15.2 Opioid Use Disorder Drugs

Opioid use disorder is a chronic condition driven by changes in the brain's reward system. Repeated opioid use causes neuroadaptations that make it extremely difficult to stop without medical help. Understanding how these changes happen, and how medications counteract them, is central to providing effective nursing care for patients in treatment and recovery.

Opioid Use Disorder

Mechanisms of opioid use disorder

Opioids work by binding to and activating opioid receptors in the brain. The mu opioid receptors are the most clinically significant because they produce the rewarding effects (euphoria) and pain relief that drive repeated use.

With repeated exposure, the brain adapts in several ways:

• Dopamine flooding: Opioids trigger a surge of dopamine in the nucleus accumbens, the brain's reward center. This reinforces drug-seeking behavior because the brain learns to associate opioid use with an intense reward signal.
• Blunted natural reward: Over time, the reward system becomes less responsive to normal pleasurable stimuli like food, social connection, and achievement. This makes opioids feel like the only reliable source of relief or pleasure.
• Tolerance: The brain downregulates opioid receptors and adjusts its signaling, so progressively higher doses are needed to achieve the same analgesic or euphoric effects.
• Withdrawal: When opioid use is abruptly reduced or stopped, the noradrenergic system becomes dysregulated, releasing excess norepinephrine. This drives the physical withdrawal symptoms patients experience.

Signs of opioid use disorder

The hallmark of opioid use disorder is compulsive use despite negative consequences across legal, financial, and social domains. Key signs include:

• Increasing tolerance (needing higher doses for the same effect)
• Withdrawal symptoms when use is reduced or stopped:
  • Anxiety, restlessness, insomnia
  • Muscle aches, abdominal cramps, diarrhea
  • Nausea, vomiting, sweating
• Neglect of personal responsibilities at work, school, or home
• Continued use despite worsening physical or psychological health (e.g., infections, depression)
• Unsuccessful attempts to cut down or control use

Causes and diagnosis of opioid addiction

Several risk factors increase a person's vulnerability to opioid use disorder:

• Genetic predisposition: A family history of addiction significantly raises risk.
• Chronic pain conditions: Patients with back pain, fibromyalgia, or other persistent pain are more likely to receive opioid prescriptions and develop dependence.
• Mental health disorders: Depression, anxiety, and PTSD frequently co-occur with substance use disorders.
• Early opioid exposure: Being prescribed opioid pain medications, especially at a young age, is a common entry point.

Diagnosis follows the DSM-5 criteria, which require at least two of the specified symptoms within a 12-month period. These symptoms span tolerance, withdrawal, loss of control over use, and social or occupational impairment.

Two useful screening tools to know:

• Drug Abuse Screening Test (DAST): A broad screen for problematic drug use across substances.
• Current Opioid Misuse Measure (COMM): Specifically identifies aberrant behaviors in patients already taking opioid medications.

Neurobiology of opioid addiction

The brain naturally produces its own opioids, called endorphins, which modulate pain and contribute to feelings of well-being. Exogenous opioids hijack this system by producing a far more powerful dopamine response than endorphins ever could.

Chronic use doesn't just create tolerance and dependence. It also causes neuroplastic changes in the prefrontal cortex, impairing decision-making and impulse control. This is why addiction is classified as a brain disorder, not simply a matter of willpower. Patients genuinely have reduced capacity to resist cravings and make long-term decisions about their health.

Treatment of Opioid Use Disorder

Medications for opioid addiction treatment

Three medications form the foundation of medication-assisted treatment (MAT). Each works through a different mechanism at the opioid receptor, and that distinction matters for clinical decision-making.

Methadone

• Mechanism: Full opioid agonist that binds to and fully activates mu opioid receptors.
• Route: Oral (liquid or tablet), long-acting, providing stable blood levels over 24 hours.
• Clinical use: Reduces withdrawal symptoms and cravings by keeping opioid receptors occupied. Also blunts the effects of other opioids if the patient uses on top of it.
• Key restriction: Must be dispensed daily at a federally certified opioid treatment program (OTP). Patients cannot simply fill a prescription at a pharmacy.

