64.2 Opioid & Stimulant Use Disorders: MOUD & Harm Reduction

ABFM Family Medicine Certification Study Guide Exam

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1 Chapter 1: Exam Structure, Blueprint & Clinical Decision-Making

1.1 Exam Blueprint, FMCLA vs. One-Day Exam & Board Scoring 1.2 Clinical Reasoning, Test-Taking Strategy & Ambiguity Management 1.3 Evidence-Based Medicine & Clinical Practice Guidelines in Primary Care

2 Chapter 2: Healthcare Systems, Practice Management & Quality

2.1 Practice Management, Billing, Coding & Documentation 2.2 Quality Improvement, Patient Safety & Diagnostic Stewardship 2.3 Interprofessional Team-Based Care & Care Coordination

3 Chapter 3: Ethics, Law, Biostatistics & Health Equity

3.1 Medical Ethics, Informed Consent & Surrogate Decision-Making 3.2 Biostatistics, Clinical Epidemiology & Diagnostic Test Interpretation 3.3 Social Determinants of Health, Health Equity & Cultural Humility 3.4 Physician Wellness, Burnout Prevention & Professionalism

4 Chapter 4: Lifestyle Counseling & Behavior Change

4.1 Alcohol Use Screening & Brief Intervention 4.2 Illicit Drug & Cannabis Counseling 4.3 Tobacco & Vaping Cessation Counseling

5 Chapter 5: Nutrition, Physical Activity & Chronic Disease Prevention

5.1 Dietary Counseling for Obesity & Chronic Disease Prevention 5.2 Exercise Prescription & Physical Activity Counseling 5.3 Genetic Risk Assessment & Family History Counseling

6 Chapter 6: Routine Adult Immunizations

6.1 ACIP Adult Respiratory Vaccines: Influenza, COVID-19, RSV & Pneumococcal 6.2 ACIP Adult Non-Respiratory Vaccines: Tdap, Shingrix, HPV & Hep B 6.3 Immunizations in Special Populations: Pregnancy, Asplenia & Immunocompromise

7 Chapter 7: Pediatric Health Maintenance & Surveillance

7.1 Newborn Examination & Early Postnatal Care 7.2 Well-Child Care, Developmental Surveillance & Milestones 7.3 Pediatric & Adolescent Screening: Vision, Hearing, Anemia & Lead 7.4 Pediatric Oral Health, Dental Screening & Fluoride

8 Chapter 8: Behavioral Health & Safety Screening

8.1 Primary Care Depression, Anxiety & Behavioral Health Screening 8.2 Domestic Violence, Intimate Partner Violence & Firearm Safety 8.3 Occupational Health & Recreational Safety Counseling

9 Chapter 9: Adult Preventive Screening: Cardiovascular & Metabolic

9.1 Cardiovascular Disease & Hypertension Screening 9.2 Type 2 Diabetes Screening & Prediabetes Risk Stratification 9.3 Abdominal Aortic Aneurysm & Osteoporosis Screening

10 Chapter 10: Adult Cancer Screening: Breast & Gynecologic

10.1 Breast Cancer Screening & Risk-Assessment 10.2 Cervical Cancer Screening & ASCCP Algorithms 10.3 Skin Cancer Clinical Assessment & Counseling

11 Chapter 11: Adult Cancer Screening: Colorectal, Lung & Prostate

11.1 Colorectal Cancer Screening Modalities & Intervals 11.2 Lung Cancer Screening with Low-Dose CT 11.3 Prostate Cancer Screening & Shared Decision-Making

12 Chapter 12: Sexual Health, Infectious Disease Screening & Contraception

12.1 Sexual Health Counseling & Risk-Reduction Strategies 12.2 STI Screening: Chlamydia, Gonorrhea, Syphilis & Trichomoniasis 12.3 Bloodborne Infectious Disease Screening: HIV & Hepatitis C

13 Chapter 13: Reproductive Life Planning, Lactation & Preoperative Care

13.1 Preconception Planning & Comprehensive Contraception Management 13.2 Lactation Support & Breastfeeding Counseling 13.3 Preoperative Medical Evaluation & Pre-Participation Sports Exam

14 Chapter 14: Emergent Cardiovascular Conditions

14.1 Acute Coronary Syndromes & Myocardial Infarction 14.2 Acute Chest Pain Risk Stratification & Triage 14.3 Acute or Critical Valvular Heart Emergencies

15 Chapter 15: Cardiac Arrhythmias, Heart Failure & Hypertensive Crises

15.1 Acute Atrial & Ventricular Arrhythmias 15.2 Acute Decompensated Heart Failure & Cardiogenic Shock 15.3 Hypertensive Emergency & Urgency Management

16 Chapter 16: Vascular & Thromboembolic Emergencies

16.1 Pulmonary Embolism & Deep Vein Thrombosis 16.2 Acute Aortic Syndromes & Peripheral Vascular Emergencies 16.3 Critical Limb Ischemia & Acute Arterial Occlusion

17 Chapter 17: Neurologic Emergencies: Stroke & Altered Consciousness

17.1 Acute Ischemic Stroke & Intracranial Hemorrhage 17.2 Syncope Evaluation & Status Epilepticus 17.3 Acute Delirium, Encephalopathy & Severe Confusion

18 Chapter 18: Neurologic Trauma & Acute Cranial Emergencies

18.1 Concussion, Moderate-to-Severe TBI & Intracranial Injury 18.2 Thunderclap & Acute Severe Secondary Headaches 18.3 Acute Ophthalmologic Emergencies

