Skip to Main Content

We have a new app!

Take the Access library with you wherever you go—easy access to books, videos, images, podcasts, personalized features, and more.

Download the Access App here: iOS and Android

agenesia, agenesis

(ā″jĕ-nē′zh(ē-)ă, ā″ jen′ĕ-sis) [1an- + -genesis] 1. Failure of an organ or part to develop or grow. 2. Lack of potency.


(ā′jĕnt) [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.

alkylating a. 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 a. 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: alpha blocker. SEE: beta-adrenergic blocking a.

anabolic a. 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; ergonomic aid.

image Indiscriminate 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 a. Anxiolytic.

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

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

beta-adrenergic blocking a. 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: beta blocker.

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

buffering a. Buffer.

bypassing a. 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 a. Any chemical, biological, radiologic, nuclear, or explosive agent ...

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.