Inpatient management of opioid use disorder: A review for hospitalists

Medication-Assisted Treatment

It is important to recognize that treatment of withdrawal is not adequate to prevent long-term opioid misuse.²⁵ The optimal long-term management of OUD includes the use of medication-assisted treatment (MAT). The initiation and titration of MAT should always be done in conjunction with an addiction specialist or buprenorphine-waivered physician who will ensure continuation of MAT as an outpatient. This means that, while hospitalists may be critical in facilitating linkage to MAT, in general, they will not have a significant role in the long-term management of OUD. However, hospitalists should be knowledgeable about MAT because it is relatively common and can complicate hospitalizations.

There are two types of MAT: opioid-agonist treatment (OAT) and opioid-antagonist treatment. Opioid-agonist treatment involves the use of methadone, a long-acting opioid agonist, or buprenorphine, a long-acting partial opioid agonist. These medications decrease the amount and severity of cravings and limit the euphoric effects of subsequent opioid use.¹⁷ Compared to abstinence-based treatment, OAT has been associated with increased retention in addiction treatment and employment, and reductions in incarceration, human immunodeficiency virus transmission, illicit drug use, opioid-overdose events, and mortality.^26-32An alternative to OAT is naltrexone, an opioid antagonist. Naltrexone for OUD is administered as a monthly depot injection that prevents the user from experiencing opioid intoxication or dependence, and is associated with sustained abstinence.^17,33,34 The authors strongly recommend that hospitalists discuss the benefits of MAT with hospitalized individuals with OUD. In addition, when appropriate, patients should receive consultation with, or referral to, an addiction specialist.

Adverse Effects of Methadone, Buprenorphine, and Naltrexone

The benefits of MAT are substantial, but there are adverse effects, potential drug-to-drug interactions, and patient-specific characteristics that may impact the inpatient management of individuals on MAT. Selected adverse effects of OAT are listed in Table 1. The adverse effects of naltrexone include nausea, vomiting, and transaminitis. It should also be noted that the initiation of buprenorphine and naltrexone may induce opioid withdrawal when administered to an opioid-dependent patient with recent opioid use. To avoid precipitating withdrawal, buprenorphine should be used only in individuals who have at least mild withdrawal symptoms or have completed detoxification,²⁰ and naltrexone should be used only in patients who have abstained from opioids for at least 7 to 10 days.³⁵

Opioid-agonist treatments are primarily metabolized by the cytochrome P450 3A4 isoenzyme system. Medications that inhibit cytochrome P450 3A4 metabolism such as fluconazole can result in OAT toxicity, while medications that induce cytochrome P450 3A4 metabolism such as dexamethasone can lead to withdrawal symptoms.¹⁸ If these interactions are unavoidable, the dose of methadone or buprenorphine should be adjusted to prevent toxicity or withdrawal symptoms. The major drug interaction with naltrexone is ineffective analgesia from opioids.

Another major concern with MAT is the risk of overdose-related deaths. As an opioid agonist, large doses of methadone can result in respiratory depression, while buprenorphine alone, due to its partial agonist effect, is unlikely to result in respiratory depression. When methadone or buprenorphine are taken with other substances that cause respiratory depression, such as benzodiazepines or alcohol, the risk of respiratory depression and overdose is significantly increased.^36,37 Overdose-related death with naltrexone usually occurs after the medication has metabolized and results from a loss of opioid tolerance.³⁸

Special Populations

Medication-assisted treatment in individuals with acute pain. Maintenance treatment with OAT does not provide sufficient analgesia to treat episodes of acute pain.³⁹ In patients on methadone maintenance, the maintenance dose should be continued and adjunctive analgesia should be provided with nonopioid analgesics or short-acting opioids.³⁹ The management of acute pain in individuals on buprenorphine maintenance is more complicated since buprenorphine is a partial opioid agonist with high affinity to the opioid receptor, which limits the impact of adjunctive opioids. The options for analgesia in buprenorphine maintenance treatment include 1) continuing daily dosing of buprenorphine and providing nonopioid or opioid analgesics, 2) dividing buprenorphine dosing into a 3 or 4 times a day medication, 3) discontinuing buprenorphine and treating with opioid analgesics, 4) discontinuing buprenorphine and starting methadone with nonopioid or opioid analgesics.³⁹ In cases where buprenorphine is discontinued, it should be restarted before discharge upon resolution of the acute pain episode. An individual with acute pain on naltrexone may require nonopioid analgesia or regional blocks. In these patients, adequate pain control may be challenging and require the consultation of an acute pain specialist.

Pregnant or breastfeeding individuals. Opioid misuse puts the individual and fetus at risk of complications, and abrupt discontinuation can cause preterm labor, fetal distress, or fetal demise.⁴⁰ The current standard is to initiate methadone in consultation with an addiction specialist.⁴⁰ There is evidence that buprenorphine can be used during pregnancy; however, buprenorphine-naloxone is discouraged.^18,40 Of note, use of OAT in pregnancy can result in neonatal abstinence syndrome, an expected complication that can be managed by a pediatrician.⁴⁰

Methadone and buprenorphine can be found in low concentrations in breast milk.⁴¹ However, according to the Academy of Breastfeeding Medicine’s clinical guidelines, women on stable doses of methadone and buprenorphine should be encouraged to breastfeed.⁴¹ Naltrexone enters breast milk and has potential adverse effects for the newborn. Either the mother should discontinue naltrexone or should not breastfeed.³⁵

Treatment of polysubstance misuse. Individuals with OUD may also misuse other substances. The concomitant use of opioids and other central nervous system depressants, such as alcohol and benzodiazepines, is especially worrisome as they can potentiate respiratory depression. The presence of polysubstance misuse does not preclude the use of MAT for the treatment of OUD. In those with comorbid alcohol use disorder, the use of naltrexone may be appealing as it can treat both alcohol use disorder and OUD. Given the complexities of managing polysubstance misuse, addiction specialists should be involved in the care of these patients.⁴² In addition, patients should be educated on the risks of polysubstance misuse, especially when it involves 2 central nervous system depressants.

Comorbid medical disease. In general, medical comorbidities do not significantly affect the treatment of OUD; however, dysfunction of certain organ systems may necessitate a dose reduction or discontinuation of MAT. Severe liver disease may result in decreased hepatic metabolism of OAT.^35,42 Prolonged QTc, or history of arrhythmia, may preclude the use of methadone.^17,35,42 In addition, chronic hypercapnic respiratory failure or severe asthma may be contraindications for the use of methadone in an unmonitored setting.³⁵ Kidney failure is not known to be a contraindication to MAT, and there is no consensus on the need for dose reduction of MAT with decreasing glomerular filtration rate; however, some authors recommend a 25% to 50% dose reduction of methadone when the glomerular filtration rate is less than 10 milliliters per minute.⁴³ There is no such recommendation with buprenorphine, although it has not been adequately studied in individuals with renal failure. Close monitoring for evidence of toxicity is prudent in individuals on MAT with acute or chronic renal failure.³⁵

Rural or resource-limited areas. There is a significant shortage of addiction treatment options in many regions of the United States. As of 2012, there were an estimated 2.3 million individuals with OUD; however, more than 1 million of these individuals do not have access to treatment.⁴⁴ As a result, many addiction treatment programs have wait lists that can last months or even years.⁴⁵ These shortages are especially apparent in rural areas, where individuals with OUD are particularly reliant upon buprenorphine treatment because of prohibitive travel times to urban-based programs.⁴⁶ To address this problem, new models of care delivery are being developed, including models incorporating telemedicine to support rural primary care management of OUD.⁴⁷