19 Chapter 19: Acute Abdominal, Pelvic & Gastrointestinal Emergencies

19.1 Acute Abdominal & Pelvic Pain Triage 19.2 Upper & Lower Gastrointestinal Bleeding 19.3 Acute Hepatic Failure, Cholangitis & Severe Jaundice

20 Chapter 20: Acute Pulmonary & Airway Emergencies

20.1 Acute Hypoxic Respiratory Failure & ARDS 20.2 Severe Community-Acquired Pneumonia & Empyema 20.3 Acute Severe Epistaxis & Airway Obstruction

21 Chapter 21: Acute Traumatic Injuries & Wound Care

21.1 Major Trauma Resuscitation & Initial Assessment 21.2 Burn Assessment, Inhalation Injury & Resuscitation 21.3 Laceration Management, Complex Wounds & Animal Bites

22 Chapter 22: Acute Orthopedic & Musculoskeletal Emergencies

22.1 Acute Ambulatory Fractures & Initial Splinting 22.2 Compartment Syndrome & Major Orthopedic Trauma 22.3 Septic Arthritis & Acute Microcrystalline Crises

23 Chapter 23: Severe Infections, Sepsis & Systemic Emergencies

23.1 Sepsis, Septic Shock & Initial Fluid Resuscitation 23.2 Necrotizing Soft Tissue Infections & Severe CNS Infections 23.3 Anaphylaxis Diagnosis, Epinephrine Dosing & Airway Protection

24 Chapter 24: Metabolic, Endocrine & Electrolyte Emergencies

24.1 Diabetic Ketoacidosis & Hyperosmolar Hyperglycemic State 24.2 Critical Electrolyte Emergencies: Dyskalemias & Dysnatremias 24.3 Severe Calcium Abnormalities & Acute Adrenal Crisis

25 Chapter 25: Hematologic, Urologic & Dental Emergencies

25.1 Severe Symptomatic Anemias & Coagulopathic Emergencies 25.2 Testicular Torsion, Priapism & Acute Urinary Retention 25.3 Urgent Odontogenic Infections & Dental Trauma

26 Chapter 26: Psychiatric, Behavioral & Obstetric/Gynecologic Emergencies

26.1 Suicidal Ideation, Acute Agitation & Behavioral Emergencies 26.2 Acute Physical & Sexual Assault Care 26.3 Life-Threatening Vaginal Bleeding & Ectopic Pregnancy 26.4 Environmental Heat Stroke & Severe Hypothermia

27 Chapter 27: Acute Head, Neck & Neurologic Symptoms

27.1 Primary Acute Headaches: Migraine, Tension & Cluster 27.2 Concussion & Minor Closed Head Injury Evaluation 27.3 Transient Ischemic Attack Evaluation & ABCD2 Risk Scoring

28 Chapter 28: Acute Cranial Nerves, Hearing & Sensory Symptoms

28.1 Peripheral Neuropathies: Bell's Palsy, Carpal Tunnel & Radiculopathy 28.2 Acute Tinnitus, Sudden Sensorineural Hearing Loss & Cerumen Impaction 28.3 Acute Dizziness, Benign Paroxysmal Positional Vertigo & Vestibular Neuritis

29 Chapter 29: Acute Upper Respiratory Tract Infections

29.1 Acute Viral Rhinosinusitis vs. Bacterial Rhinosinusitis 29.2 Acute Pharyngitis: Group A Streptococcus & Centor Criteria 29.3 Acute Otitis Media, Otitis Externa & Serous Effusion

30 Chapter 30: Acute Lower Respiratory Infections & Cough

30.1 Influenza, COVID-19 & Viral Respiratory Syndromes 30.2 Acute Bronchitis & Lower Respiratory Tract Infections 30.3 Ambulatory Community-Acquired Pneumonia

31 Chapter 31: Allergic, Nasal & Non-Infectious Pulmonary Conditions

31.1 Allergic Rhinitis & Acute Non-Anaphylactic Allergic Reactions 31.2 Acute Dyspnea in Ambulatory Care 31.3 Interstitial Lung Diseases & Sarcoidosis Presentation

32 Chapter 32: Acute Chest, Cardiac & Vascular Symptoms

32.1 Palpitations Evaluation & Arrhythmia Triage in Primary Care 32.2 Deep Vein Thrombosis & Superficial Thrombophlebitis 32.3 Ambulatory Hypotension & Orthostasis Evaluation

33 Chapter 33: Acute Upper Gastrointestinal Conditions

33.1 Peptic Ulcer Disease & Gastritis 33.2 Dysphagia, Esophagitis & Acute Esophageal Disorders 33.3 Acute Nausea, Vomiting & Foodborne Illness

34 Chapter 34: Acute Lower Gastrointestinal Conditions

34.1 Acute Infectious Diarrhea & Gastroenteritis 34.2 Acute Constipation & Functional Bowel Changes 34.3 Ano-Rectal Disorders: Hemorrhoids, Fissures, Abscesses & Pruritus Ani

35 Chapter 35: Inflammatory, Functional & Malabsorptive GI Disorders

35.1 Acute Flares of Inflammatory Bowel Disease 35.2 Irritable Bowel Syndrome: Diagnosis, Subtyping & Management 35.3 Celiac Disease & Malabsorption Syndromes

