[L. agere, to do]
Someone or something that causes an effect. For example, bacteria that cause disease are agents of the specific diseases they cause, and medicine is a therapeutic agent.

adrenergic neuron-blocking agent

Any agent that inhibits transmission of sympathetic nerve stimuli regardless of whether alpha- or beta-adrenergic receptors are involved.
SEE: alpha-adrenergic receptor; SEE: beta-adrenergic receptor

alkylating agent

Any agent that introduces an alkyl radical into a compound in place of a hydrogen atom. Alkylating agents are used to treat cancer because they interfere with cell metabolism and growth. Examples include cis-platinum and cyclophosphamide.

alpha-adrenergic blocking agent

A medication that interferes with excitatory sympathetic nervous system stimuli. Agents from this class are used to treat hypertension, prostatic hyperplasia, and kidney stones.
SYN: SEE: alpha blocker
SEE: beta-adrenergic blocking agent

anabolic agent

Any of a class of steroid hormones resembling testosterone. These agents stimulate the growth or manufacture of body tissues. They have been used, sometimes in high doses, by male and female athletes to improve performance. This use has been judged to be illegal by a number of organizations that supervise sports, including the International Olympic Committee and the U.S. Olympic Committee. These agents are also used to treat patients with wasting illnesses.
SEE: doping; SEE: ergonomic aid
Descriptive text is not available for this imageIndiscriminate use of anabolic agents is inadvisable because of the undesirable side effects they may produce, e.g., in women, hirsutism, masculinization, and clitoral hypertrophy; in men, aggressiveness and testicular atrophy.

antianxiety agent

SEE: Anxiolytic.

antiulcer agent

A drug to prevent or treat ulcers of the stomach or small intestine.

beta-adrenergic agent

A synthetic or natural drug that stimulates beta (sympathetic) receptors, e.g., epinephrine and norepinephrine.

beta-adrenergic blocking agent

Any drug that inhibits the activity of the sympathetic nervous system and of adrenergic hormones.
Members of this class of drugs are used to treat hypertension, angina pectoris, myocardial infarction, aortic dissection, arrhythmias, glaucoma, and other conditions. Commonly prescribed beta blockers include atenolol, carvedilol, metoprolol, nadolol, propranolol, and pindolol.
SYN: SEE: beta blocker

Descriptive text is not available for this imageSide effects of beta blockers include worsening of asthma, blunting of the cardiovascular symptoms of hypoglycemia, bradycardia, and heart block. Rapid withdrawal from a beta-blocking drug by a patient accustomed to its use may produce tachycardia or other arrhythmias, rebound hypertension, or myocardial ischemia or infarction.

binding agent

Any agent used to form dusty or powdery medicines into pills.

blister agent

A vesicant, esp. any such agent (like mustard gas) used in chemical warfare.

buffering agent

SEE: Buffer.

bypassing agent

A drug used to treat a condition indirectly. In hemophilia, for example, it is any drug used instead of directly replacing missing or antibody-inactivated clotting factors.

CBRNE agent

Any chemical, biological, radiologic, nuclear, or explosive agent that may be used as a weapon in military or terrorist activities.

ceruminolytic agent

An agent that dissolves cerumen in the external ear canal. Obstruction of the ear canal with cerumen can cause itching, pain, and temporary conductive hearing loss. The first approach to treatment should be removal of the obstruction manually with a blunt curet or loop or by irrigation. Cerumen solvents are not always recommended because they often do not eliminate the problem and frequently cause maceration of the skin of the canal and allergic reactions.

cervical-ripening agent

Any agent that promotes dilation of the cervix in anticipation of childbirth.

chaotropic agent

An ion that disrupts membranes, nucleic acids, and proteins.

chelating agent

SEE: Chelator.

cholinergic blocking agent

SEE: Anticholinergic (2).

clearing agent

1. An agent that increases the transparency of tissues prepared for microscopic examination.
2. In radiographic film processing, the active agent in the fixer that clears undeveloped silver bromide crystals from the film. The most common agent is ammonium thiosulfate.
SYN: SEE: fixing agent

colon-cleansing agent

An agent to force the bowels to evacuate, e.g., in preparation for colonoscopy.

cytotoxic agent

An agent that destroys cells or prevents them from multiplying. Cytotoxic agents are used to treat cancers and severe immunological disorders, e.g., vasculitis and some forms of glomerulonephritis. An ideal agent would destroy proliferating cells without injuring the normal cells of the body.

differentiating agent

An agent such as all-trans-retinoic acid, used in differentiation therapy.

disclosing agent

A diagnostic aid used in dentistry to stain areas of the teeth that are not being cleaned adequately. A dye such as erythrosine sodium is used to color dental plaque so that inadequately brushed surfaces can be shown to patients.

Eaton agent

SEE: Eaton agent

erythropoiesis-stimulating agent

ABBR: ESA Any drug that binds to cellular receptors for erythropoietin and encourages red blood cell production by the bone marrow. Members of this class of drugs, which include epoietin and darbopoietin, are used to treat anemia, e.g., in patients with chronic kidney disease, cancer, or aplastic anemia. ESAs are used as an alternative to red blood cell transfusions. Potential side effects of treatment include high blood pressure and an increased risk of blood clots.

filling agent

SEE: Filler.

fixing agent

SEE: clearing agent

health care agent

SEE: Health care proxy (2).

immunobiological agent

SEE: Immunobiological.

immunosuppressive agent

SEE: immunosuppressant.

luting agent

SEE: Cementation.

nasal drying agent

Any anticholinergic, antihistaminic, or drug of a related class that decreases watery discharge from the nose, e.g., in rhinitis.

nerve agent

A cholinesterase inhibitor used in biological warfare, such as sarin or VX. Antidotes include atropine or pralidoxime.

