Medical terms, defined.

Pediculosis is infestation by blood-feeding lice: Pediculus humanus capitis (head), Pediculus humanus corporis (body), or Pthirus pubis (pubic/"crab" lice). It causes intense pruritus from a hypersensitivity reaction to louse saliva and...

Lisinopril is an ACE inhibitor used for hypertension, heart failure, post-MI remodeling prevention, and diabetic nephropathy. It blocks conversion of angiotensin I to angiotensin II and decreases bradykinin breakdown, causing vasodilatio...

Allergic contact dermatitis (ACD) is a Type IV (delayed-type, T-cell mediated) hypersensitivity reaction of the skin to a hapten after prior sensitization. It presents 48–72 hours after re-exposure as a pruritic, erythematous, eczematous...

Enalapril is an ACE inhibitor prodrug (converted in the liver to enalaprilat) that blocks conversion of angiotensin I to angiotensin II, lowering BP and reducing cardiac remodeling. Used for hypertension, HFrEF, post-MI, and diabetic nep...

Losartan is an angiotensin II receptor blocker (ARB) that selectively blocks the AT1 receptor, causing vasodilation and decreased aldosterone secretion. It is used for hypertension, diabetic nephropathy, and heart failure (especially in...

Captopril is a short-acting, sulfhydryl-containing ACE inhibitor used for hypertension, heart failure, post-MI remodeling prevention, and diabetic nephropathy. It blocks conversion of angiotensin I to angiotensin II and prevents bradykin...

Lansoprazole is a proton pump inhibitor (PPI) that irreversibly inhibits the H+/K+ ATPase on gastric parietal cells, suppressing gastric acid secretion. It is used for GERD, peptic ulcer disease, H. pylori eradication (in combination reg...

Ticagrelor (Brilinta) is an oral, reversible, direct-acting P2Y12 ADP-receptor antagonist used with aspirin for dual antiplatelet therapy in acute coronary syndrome (ACS) and after PCI. Unlike clopidogrel, it is not a prodrug, so it does...

Simvastatin is an HMG-CoA reductase inhibitor (statin) that lowers LDL cholesterol by blocking the rate-limiting step of hepatic cholesterol synthesis. It is a lipophilic prodrug (lactone) metabolized by CYP3A4, so it has many drug inter...

Pantoprazole is a proton pump inhibitor (PPI) that irreversibly inhibits the H+/K+ ATPase on gastric parietal cells, markedly reducing gastric acid secretion. It is used for GERD, peptic ulcer disease, Zollinger-Ellison syndrome, erosive...

Prednisolone is the active metabolite of prednisone: an intermediate-acting synthetic glucocorticoid (about 4x the potency of hydrocortisone, minimal mineralocorticoid activity). It's used for its anti-inflammatory and immunosuppressive...

Naproxen is a nonselective COX-1/COX-2 inhibitor NSAID (propionic acid derivative) used for pain, inflammation, fever, dysmenorrhea, gout, and arthritis. It has a longer half-life (~12-17 h) than ibuprofen, allowing BID dosing. Key toxic...

Minocycline is a second-generation, lipophilic tetracycline antibiotic that inhibits the bacterial 30S ribosomal subunit (blocks aminoacyl-tRNA binding at the A site). It is used for acne, MRSA skin infections, rickettsial and chlamydial...

Sumatriptan is a selective 5-HT1B/1D receptor agonist used as abortive therapy for acute migraine and cluster headache. It causes cranial vessel vasoconstriction and inhibits release of CGRP and substance P from trigeminal nerve terminal...

Oxycodone is a semisynthetic opioid (derived from thebaine) that acts as a full agonist at the mu-opioid receptor. It is used for moderate-to-severe pain. Key toxicity is respiratory depression, with miosis and CNS depression. Overdose i...

Fluoxetine (Prozac) is a selective serotonin reuptake inhibitor (SSRI) used first-line for major depressive disorder, OCD, bulimia nervosa, panic disorder, and PMDD. It has the longest half-life of the SSRIs (active metabolite norfluoxet...