36 Chapter 36: Acute Abdominal, Hepatic & Biliary Disorders

36.1 Ambulatory Abdominal & Pelvic Pain Triage 36.2 Acute Cholecystitis, Biliary Colic & Pancreatitis 36.3 Acute Liver Injury & Viral Hepatitis

37 Chapter 37: Acute Abdominal Wall, Hernias & Dental Conditions

37.1 Abdominal Wall, Inguinal & Ventral Hernias 37.2 Acute Dental Pain, Odontogenic Abscess & Aphthous Ulcers 37.3 Acute Edema: Unilateral vs. Bilateral Diagnostic Evaluation

38 Chapter 38: Acute Infectious Dermatoses

38.1 Bacterial Skin Infections: Impetigo, Cellulitis & Cutaneous Abscesses 38.2 Fungal Skin Infections: Tinea Corporis, Cruris, Pedis & Onychomycosis 38.3 Viral Cutaneous Infections: Herpes Simplex, Zoster & Molluscum Contagiosum

39 Chapter 39: Inflammatory, Allergic & Autoimmune Dermatoses

39.1 Atopic Dermatitis, Contact Dermatitis & Eczematous Flares 39.2 Non-Infectious Rashes: Urticaria, Drug Eruptions & Erythema Multiforme 39.3 Cutaneous Malignancies & Premalignant Lesions: AK, BCC, SCC & Melanoma

40 Chapter 40: Acute Shoulder, Elbow & Upper Extremity Injuries

40.1 Rotator Cuff Pathology, Tendinopathy & Shoulder Impingement 40.2 Lateral & Medial Epicondylitis, Olecranon Bursitis & Elbow Sprains 40.3 Wrist & Hand Soft-Tissue Injuries: De Quervain, TFCC & Finger Sprains

41 Chapter 41: Acute Knee, Ankle & Lower Extremity Injuries

41.1 Meniscal Tears, Ligamentous Knee Injuries & Patellofemoral Pain 41.2 Ankle Sprains, Ottawa Ankle Rules & Achilles Tendinopathy 41.3 Plantar Fasciitis, Shin Splints & Overuse Syndromes

42 Chapter 42: Acute Ambulatory Fractures & Dislocations

42.1 Distal Radius, Scaphoid & Common Upper Extremity Fractures 42.2 Metatarsal, Clavicle & Common Lower Extremity Fractures 42.3 Joint Dislocation Management: Nursemaid's Elbow & Shoulder Subluxation

43 Chapter 43: Acute Axial Musculoskeletal Pain & Falls

43.1 Acute Low Back Pain: Red Flags, Strain & Disc Herniation 43.2 Acute Cervical Strain, Whiplash & Axial Neck Pain 43.3 Evaluation of Falls in Ambulatory & Older Patients

44 Chapter 44: Acute Inflammatory Arthropathies & Generalized Pain

44.1 Acute Inflammatory Arthritis & Spondyloarthropathies 44.2 Myalgias, Rhabdomyolysis & Post-Viral Pain Syndromes 44.3 Acute Non-Headache Pain Management Strategies

45 Chapter 45: Acute Renal, Urinary & Genitourinary Conditions

45.1 Uncomplicated UTI, Pyelonephritis & Acute Urethritis 45.2 Hematuria Workup & Glomerulonephritis 45.3 Nephrolithiasis & Acute Urinary Tract Obstruction

46 Chapter 46: Acute Male Genitourinary & Prostatic Conditions

46.1 Acute Prostatitis, Epididymitis & Orchitis 46.2 Acute Scrotal Pain: Torsion vs Appendage, BPH & Male Genital Emergencies 46.3 Acute Urinary Retention & Incontinence Evaluation

47 Chapter 47: Acute Women's Health & Early Pregnancy Care

47.1 Early Pregnancy Diagnosis, Dating & Initial Complications 47.2 Abnormal Uterine Bleeding & Acute Menstrual Disorders 47.3 Premenstrual Syndrome & Premenstrual Dysphoric Disorder

48 Chapter 48: Breast Disorders, STIs & Pediatric Elimination

48.1 Palpable Breast Mass, Mastitis & Nipple Discharge 48.2 Sexually Transmitted Infections: Diagnosis, Staging & CDC Guidelines 48.3 Pediatric Enuresis & Encopresis

49 Chapter 49: Systemic Signs, Metabolic Dysregulation & Miscellaneous Infections

49.1 Acute Fever, Sepsis Screening & FUO in Primary Care 49.2 Acute Hyperglycemia & Symptomatic Hypoglycemia 49.3 Electrolyte Abnormalities: Mild-to-Moderate Disturbances 49.4 Vector-Borne, Tick-Borne & Rickettsial Illnesses

50 Chapter 50: Chronic Cardiovascular Diseases: Hypertension & Ischemia

50.1 Essential Hypertension Management: 2025 AHA/ACC Guideline & JNC Strategies 50.2 Chronic Coronary Artery Disease & Post-MI Secondary Prevention 50.3 Chronic Heart Failure: HFrEF, HFpEF & Quadruple GDMT

51 Chapter 51: Chronic Vascular, Valvular & Dyslipidemic Diseases

51.1 Peripheral Arterial Disease & Claudication 51.2 Chronic Valvular Heart Disease & Murmur Evaluation 51.3 Lipid Disorders & ASCVD Risk-Based Statin Therapy

