compensated cirrhosis or moderate hepatic impairment, assess treatment case-by-case considering risks versus benefits 2

Renal Function Assessment

• Screen for renal impairment with serum creatinine and estimated GFR 2
• Patients with moderate-to-severe renal impairment require dose reduction to 25 mg daily (half the standard dose) 2

Opioid Status Verification

• Confirm complete opioid abstinence for 7-10 days (short-acting opioids) before naltrexone initiation to avoid precipitating severe, potentially life-threatening withdrawal 1, 2, 4
• Urine drug screening is recommended to verify opioid-free status prior to first dose 5
• Be aware that naltrexone metabolite noroxymorphone can cause false-positive oxycodone results on urine drug screens; confirmatory testing should be used if positive results occur during treatment 6

Mental Health Screening

• Screen for depression, anxiety, and insomnia before initiating naltrexone, as it may cause or worsen depression 2, 4
• Assess for suicidal ideation or history of suicide attempts, as these are risk factors requiring closer monitoring 5

Ongoing Monitoring Schedule

• Repeat liver function tests every 3-6 months during naltrexone treatment 1, 2
• Research in patients with chronic hepatitis C and HIV infection showed that elevations in AST/ALT >3× upper limit of normal occurred but were not significantly different from placebo, and most improved with continued treatment 3, 7
• Long-term studies up to 36 months with doses up to 300 mg/day showed no significant hepatotoxicity in most patients 8

Critical Safety Considerations

Naltrexone cannot be used in any patient requiring opioids for pain management, as it functions as a competitive mu-opioid receptor antagonist that blocks all opioid effects including analgesia 1

Perioperative Planning

• Hold oral naltrexone for 2-3 days prior to elective procedures if opioids are expected 2, 4
• Extended-release naltrexone (Vivitrol) must be held for 24-30 days after the last injection before elective procedures 2, 4

Post-Discontinuation Risk

• Patients who discontinue naltrexone have decreased opioid tolerance and markedly increased risk of overdose and death if they return to previous opioid use 2, 4
• Provide opioid overdose education and offer naloxone to all patients discontinuing naltrexone 2, 4

Common Pitfalls to Avoid

• Do not initiate naltrexone without confirming adequate opioid-free period (7-10 days minimum), as precipitated withdrawal can be severe and life-threatening 1, 2, 4
• Do not use naltrexone in pregnant women with opioid use disorder; offer buprenorphine or methadone instead 1, 2
• Do not skip baseline liver function testing, even in patients without known liver disease, as hepatotoxicity monitoring is essential 1, 2
• Do not assume all positive opioid screens indicate relapse during naltrexone treatment; noroxymorphone (a naltrexone metabolite) can cause false-positive oxycodone results requiring confirmatory testing 6

Note on Ultrasound Procedures

The ultrasound procedure itself does not require any specific laboratory modifications related to naltrexone therapy. The labs discussed above are standard pre-treatment requirements for naltrexone initiation in patients with opioid use disorder, regardless of concurrent diagnostic procedures 1, 2, 4