Opioid use disorder

Opioid withdrawal is the autonomic, secretory, and gastrointestinal syndrome (piloerection, lacrimation, rhinorrhea, yawning, mydriasis, myalgias, diarrhea) that follows cessation, dose reduction, or antagonist reversal of opioid use, beginning within hours for short-acting opioids but taking days for long-acting agents such as methadone. Diagnosis is clinical. First-line treatment is an opioid agonist, methadone or buprenorphine, with clonidine and symptom-targeted agents added for residual symptoms.

Alcohol use disorder is a chronic pattern of drinking meeting 2 or more of 11 DSM-5 criteria within a 1-year period, screened with the CAGE or AUDIT-C and confirmed by history. First-line management combines a brief behavioral intervention and cognitive behavioral therapy with naltrexone or acamprosate, reserving disulfiram for highly motivated patients who can maintain abstinence.

A pattern of benzodiazepine use marked by impaired control, continued use despite harm, tolerance, and withdrawal, most often beginning with a prescription for anxiety or insomnia continued past its intended short course; management is a sequenced deprescribing taper after converting to a long-acting agent, paired with a non-benzodiazepine treatment of the underlying disorder.

Stimulant use disorder is a pattern of amphetamine-type stimulant use, covering methamphetamine, misused prescription amphetamines, and MDMA, that meets 2 or more of 11 substance use disorder criteria within 12 months. Intoxication produces a sympathomimetic toxidrome with hyperthermia and agitation; management starts with a benzodiazepine and active cooling, since no pharmacotherapy is approved for the use disorder itself and contingency management is the named behavioral treatment.

Cocaine use disorder is a pattern of cocaine use causing significant impairment or distress, distinct from acute intoxication, diagnosed when a patient meets at least 2 of 11 DSM-5 substance use criteria within 12 months. Acute cocaine-associated chest pain is managed first with a benzodiazepine, then nitrates or a calcium channel blocker, while beta blockade is avoided because of concern for unopposed alpha stimulation; no medication is approved for the use disorder itself, so treatment rests on psychosocial care.

Tobacco (nicotine) use disorder is a pattern of compulsive tobacco or nicotine use meeting 2 or more of 11 substance-use-disorder criteria within a 12-month period, driven by nicotine's stimulation of central nicotinic acetylcholine receptors and marked by a withdrawal syndrome of irritability, anxiety, and craving on cessation. Diagnosis is clinical; first-line treatment combines behavioral counseling with varenicline or combination nicotine replacement therapy, started before a set quit date.

Hepatitis B virus is a bloodborne and sexually transmitted DNA virus that causes acute hepatitis and, when infection becomes chronic, progresses through immune-tolerant, immune-active, immune-control, and reactivation phases toward cirrhosis and hepatocellular carcinoma. Diagnosis rests on hepatitis B serology, chronic infection is treated with entecavir or tenofovir, and reactivation during immunosuppression is prevented with prophylactic antiviral therapy.

Hepatitis C virus is a bloodborne RNA virus, transmitted mainly by injection drug use, that produces mostly asymptomatic acute infection and chronic infection in 60% to 80% of cases. Diagnosis is by HCV antibody followed by HCV RNA, and direct-acting antiviral regimens cure more than 90% of patients, reducing but not eliminating the risk of cirrhosis and hepatocellular carcinoma.

Infective endocarditis is microbial infection of the endocardium, usually a heart valve, producing vegetations that cause valve destruction, embolism, and systemic infection. Diagnosis uses the modified Duke criteria combining blood cultures and echocardiography, and treatment is prolonged targeted intravenous antibiotics with surgery for complications.

A skin abscess is a purulent, fluctuant collection within the dermis and subcutaneous fat, usually caused by Staphylococcus aureus including MRSA, whose primary treatment is incision and drainage, with antibiotics reserved as an adjunct by size and systemic signs.

Acute HIV infection, also called the acute retroviral syndrome, is the symptomatic viremic phase in the days to weeks after HIV acquisition, presenting with fever, fatigue, myalgia, rash, and pharyngitis at a time when antibody testing may still be negative. Diagnosis requires an HIV RNA viral load, and antiretroviral therapy should begin as soon as the patient is ready, regardless of CD4 count.

Major depressive disorder is a mood disorder defined by 5 or more of 9 major depressive episode symptoms, including depressed mood or anhedonia, present nearly every day for at least 2 weeks and causing significant functional impairment. Diagnosis is clinical, screened with the Patient Health Questionnaire. First-line treatment is cognitive behavioral therapy, a selective serotonin reuptake inhibitor (SSRI) such as sertraline, or both, escalating to augmentation, esketamine, or electroconvulsive therapy for refractory or acutely suicidal presentations.