52 Chapter 52: Chronic Respiratory Diseases: Asthma & COPD

52.1 Chronic Asthma Management: GINA Stepwise SMART Therapy 52.2 Chronic Obstructive Pulmonary Disease: GOLD Recommendations 52.3 Solitary Pulmonary Nodule Evaluation & Fleischner Society Criteria

53 Chapter 53: Chronic Metabolic Diseases: Diabetes Mellitus

53.1 Type 2 Diabetes Management: ADA Pharmacotherapy Algorithms 53.2 Type 1 Diabetes: Basal-Bolus Insulin, CGMs & Diabetic Complications 53.3 Diabetic Microvascular & Macrovascular Disease Surveillance

54 Chapter 54: Obesity, Nutrition & Metabolic Bone Diseases

54.1 Medical & Behavioral Management of Obesity & Incretin Mimetics 54.2 Osteoporosis & Metabolic Bone Disease: DEXA, FRAX & Antiresorptives 54.3 Nutritional Deficiencies: Vitamin D, B12, Iron & Malnutrition

55 Chapter 55: Chronic Endocrine Disorders

55.1 Primary & Subclinical Hypothyroidism, Hyperthyroidism & Nodules 55.2 Adrenal Disorders: Addison's Disease & Cushing's Syndrome 55.3 Hypercalcemia, Hyperparathyroidism & Pituitary Disorders

56 Chapter 56: Chronic Kidney Disease & Venous Disorders

56.1 Chronic Kidney Disease: KDIGO Staging & Renoprotective Therapy 56.2 Chronic Venous Insufficiency, Stasis Dermatitis & Lymphedema 56.3 Chronic Electrolyte & Acid-Base Management in CKD

57 Chapter 57: Chronic Gastrointestinal & Hepatic Diseases

57.1 Gastroesophageal Reflux Disease, Barrett's Esophagus & Dyspepsia 57.2 Chronic Liver Disease: MASLD/NAFLD, Cirrhosis & Portal Hypertension 57.3 Viral Hepatitis B & C: Long-Term Monitoring & DAA Therapy

58 Chapter 58: Colorectal Surveillance & Chronic Pancreaticobiliary Care

58.1 Post-Polypectomy Colorectal Polyp Surveillance Guidelines 58.2 Chronic Pancreatitis & Exocrine Pancreatic Insufficiency 58.3 Chronic Nausea, Gastroparesis & Functional GI Disorders

59 Chapter 59: Chronic Musculoskeletal & Rheumatologic Disorders

59.1 Osteoarthritis: Hip, Knee & Hand Management 59.2 Spinal Conditions: Spinal Stenosis, Spondylolisthesis & Compression Fractures 59.3 Chronic Myopathies & Fibromyalgia Syndrome

60 Chapter 60: Chronic Neurologic & Neurodegenerative Disorders

60.1 Dementia: Alzheimer's, Vascular & Lewy Body Disease 60.2 Parkinson's Disease & Essential Tremor 60.3 Epilepsy: Chronic Antiseizure Medications & Post-Stroke Care

61 Chapter 61: Chronic Peripheral Nerves, Pain & Sensory Disorders

61.1 Diabetic & Chronic Peripheral Neuropathies 61.2 Chronic Pain Syndromes & Chronic Daily Headaches 61.3 Chronic Tinnitus, Presbycusis & Persistent Dizziness

62 Chapter 62: Chronic Psychiatric Disorders

62.1 Major Depressive Disorder & Generalized Anxiety Disorder 62.2 Bipolar Disorder: Maintenance Pharmacotherapy & Lithium Monitoring 62.3 Adult & Pediatric Attention-Deficit/Hyperactivity Disorder

63 Chapter 63: Chronic Behavioral Health & Neurodevelopmental Conditions

63.1 Chronic Behavioral Conditions: PTSD, OCD & Somatization 63.2 Autism Spectrum Disorder & Intellectual Disabilities 63.3 Eating Disorders: Anorexia Nervosa, Bulimia & Binge Eating

64 Chapter 64: Chronic Substance Use Disorders & Tobacco Cessation

64.1 Alcohol Use Disorder: Pharmacotherapy & Relapse Prevention 64.2 Opioid & Stimulant Use Disorders: MOUD & Harm Reduction 64.3 Longitudinal Tobacco Cessation Pharmacotherapy

65 Chapter 65: Chronic Dermatologic Conditions

65.1 Acne Vulgaris, Rosacea & Seborrheic Dermatitis 65.2 Chronic Plaque Psoriasis & Biologic Therapies 65.3 Chronic Eczema, Hidradenitis Suppurativa & Cutaneous Lupus

66 Chapter 66: Chronic Reproductive, Infectious & Geriatric Special Care

66.1 Chronic Menstrual Disorders, Infertility & Sexual Dysfunction 66.2 Menopause Management & Hormone Replacement Therapy 66.3 Chronic HIV Infection Management & Primary Care Integration 66.4 Gender-Affirming Primary Care & Hormone Therapy 66.5 Advance Care Planning, Palliative Care & End-of-Life Symptom Control

67 Chapter 67: Continuity Care: Sleep, Fatigue, Cancer, Pregnancy & the Adult Preventive Visit

67.1 Chronic Insomnia & Obstructive Sleep Apnea 67.2 Chronic Malaise, Fatigue & ME/CFS 67.3 Primary Care During Cancer Treatment & Survivorship 67.4 Routine Prenatal Care & Longitudinal Pregnancy Management 67.5 The Periodic Adult Health Examination & Medicare Annual Wellness Visit

64.2 Opioid & Stimulant Use Disorders: MOUD & Harm Reduction

Key Takeaways Explain This Topic AI

Medications for Opioid Use Disorder (MOUD)—specifically buprenorphine and methadone—are Grade 1A interventions that reduce all-cause mortality by >50%, suppress illicit opioid use, improve treatment retention, and decrease transmission of HIV and hepatitis C virus.

