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Antiandrogen
An antiandrogen, also called an androgen antagonist or androgen blocker, is a drug that stops androgens like testosterone from binding their receptors, used mainly against prostate cancer.
Antiarrhythmic agent
Antiarrhythmic agents are drugs for abnormal heart rhythms, grouped by the Vaughan Williams classes I–IV (sodium channel, beta-blocker, potassium channel, calcium channel blockers), extended in 2018 with classes 0 and V–VII; CAST showed class Ic drugs raise post-infarction mortality.
Antibacterial photodynamic therapy
Antibacterial photodynamic therapy (aPDT), also called photodynamic inactivation or PACT, uses a light-activated photosensitizer to generate reactive oxygen species that kill bacteria, mainly for oral and skin infections.
Antibiogram
An antibiogram is a periodic, cumulative summary of antimicrobial susceptibility testing results from a defined patient population, guiding empirical antibiotic therapy before individual susceptibility results are available.
Antibiotic
Antibiotic: drugs that kill bacteria or stop their spread; ineffective against viruses. First was penicillin, discovered by Fleming in 1928; six main classes; resistance now affects 1 in 6 infections.
Antibiotic Prophylaxis
Antibiotic prophylaxis, also called antimicrobial or surgical prophylaxis, is preventive antibiotic use before procedures. Key facts: timed pre-incision dosing, single-dose courses, narrowed endocarditis indications.
Antibiotic resistant Neisseria gonorrhoeae
Antibiotic resistant Neisseria gonorrhoeae, or drug-resistant gonorrhoea (super gonorrhoea), strains resistant to all gonorrhoea antibiotic classes; ceftriaxone is the last first-line drug, with penA 60.001-mediated resistance spreading globally.
Antibody test
An antibody test, also called a serological test, is a blood test that detects antibodies against a pathogen or antigen to show prior infection, immune response, or vaccination status.
Antibody-dependent complement deposition assay
The antibody-dependent complement deposition (ADCD) assay is a bead-based flow cytometry serology assay that quantifies complement proteins deposited by antibodies in serum or plasma, reported in 2019.
Antibody-directed enzyme prodrug therapy
Antibody-directed enzyme prodrug therapy (ADEPT) is a two-step cancer treatment in which an antibody-enzyme conjugate targets tumor cells, activating a nontoxic prodrug into a cytotoxic drug at the tumor site.
Anticholinergic
Anticholinergic drugs competitively block acetylcholine at muscarinic receptors; over 600 medications have anticholinergic activity. Key issues are anticholinergic burden scales, cognitive adverse effects, possible dementia risk, and toxicity treated with physostigmine.
Anticitrullinated protein antibody negative
Anticitrullinated protein antibody negative (ACPA-negative, ICD-11 MA14.11): absence of detectable anti-CCP antibodies in serum. A negative test does not rule out rheumatoid arthritis; with negative rheumatoid factor it defines seronegative RA.
Anticitrullinated protein antibody positive
ACPA positive (anti-CCP positive): blood autoantibodies against citrullinated peptides, strongly associated with rheumatoid arthritis; pooled sensitivity 67%, specificity 95%, detectable years before RA onset, also positive in some other diseases.
Anticoagulant
Anticoagulant drugs (warfarin, heparins, DOACs apixaban, rivaroxaban, edoxaban, dabigatran) inhibit coagulation factors to prevent and treat VTE and atrial fibrillation stroke; includes INR targets, reversal agents, and andexanet alfa's 2025 withdrawal.
Anticoagulation Bridge
Anticoagulation bridge (bridging anticoagulation, heparin bridging): temporary UFH or LMWH given while warfarin or a DOAC is interrupted for surgery. Trials show added bleeding without fewer clots; guidelines restrict it to highest-risk patients.
Anticoagulation reversal
Anticoagulation reversal is the use of specific antidotes and blood products to counteract anticoagulant drugs in major bleeding or before urgent surgery, using agents like idarucizumab and 4F-PCC.
Anticonvulsant
Anticonvulsants, also called antiseizure medications or antiepileptic drugs, treat seizures by controlling abnormal brain electrical activity; about 30 exist, controlling seizures in roughly 70% of people with epilepsy, with uses beyond epilepsy including migraine and neuropathic pain.
Antidepressant
Antidepressants are prescription medicines, mainly SSRIs, SNRIs, NDRIs, TCAs, and MAOIs, used to treat depression and also anxiety, pain, and insomnia; they take 4 to 8 weeks to work and all beat placebo in a 2018 meta-analysis of 522 trials.
Antidepressant discontinuation syndrome
Antidepressant discontinuation syndrome, also called antidepressant withdrawal, causes dizziness, brain zaps, insomnia and flu-like symptoms 36–96 hours after stopping SSRIs, SNRIs, TCAs, or MAOIs; roughly 15% placebo-attributable incidence, worst with paroxetine and venlafaxine, managed by slow hyperbolic tapering per NICE 2023.
Antidote
An antidote is an agent that counteracts a poison by neutralizing it chemically, competing at receptors, or speeding elimination. Examples include naloxone for opioids, atropine, and activated charcoal.
Antiemetic
Antiemetic: drug class preventing or treating nausea and vomiting. Includes 5-HT3 antagonists (ondansetron), dopamine antagonists (metoclopramide), NK1 antagonists, antihistamines, steroids; used in chemotherapy, surgery, pregnancy, gastroenteritis.
Antifungal
Antifungals are antimicrobial drugs (azoles, echinocandins, polyenes, terbinafine, flucytosine, ibrexafungerp) that target fungal ergosterol, its synthesis, or the cell wall. Only three main classes treat invasive infections, and resistance is rising.
Antifungal susceptibility testing
Antifungal susceptibility testing (AFST) is a clinical microbiology laboratory method measuring how well antifungal drugs inhibit patient fungal isolates, usually reported as a minimum inhibitory concentration.
Antigen bead assay
An antigen bead assay is a multiplex immunoassay in which antigens are coupled to color-coded microspheres to detect and semi-quantify antibodies in serum, chiefly anti-HLA antibodies.
Antigen test
An antigen test is a rapid diagnostic test that detects viral proteins in nasal swabs, giving results in 10 to 30 minutes at home or point of care.
Antihemophilic factor, pegylated (mw 20000) human sequence recombinant
Antihemophilic factor, pegylated (mw 20000) human sequence recombinant is rurioctocog alfa pegol (Adynovate/Adynovi), a 20-kDa branched-PEG B-domain PEGylated full-length recombinant factor VIII for hemophilia A, approved 2015, half-life 1.4-1.5x its parent Advate.
Antihemorrhagic
Antihemorrhagic agents (hemostatics, antifibrinolytics such as tranexamic acid) are drugs, factor concentrates, and dressings that stop bleeding; TXA cuts trauma mortality by 10% if given within three hours.
Antihistamine
An antihistamine, also called a histamine antagonist, is a drug that counteracts histamine during allergic reactions, used for rhinitis, urticaria, conjunctivitis, and itching; second-generation drugs are preferred.
Antihypertensive and Lipid Lowering Treatment to Prevent Heart Attack Trial
The Antihypertensive and Lipid Lowering Treatment to Prevent Heart Attack Trial (ALLHAT) was a major US National Heart, Lung, and Blood Institute trial testing newer blood pressure drugs against a diuretic from 1994.
Antimicrobial
Antimicrobial: umbrella term for agents killing or inhibiting microbes, covering antibiotics, antifungals, antivirals, and antiparasitics; distinguished from the narrower term antibiotic, with global resistance tracked by WHO GLASS.