Buprenorphine

• Mechanism: Partial opioid agonist with high receptor affinity but lower intrinsic activity than full agonists. This means it activates mu receptors enough to prevent withdrawal and reduce cravings, but has a ceiling effect on respiratory depression, making overdose less likely.
• Route: Sublingual or buccal (brand names include Suboxone and Zubsolv). Suboxone combines buprenorphine with naloxone to deter misuse by injection.
• Clinical use: Can be prescribed in office-based settings by qualified providers, making it more accessible than methadone. (The DATA 2000 waiver requirement has been eliminated as of 2023, broadening prescribing access further.)

Naltrexone

• Mechanism: Opioid antagonist that binds to opioid receptors and blocks their activation. It produces no opioid effects whatsoever.
• Route: Oral (daily) or long-acting intramuscular injection (Vivitrol, given monthly).
• Clinical use: Blocks the euphoric effects of opioids, so if a patient relapses, they won't feel the high. This reduces the reinforcement cycle.
• Critical requirement: The patient must be fully detoxified from opioids (typically 7-10 days opioid-free) before starting naltrexone. If given while opioids are still in the system, it will precipitate acute withdrawal, which can be severe.

Effects of opioid addiction treatments

Nursing care for opioid addiction patients

Assessment

1. Obtain a thorough history of opioid use, including substances, duration, route, and last use.
2. Evaluate current withdrawal symptoms using the Clinical Opiate Withdrawal Scale (COWS). This standardized tool scores symptoms like pupil dilation, GI distress, and restlessness to guide treatment timing.
3. Monitor vital signs (blood pressure, heart rate, respiratory rate) and assess pain levels using a numeric rating scale.
4. Screen for co-occurring mental health conditions and polysubstance use.

Planning

1. Collaborate with the healthcare team to develop an individualized treatment plan that includes both medication and behavioral therapy.
2. Set measurable goals for medication adherence and participation in counseling or support groups.

Implementation

1. Administer medications as prescribed. For buprenorphine, ensure the patient is in mild-to-moderate withdrawal before the first dose to avoid precipitated withdrawal.
2. Monitor for side effects, especially constipation, sedation, and respiratory depression.
3. Provide clear patient education on how the medication works, what to expect, and the importance of not supplementing with illicit opioids.
4. Encourage engagement with behavioral therapies and peer support (e.g., Narcotics Anonymous, SMART Recovery).

Evaluation

1. Assess treatment response through urine drug screens, self-reported cravings, and functional improvement (employment, relationships, health).
2. Modify the care plan as needed based on patient response, including dose adjustments or adding therapies.

Patient education on addiction treatments

Effective patient education covers several areas. Tailor the depth and language to each patient's readiness and understanding.

How the medications work:

• Methadone and buprenorphine activate opioid receptors at a controlled, steady level to prevent withdrawal and reduce cravings without producing the intense high of misused opioids.
• Naltrexone blocks opioid receptors entirely, so opioids won't produce euphoria if the patient relapses.

Adherence matters:

• Taking medications exactly as directed maintains consistent blood levels and therapeutic effects.
• Skipping doses can trigger withdrawal symptoms. Taking extra doses of methadone or buprenorphine risks respiratory depression and overdose.

Behavioral therapy is part of treatment:

• Counseling addresses the psychological and social factors that contribute to addiction, such as trauma, stress, and unhealthy coping patterns.
• Support groups provide community and accountability during recovery.

Side effects and safety:

• Common side effects (constipation, nausea, sedation) are manageable and often improve over time.
• Patients should seek immediate medical attention for signs of respiratory depression: slow or shallow breathing, extreme drowsiness, or difficulty waking.

Relapse prevention:

• Relapse is common and does not mean treatment has failed. It's a signal to reassess and adjust the treatment plan.
• Patients who stop naltrexone or methadone lose their tolerance quickly. Using the same opioid dose they previously tolerated can cause a fatal overdose. This is a critical safety point to reinforce.

Harm reduction:

• For patients who continue to use opioids, discuss naloxone (Narcan) access and how to use it in an overdose emergency.
• Encourage patients to never use alone and to avoid mixing opioids with benzodiazepines or alcohol.

Resources:

• SAMHSA National Helpline: 1-800-662-4357 (free, confidential, 24/7)
• SAMHSA treatment locator: findtreatment.gov