Under the federal MAT Act, the DEA X-waiver has been eliminated; any clinician with a standard Schedule III DEA registration can now prescribe buprenorphine for opioid use disorder in primary care.

Standard buprenorphine induction mandates objective mild-to-moderate opioid withdrawal (COWS score ≥8–12) prior to the initial dose to prevent precipitating severe acute withdrawal; low-dose buprenorphine induction (Bernese method) provides an alternative without requiring prior withdrawal.

Methadone is a full mu-opioid agonist requiring daily observed dispensing through federally licensed Opioid Treatment Programs (OTPs) and baseline/periodic ECG monitoring due to dose-dependent QTc prolongation; extended-release naltrexone requires a mandatory 7–14 day opioid-free period to prevent precipitated withdrawal.

Co-prescribing naloxone 4 mg intranasal spray is standard of care for all patients with OUD or high overdose risk (≥50 MME/day, concurrent sedatives); for stimulant use disorders, no FDA-approved medications exist, and Contingency Management represents the evidence-based gold standard.

Last updated: September 2026

Opioid Use Disorder & The Modern Synthetic Opioid Era

The opioid overdose epidemic in North America has evolved through three distinct waves: prescription opioids (1990s), heroin resurgence (2010), and the current predominance of illicitly manufactured synthetic opioids, primarily fentanyl and its analogues (carfentanil, acetylfentanyl). Fentanyl is 50 to 100 times more potent than morphine, highly lipophilic, and rapidly permeates the central nervous system. Its high lipophilicity causes it to accumulate in adipose tissue with chronic use, prolonging its terminal elimination and significantly complicating standard buprenorphine induction protocols.

DSM-5 Diagnostic Criteria for Opioid Use Disorder (OUD)

OUD is defined by a problematic pattern of opioid use leading to clinically significant impairment or distress, manifested by at least 2 of 11 criteria over a 12-month period across four behavioral domains:

Impaired Control : Using larger amounts or over longer periods than intended; persistent desire or unsuccessful efforts to cut down; spending excessive time obtaining, using, or recovering; intense craving.

Social Impairment : Failure to fulfill major role obligations (work, school, home); continued use despite interpersonal problems; giving up important activities.

Risky Use : Recurrent use in physically hazardous situations; continued use despite persistent physical or psychological harm.

Pharmacological Adaptations : Tolerance and withdrawal. DSM-5 SEVERITY STRATIFICATION FOR OUD

• Severity Staging Criteria Count Primary Care Clinical Implications
• ══════════════════════════════════════════════════════════════════════════════════════════════════════════

Mild OUD 2 to 3 criteria Initiate brief counseling, harm reduction, consider MOUD.

──────────────────────────────────────────────────────────────────────────────────────────────────────

Moderate OUD 4 to 5 criteria Strong indication for immediate MOUD (Buprenorphine or Methadone).

──────────────────────────────────────────────────────────────────────────────────────────────────────

Severe OUD ≥ 6 criteria High risk of fatal overdose; urgent MOUD, wrap-around psychosocial care.

══════════════════════════════════════════════════════════════════════════════════════════════════════════

Important

The Medical Supervision Exemption Rule Tolerance and withdrawal criteria DO NOT COUNT toward the diagnosis of OUD if the patient is taking opioid medications solely under appropriate medical supervision for chronic pain. An individual taking chronic prescribed opioids who exhibits physical dependence without loss of control, cravings, or functional impairment does not have OUD.

Medications for Opioid Use Disorder (MOUD)

Medications for Opioid Use Disorder (MOUD; formerly termed Medication-Assisted Treatment [MAT]) represent the definitive standard of care for moderate-to-severe OUD ( Grade 1A recommendation ). MOUD treatment:

Reduces all-cause mortality by greater than 50% , primarily by slashing fatal overdose rates.

Increases retention in addiction treatment programs.

Drastically decreases illicit opioid consumption.

Lowers criminal justice involvement.

Decreases transmission of bloodborne pathogens, specifically HIV and Hepatitis C virus (HCV) . COMPARATIVE PHARMACOLOGY OF MOUD AGENTS

Feature Buprenorphine / Naloxone Methadone Extended-Release Naltrexone

═══════════════════════════════════════════════════════════════════════════════════════════════════════════════════