Sertraline is a selective serotonin reuptake inhibitor (SSRI) and first-line agent for major depressive disorder, OCD, PTSD, panic disorder, social anxiety disorder, and PMDD. It blocks the presynaptic serotonin transporter (SERT), incre...

Citalopram is a selective serotonin reuptake inhibitor (SSRI) used first-line for major depressive disorder and anxiety disorders. Its high-yield toxicity is dose-dependent QT prolongation (max 40 mg/day; 20 mg/day if age >60, hepatic im...

Hydrocodone is a semisynthetic opioid agonist (primarily mu-receptor) derived from codeine, used for moderate to severe pain and as an antitussive. It is usually combined with acetaminophen (e.g., Vicodin, Norco), so overdose risks inclu...

Escitalopram is the S-enantiomer of citalopram and a selective serotonin reuptake inhibitor (SSRI) used first-line for major depressive disorder and generalized anxiety disorder. It blocks the presynaptic serotonin transporter (SERT), in...

Duloxetine is a serotonin-norepinephrine reuptake inhibitor (SNRI) used for major depressive disorder, generalized anxiety disorder, diabetic peripheral neuropathic pain, fibromyalgia, and chronic musculoskeletal pain. It is also approve...

Olanzapine is a second-generation (atypical) antipsychotic that antagonizes D2 and 5-HT2A receptors (with strong H1, M1, and α1 blockade). It is used for schizophrenia, bipolar mania, and agitation. It has a high risk of metabolic side e...

Venlafaxine is a serotonin-norepinephrine reuptake inhibitor (SNRI) used for major depressive disorder, generalized anxiety disorder, social anxiety disorder, panic disorder, and (off-label) neuropathic pain and vasomotor symptoms. At hi...

Memantine is a noncompetitive, low-to-moderate affinity, uncompetitive open-channel NMDA receptor antagonist used for moderate-to-severe Alzheimer disease dementia. It blocks pathologic glutamate-mediated excitotoxicity (Ca2+ influx) whi...

Nortriptyline is a secondary-amine tricyclic antidepressant (TCA) and the active metabolite of amitriptyline. It inhibits reuptake of norepinephrine (more than serotonin). It is used for depression, neuropathic pain, migraine prophylaxis...

Alprazolam (Xanax) is a short-to-intermediate-acting benzodiazepine that positively modulates GABA-A receptors, increasing the FREQUENCY of chloride channel opening. It is used for generalized anxiety disorder, panic disorder, and acute...

Zolpidem (Ambien) is a non-benzodiazepine "Z-drug" hypnotic that selectively binds the BZ1 (omega-1) site on the GABA-A receptor (alpha-1 subunit), increasing the frequency of chloride channel opening. It is used for short-term treatment...

Diazepam is a long-acting benzodiazepine that positively modulates GABA-A receptors, increasing the FREQUENCY of chloride channel opening. It is used for anxiety, status epilepticus, alcohol withdrawal, muscle spasm, and preoperative sed...

Clostridioides (Clostridium) difficile is a gram-positive, spore-forming, obligate anaerobic bacillus and the leading cause of antibiotic-associated diarrhea and pseudomembranous colitis. It is triggered by disruption of normal gut flora...

EBV (Epstein-Barr virus, HHV-4) is a double-stranded DNA gammaherpesvirus that infects B cells via CD21 (CR2). It causes infectious mononucleosis (fever, pharyngitis, lymphadenopathy, atypical lymphocytes) and is associated with Burkitt...

GBS is most commonly Guillain-Barré Syndrome, an acute post-infectious autoimmune demyelinating polyneuropathy that causes ascending symmetric weakness with areflexia. On boards, GBS can also mean Group B Streptococcus (S. agalactiae), t...

GAS most commonly = Group A Streptococcus (Streptococcus pyogenes), a gram-positive, beta-hemolytic, bacitracin-sensitive, PYR-positive coccus in chains. It causes pharyngitis, impetigo, erysipelas, cellulitis, necrotizing fasciitis, sca...

Human herpesvirus 8 (HHV-8), also called Kaposi sarcoma-associated herpesvirus (KSHV), is a double-stranded DNA gammaherpesvirus that causes Kaposi sarcoma (KS), primary effusion lymphoma, and multicentric Castleman disease. It is most c...