Norwalk agent

SEE: virus

ocular hypotensive agent

A drug that reduces intraocular pressure, e.g., in glaucoma.

oral agent

Any medication that dissolves in the mouth, is chewed, or is swallowed, as opposed to medications given topically, by infusion, or by injection.

oral hypoglycemic agent

ABBR: OHA. Any drug taken by mouth that lowers or maintains blood glucose (as opposed to insulin, a drug taken parenterally to control blood sugar). In addition to diet and exercise regimens, OHAs are typically used to control blood glucose levels in type 2 diabetes mellitus. Commonly used oral agents for diabetes include metformin (a biguanide), sulfonylureas (such as glyburide), alpha-glucosidase inhibitors (acarbose), and thiazolidinediones (pioglitazone). Used appropriately, OHAs lower hemoglobin A1c levels by about 0.5 to 1.5%. SEE TABLE: Oral Agents That Lower Blood Glucose*
Oral Agents That Lower Blood Glucose*

Class of DrugActivityAdverse Features
Alpha-glucosidase inhibitors, e.g., acarboseDelay absorption of glucose from intestinal tractFlatulence and other abdominal side effects
Biguanides, e.g., metforminImprove sensitivity to insulin; decrease glucose production by the liverLess weight gain than with other agents; avoid in patients with renal failure
Sulfonylureas, 1st generation, e.g., tolazamideCause beta cells to release insulinResistance to drug may develop over time
Sulfonylureas, 2nd generation, e.g., glipizide, glyburide, othersSame as 1st generation; also increase sensitivity to insulinSame as 1st generation
Thiazolidinediones, e.g., pioglitazoneImprove sensitivity to insulin; improve lipid profileMonthly monitoring of liver functions needed for some drugs in this class due to risk of toxicity. Heart failure and other heart diseases.

progestational agent

SEE: Progestin (1).

radioprotective agent

Any substance that shields the body from damage by radioactivity.

reducing agent

A substance that loses electrons easily and therefore causes other substances to be reduced (such as hydrogen sulfide, sulfur dioxide).
SYN: SEE: reducing substance

reversal agent

1. A medication that blocks the action of a previously administered drug.
2. An antidote.

riot control agent

The formal term for any of those vaporized chemicals (such as chloroacetophenone and chlorobenzylidene malononitrile) used in tear gas. These agents cause irritation on contact, e.g., to the skin, eyes, or respiratory mucosa, and produce visual blurring, itching and burning of the skin, coughing, wheezing, nausea or vomiting, and occasionally asphyxia.

To reduce the effects of a tear gas exposure, remove the victim's clothes and wash the skin and hair promptly and thoroughly in soapy water. Rinse exposed eyes with sterile liquids. Patients who develop asthma or wheezing should be treated with bronchodilators such as albuterol.

sclerosing agent

A substance used to cause sclerosis, esp. of the lining of a vein.
SEE: varicose vein

surface-active agent

SEE: Surfactant.

thermal agent

Heat or cold used to promote healing.
SEE: physical agent modality

thrombolytic agent

Any drug that degrades blood clots. Examples include streptokinase, tenecteplase, tissue plasminogen activator, and urokinase. Such drugs are used to treat the abnormal blood clotting that occurs in heart attacks, some strokes, and pulmonary emboli. They are informally called “clot busters.”
Descriptive text is not available for this imageThrombolytic drugs should not be given to patients with active bleeding, a history of surgery or major trauma within the preceding two weeks, a brain tumor, or other known risks for intracerebral hemorrhage.

thrombopoietin mimetic agent

A drug that stimulates the bone marrow to produce more platelets than usual. Drugs from this class, e.g., romiplostim, are used to treat diseases such as immune thrombocytopenia.

topical hemostatic agent

Any substance that can be applied to a wound or an incision to keep it from bleeding. Examples include adhesives derived from collagen or glutaraldehyde, cellulose-based products, fibrin sealants, hydrogels, and thrombin.

uricosuric agent

A drug, e.g., probenecid or sulfinpyrazone, that increases the urinary excretion of uric acid by blocking renal tubular absorption, thereby reducing the concentration of uric acid in the blood. It is used to treat gout.

Probenecid and sulfinpyrazones are used to treat gout. Side effects of both include headache, gastrointestinal upset, epigastric pain, kidney stone formation, and peptic ulcer. These drugs should be avoided by patients with diminished renal function. Any uricosuric agent should be taken with milk, food, or antacids to reduce gastric distress. Patients should drink large volumes of water. Sodium bicarbonate (or potassium citrate) is prescribed simultaneously with these agents to alkalinize urine and keep uric acid crystals in solution.

vascular disrupting agent

Any of a class of medications used to destroy the blood supply of malignant tumors.

wetting agent

1. Any agent, such as a surfactant, that allows a fluid to spread over and coat a surface to which it is applied.
2. In radiographic wet film processing, a solution used after washing to reduce surface tension and accelerate water flow from the film to speed drying.