• Receptor Activity High-affinity PARTIAL High-affinity FULL High-affinity PURE
• mu-opioid receptor agonist mu-opioid receptor agonist mu-opioid receptor ANTAGONIST
• ───────────────────────────────────────────────────────────────────────────────────────────────────────────
• Intrinsic Efficacy Intermediate (~40–50%); Full (100%); activates Zero; blocks all receptor
• exhibits ceiling effect downstream signaling without activation by endogenous
• on respiratory depression ceiling limit or exogenous opioids
• ───────────────────────────────────────────────────────────────────────────────────────────────────────────
• Formulation Sublingual tablet / film Oral liquid concentrate / Intramuscular depot injection
• (Suboxone; 4:1 ratio); tablets (dispensed daily at (Vivitrol 380 mg every
• monthly SQ depot (Sublocade) licensed OTP facilities) 4 weeks)
• ───────────────────────────────────────────────────────────────────────────────────────────────────────────
• Prescribing / ANY clinician with standard Restricted to federally Any licensed clinician;
• Regulatory Status Schedule III DEA registration certified Opioid Treatment no DEA schedule restriction
• (X-WAIVER ELIMINATED) Programs (42 CFR Part 8) (non-controlled substance)
• ───────────────────────────────────────────────────────────────────────────────────────────────────────────
• Overdose Protection Ceiling effect on respiratory Risk of overdose during No intrinsic overdose risk;
• Profile depression; safe in overdose titration; additive toxicity high fatal overdose risk if
• unless mixed with sedatives with other CNS depressants patient lapses after washout
• ───────────────────────────────────────────────────────────────────────────────────────────────────────────
• Initiation Window Requires active withdrawal Can be initiated immediately; Strict 7–10 day opioid-free
• (COWS ≥ 8–12) to avoid start low (20–30 mg) and window (14 days for methadone/
• precipitated withdrawal titrate slowly over weeks buprenorphine); negative UDS
• ───────────────────────────────────────────────────────────────────────────────────────────────────────────
• Safety / Monitoring Minimal organ toxicity; Baseline & periodic ECG for Baseline liver function tests;
• monitor baseline LFTs QTc prolongation; CYP3A4 contraindicated in acute liver
• drug-drug interactions failure or active hepatitis

═══════════════════════════════════════════════════════════════════════════════════════════════════════════════

1. Buprenorphine (Suboxone, Subutex, Sublocade)

Pharmacology : Buprenorphine is a partial mu-opioid receptor agonist with exceptionally high receptor binding affinity ( K i ≈ 0.2 nM K_i \approx 0.2\text{ nM} K i ​ ≈ 0.2 nM ) and slow receptor dissociation kinetics, coupled with competitive antagonism at kappa-opioid receptors.

Partial Agonism : It satisfies mu-opioid receptors enough to suppress cravings and abolish withdrawal symptoms without producing euphoria in opioid-tolerant individuals.

Ceiling Effect : Its partial intrinsic activity creates a distinct ceiling effect on respiratory depression and euphoria at therapeutic doses ( > 16 mg/day >16\text{ mg/day} > 16 mg/day ). Unlike full agonists, increasing the buprenorphine dose does not proportionally increase respiratory depression, conferring an extraordinary safety profile.

Suboxone Rationale (4:1 Buprenorphine:Naloxone Formulation) :

Naloxone is added solely as an abuse deterrent against intravenous diversion .

When taken sublingually as prescribed, naloxone has virtually zero bioavailability ( < 3 % <3\% < 3% ) due to near-complete first-pass hepatic glucuronidation, allowing buprenorphine to exert its therapeutic effect unimpeded.

If the combination tablet or film is crushed and injected intravenously or snorted, naloxone reaches brain mu receptors with high bioavailability, immediately neutralizing opioid action and precipitating intense, agonizing withdrawal.

Elimination of the Federal X-Waiver :

Under the Mainstreaming Addiction Treatment (MAT) Act passed by Congress in the Consolidated Appropriations Act of 2023, the historical requirement for clinicians to complete specialized training and apply for a federal DATA 2000 "X-waiver" was permanently eliminated .

Current Practice Standard : Any clinician (physician, nurse practitioner, physician assistant) with a standard DEA registration that includes Schedule III authority can prescribe buprenorphine for OUD without patient census caps or additional bureaucratic hurdles.

Clinical Management of Buprenorphine Induction MECHANISM OF BUPRENORPHINE-PRECIPITATED WITHDRAWAL

[Scenario A: Full Agonist Occupancy] [Scenario B: Buprenorphine Administered Too Early]

• Full Agonist (Heroin / Fentanyl) Buprenorphine (Partial Agonist: High Affinity / Low Intrinsic)
• High intrinsic activity (100%) • Displaces full agonist from receptor
• Maximum receptor activation • Drops net receptor stimulation from 100% down to 40%
• ═══════════════════════════════════════════════════════════

RESULT: ACUTE PRECIPITATED WITHDRAWAL COLLAPSE!

A. Standard Buprenorphine Induction

To avoid precipitating acute withdrawal, the patient must stop taking full-agonist opioids and wait until they enter objective mild-to-moderate withdrawal before the first buprenorphine dose is administered.

Clinical Opiate Withdrawal Scale (COWS) : Validated 11-item clinical scale scoring resting pulse rate, sweating, restlessness, pupil size, bone/joint aches, rhinorrhea/crying, GI upset, tremor, yawning, gooseflesh skin (piloerection), and anxiety/irritability.

Induction Threshold : Patient must achieve a COWS score ≥ 8 − 12 \ge 8-12 ≥ 8 − 12 before taking buprenorphine.

Short-acting opioids (heroin, immediate-release oxycodone): Typically 12 to 24 hours after last use.

Long-acting opioids (methadone, sustained-release morphine): Typically 36 to 72 hours after last use.

Fentanyl: Highly variable due to tissue storage; often requires 24 to 48 hours or utilization of low-dose induction.

Induction Dosing Protocol :

Day 1 : Initial dose of 2 to 4 mg sublingual buprenorphine. Observe patient for 60 to 90 minutes. If withdrawal symptoms improve and no precipitation occurs, administer an additional 2 to 4 mg every 2 hours as needed (target total Day 1 dose: 8 to 12 mg).