Strongyloides stercoralis is a soil-transmitted nematode (roundworm) whose filariform larvae penetrate skin (usually of the feet) and cause intestinal infection with diarrhea, abdominal pain, and a migratory serpiginous rash (larva curre...

Human herpesvirus 6 (HHV-6A and HHV-6B) is a dsDNA betaherpesvirus; HHV-6B causes roseola infantum (exanthem subitum): high fever for 3-5 days in an infant (6-24 months) that resolves just as a diffuse maculopapular rash appears. Complic...

Hepatitis D (HDV, delta agent) is a defective circular negative-sense ssRNA virus that requires HBsAg from hepatitis B virus to assemble and infect, so it occurs only as coinfection or superinfection with HBV. Superinfection in a chronic...

Respiratory syncytial virus (RSV) is an enveloped, negative-sense, single-stranded RNA virus (Paramyxoviridae family, Orthopneumovirus genus) and the leading cause of bronchiolitis and lower respiratory tract infection in infants <2 year...

Influenza virus is an enveloped, segmented, negative-sense single-stranded RNA virus (Orthomyxoviridae) that causes acute febrile respiratory illness. Hemagglutinin (HA) mediates attachment and neuraminidase (NA) mediates release; antige...

A prion is an infectious, misfolded protein (PrP^Sc, rich in beta-pleated sheets) that lacks nucleic acid and causes transmissible spongiform encephalopathies by inducing normal cellular prion protein (PrP^C, mostly alpha-helical) to mis...

Diabetic dermopathy ("shin spots") is the most common cutaneous manifestation of diabetes mellitus. It presents as asymptomatic, atrophic, hyperpigmented, round-to-oval brown papules and plaques on the pretibial (shin) areas. It requires...

Diabetic peripheral neuropathy (DPN) is the most common complication of diabetes mellitus, typically presenting as a symmetric, distal, length-dependent "stocking-glove" sensory polyneuropathy. It results from chronic hyperglycemia-induc...

Diabetic foot refers to foot pathology in diabetes mellitus caused by the triad of peripheral neuropathy, peripheral arterial disease (PAD), and infection/impaired immunity. It presents with painless neuropathic ulcers, Charcot arthropat...

HIV is an enveloped, positive-sense single-stranded RNA retrovirus (genus Lentivirus) that infects CD4+ T cells, macrophages, and dendritic cells, causing progressive immunodeficiency and AIDS if untreated. It uses reverse transcriptase...

Diabetic polyneuropathy (distal symmetric sensorimotor polyneuropathy) is the most common chronic complication of diabetes, causing a length-dependent "stocking-glove" loss of sensation, paresthesias, and neuropathic pain. It results fro...

Diabetic cardiomyopathy is myocardial disease occurring in diabetic patients that is independent of coronary artery disease, hypertension, or valvular disease. It begins with diastolic dysfunction (HFpEF phenotype) and may progress to sy...

Diabetic macular edema (DME) is fluid accumulation and thickening of the macula due to breakdown of the blood-retinal barrier from chronic hyperglycemia-induced microvascular damage. It is the leading cause of vision loss in patients wit...

A diabetic foot ulcer (DFU) is a full-thickness skin defect, typically on the plantar surface of the foot (e.g., metatarsal heads), caused by the combination of peripheral neuropathy, peripheral arterial disease, and repetitive unrecogni...

Diabetic gastroparesis is delayed gastric emptying without mechanical obstruction, caused by long-standing diabetes (autonomic neuropathy of the vagus nerve, loss of interstitial cells of Cajal, and hyperglycemia). It presents with early...

Autonomic dysreflexia is a life-threatening sympathetic overreaction in patients with spinal cord injury at or above T6. A noxious stimulus below the lesion (classically bladder distension or fecal impaction) triggers uncontrolled sympat...

Autonomic dysfunction (dysautonomia) is impaired function of the sympathetic and/or parasympathetic nervous system, causing abnormal control of BP, HR, GI/GU function, sweating, and pupils. Classic presentation is orthostatic hypotension...