Opioid Use Disorders

Opioids 101 - Brain's Poppy Problem

• Classification:
  • Natural: Morphine, Codeine (from Papaver somniferum)
  • Semi-synthetic: Heroin, Oxycodone, Buprenorphine
  • Synthetic: Fentanyl, Methadone, Pethidine, Tramadol
• Mechanism of Action (MOA):
  • Agonists at opioid receptors: μ (mu), κ (kappa), δ (delta).
  • Primarily μ-receptor activation: analgesia, euphoria, respiratory depression, miosis.
  • Receptors are G-protein coupled (Gi/Go): ↓ cAMP, open K+ channels (hyperpolarization), close Ca2+ channels (↓ neurotransmitter release).
• Neurobiology of Addiction:
  • ↑ Dopamine in mesolimbic reward pathway (Ventral Tegmental Area to Nucleus Accumbens).
  • Chronic use leads to neuroadaptation: tolerance & withdrawal.

⭐ Buprenorphine is a partial μ-opioid agonist and κ-opioid antagonist, used in opioid de-addiction due to its ceiling effect on respiratory depression and milder withdrawal symptoms compared to full agonists like methadone or heroin. It can precipitate withdrawal if given to a patient on a full μ-agonist due to its high affinity and lower intrinsic activity at the μ-receptor.

OUD Unmasked - Spotting the Signs

• Opioid Intoxication:
  • Classic Triad: Coma, pinpoint pupils (miosis), respiratory depression.
  • Also: Drowsiness, slurred speech, euphoria, ↓BP, ↓HR.
  • ⚠️ Severe respiratory depression can be fatal.
• Opioid Withdrawal: (Distressing, rarely life-threatening)
  • Flu-like: Myalgia, fever, lacrimation, rhinorrhea, yawning.
  • GI: Nausea, vomiting, diarrhea, cramps.
  • CNS arousal: Mydriasis, piloerection ("gooseflesh"), insomnia, restlessness, anxiety.
  • Onset: Short-acting (e.g., heroin) 6-12h; Long-acting (e.g., methadone) 24-72h.
  • COWS (Clinical Opiate Withdrawal Scale) for severity.
• Diagnosis (DSM-5 for OUD):
  • Pattern of use causing significant distress/impairment.
  • Requires ≥2 of 11 criteria over 12 months (impaired control, social impairment, risky use, pharmacological).

  ⭐ Pupil response is a vital diagnostic clue: Miosis (pinpoint) in intoxication, Mydriasis (dilated) in withdrawal.

Crisis Control - Tackling Overdose & Withdrawal

Opioid Overdose

• Immediate: ABCs (Airway, Breathing, Circulation).
• Antidote: Naloxone 0.4-2 mg IV/IM/SC; repeat q2-3min.
  • Max 10 mg. No response? Re-evaluate diagnosis.
  • ⚠️ Renarcotization risk (naloxone short half-life).
• Supportive: O2, ventilation.

Opioid Withdrawal

• Assess: COWS (Clinical Opiate Withdrawal Scale).
  • Mild: 5-12; Mod: 13-24; Mod-Sev: 25-36; Sev: >36.
• Symptomatic Rx:
  • Clonidine 0.1-0.3 mg (autonomic; monitor BP).
  • NSAIDs (pain), Loperamide (diarrhea), Ondansetron (N/V).
• MAT Start: Buprenorphine (COWS >8-12).
  • Day 1: 2-4 mg, up to 8-12 mg.

⭐ Naloxone's short half-life (30-90 min) compared to many opioids (e.g., methadone) necessitates prolonged observation for renarcotization after initial reversal.

Road to Recovery - Long-Term MAT Strategies

• Methadone:
  • Full µ-opioid agonist.
  • Daily at Opioid Treatment Programs (OTPs).
  • Reduces cravings & withdrawal symptoms.
  • ⚠️ Risk: QTc prolongation, interactions.
• Buprenorphine:
  • Partial µ-opioid agonist; κ-antagonist.
  • Ceiling effect on respiratory depression.
  • Sublingual (SL), implant, LAI.
  • Often with naloxone to deter IV misuse.
• Naltrexone:
  • Opioid antagonist; blocks opioid effects.
  • Oral daily or LAI monthly.
  • Requires 7-10 days opioid-free period (precipitated withdrawal risk).
  • Non-addictive, no diversion risk.
• Psychosocial Support:
  • Essential adjunct (counseling, therapies).

⭐ Buprenorphine's availability in office-based settings (unlike methadone for OUD requiring OTPs) improves treatment access.

High‑Yield Points - ⚡ Biggest Takeaways

• Opioid intoxication triad: miosis (pinpoint pupils), respiratory depression, altered mental status. Antidote: Naloxone.
• Opioid withdrawal: severe flu-like symptoms (e.g., piloerection, mydriasis, diarrhea, lacrimation), not life-threatening.
• MAT is first-line: Methadone (long-acting full agonist), Buprenorphine (partial agonist), Naltrexone (antagonist).
• Buprenorphine can precipitate withdrawal if administered before opioid effects wear off.
• Naltrexone (oral/injectable) requires full detoxification; contraindicated in acute liver failure.
• Clonidine helps manage autonomic hyperactivity in withdrawal; Lofexidine is also FDA-approved for this purpose.