Day 2 onwards : Titrate rapidly to a standard maintenance target dose of 16 to 24 mg daily (single daily dose or split twice daily). Doses above 24 mg daily provide minimal additional receptor saturation (receptor occupancy exceeds 90% at 16–24 mg) and are rarely indicated.

B. Low-Dose Buprenorphine Induction ("Micro-Dosing" / The Bernese Method)

In the synthetic fentanyl era, standard induction frequently triggers severe precipitated withdrawal or is rejected by patients who cannot tolerate reaching a COWS ≥ 8 − 12 \ge 8-12 ≥ 8 − 12 . Low-dose induction introduces micro-doses of buprenorphine that slowly displace full agonists without precipitating acute withdrawal, while the patient continues taking their full-agonist opioid :

Day 1 : Buprenorphine 0.5 mg sublingual once daily; full-agonist continued as usual.

Day 2 : Buprenorphine 0.5 mg BID; full-agonist continued.

Day 3 : Buprenorphine 1 mg BID; full-agonist continued.

Day 4 : Buprenorphine 2 mg BID; full-agonist continued.

Day 5 : Buprenorphine 4 mg BID; full-agonist continued.

Day 6 : Buprenorphine 8 mg BID (16 mg/day); full-agonist continued.

Day 7 : Buprenorphine 16 mg daily; DISCONTINUE FULL-AGONIST OPIOID ENTIRELY .

2. Methadone Maintenance Therapy

Pharmacology : Methadone is a synthetic, long-acting full mu-opioid receptor agonist with high oral bioavailability and a variable elimination half-life ranging from 24 to 36 hours (up to 60 hours in some individuals). It provides potent receptor stimulation, completely relieving cravings and preventing withdrawal.

Federal Regulatory Framework (42 CFR Part 8) : In the United States, outpatient methadone for the treatment of opioid use disorder CANNOT be prescribed by an office-based clinician or dispensed by a retail community pharmacy . It can be dispensed exclusively through federally certified and SAMHSA-regulated Opioid Treatment Programs (OTPs) under directly observed daily dosing protocols (with patients earning take-home doses based on stability and negative toxicology screens).

Cardiovascular Toxicity & ECG Monitoring :

Methadone blocks cardiac human ether-à-go-go-related gene (hERG) potassium channels, producing dose-dependent prolongation of the corrected QT (QTc) interval and predisposing patients to life-threatening Torsades de Pointes .

Clinical Guidelines : Obtain a baseline ECG prior to methadone initiation. Repeat ECG at dose titration exceeding 100 mg/day 100\text{ mg/day} 100 mg/day , or if patient has syncope, unheralded palpitations, or concurrent QT-prolonging medications (e.g., citalopram, azole antifungals, fluoroquinolones). If QTc is > 500 ms >500\text{ ms} > 500 ms , reduce methadone dose or transition to buprenorphine.

Cytochrome P450 Drug Interactions : Methadone is extensively metabolized in the liver via CYP3A4, CYP2B6, and CYP2C19 .

CYP Inducers (rifampin, carbamazepine, phenytoin, efavirenz): Dramatically increase methadone clearance, precipitating severe withdrawal.

CYP Inhibitors (fluconazole, clarithromycin, fluoxetine): Decrease clearance, triggering methadone accumulation and fatal overdose.

3. Extended-Release Injectable Naltrexone (Vivitrol)

Pharmacology : Pure mu-opioid receptor antagonist administered as an intramuscular depot injection (380 mg) in the gluteal muscle every 4 weeks. Completely blocks opioid receptors, preventing any euphoric or analgesic response to exogenous opioids.

The Obligate Washout Period : Administering naltrexone to a patient with active opioids in their system precipitates instantaneous, catastrophic withdrawal. Initiation requires:

Strict abstinence from short-acting opioids for at least 7 to 10 days .

Strict abstinence from long-acting opioids (methadone, buprenorphine) for at least 10 to 14 days .

Objective confirmation with a negative urine drug screen .

Performance of a Naloxone Challenge Test (0.4 to 0.8 mg IV or SC naloxone; verify no withdrawal signs for 30–60 minutes before administering depot naltrexone).

Fatal Overdose Risk Upon Lapse : Chronic naltrexone therapy resets opioid tolerance to baseline (downregulating and resensitizing mu-opioid receptors). If a patient stops taking Vivitrol or attempts to override the receptor blockade by injecting massive doses of opioids, they are at catastrophic risk of fatal respiratory arrest from doses they previously tolerated.

Harm Reduction Frameworks & Overdose Prevention

Harm reduction encompasses evidence-based public health interventions designed to minimize the negative health, social, and legal consequences of drug use without mandating abstinence as a prerequisite.

1. Naloxone (Narcan) Overdose Rescue

Mechanism : Pure, competitive mu-opioid receptor antagonist with high affinity that displaces opioids from receptors, rapidly reversing respiratory depression within 2 to 3 minutes.

Formulations : Naloxone 4 mg intranasal spray (single pre-packaged device sprayed into one nostril; OTC status). Intramuscular autoinjector or 0.4 mg/mL vial for IM/SC injection.

Administration Protocol : If an unresponsive individual exhibits signs of opioid overdose (pinpoint pupils, respiratory rate < 8 − 10 breaths/min <8-10\text{ breaths/min} < 8 − 10 breaths/min , cyanosis, snoring/gurgling respirations):

Administer one 4 mg spray into one nostril.

Call 911 immediately.

If no response or inadequate spontaneous ventilation occurs after 2 to 3 minutes , administer a second 4 mg spray in the opposite nostril.

The Half-Life Mismatch & Re-Narcotization :

Naloxone has an elimination half-life of 30 to 90 minutes .

Many synthetic opioids (fentanyl depots, methadone, extended-release oxycodone) have durations of action lasting 12 to 36 hours.

When naloxone wears off, residual circulating opioids can rebound onto receptors, causing re-narcotization and recurrent fatal respiratory depression . All patients revived with naloxone must be transported to an emergency department and observed for a minimum of 2 to 4 hours.

Universal Co-Prescribing Guidelines : Clinicians must co-prescribe naloxone to:

All patients with a diagnosed opioid use disorder.

Any patient receiving chronic prescription opioid therapy at doses ≥ 50 Morphine Milligram Equivalents (MME)/day \ge 50\text{ Morphine Milligram Equivalents (MME)/day} ≥ 50 Morphine Milligram Equivalents (MME)/day .

Any patient receiving concomitant opioids and central nervous system depressants (e.g., benzodiazepines, z-drugs, gabapentinoids, sedating muscle relaxants).

Patients with past history of overdose, substance use treatment, or comorbid pulmonary/hepatic/renal disease.

2. Syringe Services Programs & Fentanyl Test Strips

Syringe Services Programs (SSPs) : Community-based programs providing access to sterile needles/syringes, safe disposal containers, and vaccination. SSPs reduce HIV and HCV incidence by over 50% and increase linkage to addiction treatment five-fold without increasing community crime or drug use rates.

Fentanyl Test Strips (FTS) : Lateral flow chromatographic strips that detect fentanyl and major analogues in drug samples dissolved in water, allowing individuals to identify contaminated supplies and adjust consumption behavior.

Xylazine ("Tranq") Awareness : An alpha-2 adrenergic agonist approved exclusively for veterinary sedation that is increasingly co-adulterated into illicit synthetic fentanyl supplies.

Induces profound sedation, bradycardia, hypotension, and horrific necrotic skin ulcerations that appear at sites distant from injection points.

Critical Pearl : Xylazine is not an opioid; it is NOT reversed by naloxone ! However, in any suspected overdose, naloxone must still be administered immediately to reverse the fentanyl component, followed by supportive airway and circulatory management.

• Stimulant Use Disorders: Cocaine & Methamphetamine
• Neurobiology & Systemic Complications

Cocaine : Alkaloid that competitively blocks presynaptic reuptake transporters for dopamine (DAT), norepinephrine (NET), and serotonin (SERT), producing profound synaptic monoamine accumulation. Also blocks voltage-gated sodium channels, conferring local anesthetic effects and arrhythmogenic cardiotoxicity.

Methamphetamine : Synthetic phenylisopropylamine with potent, durable neurotoxicity. Unlike cocaine, methamphetamine not only blocks monoamine reuptake but also reverses vesicular monoamine transporter 2 (VMAT2) and DAT, actively pumping massive quantities of dopamine from storage vesicles directly into the synaptic cleft.

Clinical Manifestations :

Neuropsychiatric : Intense euphoria followed by chronic paranoia, persecutory delusions, auditory/visual hallucinations, aggressive psychomotor agitation, and formication ("meth bugs") —delusional parasitosis causing severe, chronic skin-picking and infected neurotic excoriations.

Cardiovascular : Severe hyperadrenergic surges causing coronary vasospasm, accelerated atherosclerosis, acute myocardial infarction, aortic dissection, malignant hypertension, intracerebral hemorrhage, and dilated hyperadrenergic cardiomyopathy .

Oral Pathology ("Meth Mouth") : Rampant, severe dental caries, enamel erosion, and tooth loss. Caused by a confluence of drug-induced salivary gland hypoperfusion (severe xerostomia), prolonged bruxism/jaw-clenching, consumption of sugary beverages, and complete neglect of oral hygiene.

Evidence-Based Management of Stimulant Use Disorders

Unlike opioid use disorder, there are NO FDA-APPROVED MEDICATIONS for cocaine or methamphetamine use disorder.

Contingency Management (CM) : The undisputed gold standard treatment with the largest effect size in addiction medicine.

Rooted in operant conditioning: Patients earn immediate, tangible, escalating incentives (vouchers, gift cards, prize draws) contingent upon objective biological verification of drug abstinence (confirmed drug-negative urine screens).

Highly effective at inducing and sustaining stimulant abstinence and retaining patients in behavioral care.

Community Reinforcement Approach (CRA) & CBT : Structured counseling identifying behavioral reinforcers in the patient's family, employment, and social environment to build an attractive drug-free lifestyle.

Emerging Pharmacotherapy (The ADAPT-2 Trial) :

The landmark ADAPT-2 randomized trial evaluated combination pharmacotherapy for moderate-to-severe methamphetamine use disorder:

Oral Bupropion XL 450 mg daily (dopamine/norepinephrine reuptake inhibitor that dampens withdrawal dysphoria and craving) PLUS Intramuscular Extended-Release Naltrexone 380 mg every 3 weeks (modulates endogenous opioid tone regulating dopamine release in the VTA).

Demonstrated modest but statistically significant improvements in verified methamphetamine-negative urine screens compared to placebo (13.6% vs 2.5%; number needed to treat [NNT] = 9). Currently used off-label in specialized addiction clinics.

Loading diagram... MOUD Decision Tree and Buprenorphine Induction Algorithm