- 1. A single, relatively large quantity of a substance, usually one intended for therapeutic use, such as a b. dose of a drug injected intravenously. 2. A masticated morsel of food or another substance ready to be swallowed, such as a b. of barium for x-ray studies. 3. In high-energy radiation therapy, a quantity of tissue-equivalent material placed in the radiation beam, over the surface of the irradiated region, to increase the absorbed dose in the superficial tissues. [L. fr. G. bolos, lump, clod]- intravenous b. a relatively large volume of fluid or dose of a drug or test substance given intravenously and rapidly to hasten or magnify a response; in radiology, rapid injection of a large dose of contrast medium to increase opacification of blood vessel s.
* * *1) a rounded mass: asa) a large pillb) a soft mass of chewed food2 a) a dose of a substance (as a drug) given intravenouslyb) a large dose of a substance given by injection for the purpose of rapidly achieving the needed therapeutic concentration in the bloodstream <the patient receives a \bolus dose to reach the minimum effective analgesic concentration (J. F. Camp)> <subcutaneous injection of a premeal \bolus of fast-acting insulin>
* * *n.a soft mass of chewed food or a pharmaceutical preparation that is ready to be swallowed.
* * *bo·lus (boґləs) [L., from Gr. bōlos lump] 1. a rounded mass of food or a pharmaceutical preparation ready to swallow. 2. a concentrated mass of pharmaceutical preparation given intravenously for diagnostic purposes, e.g., an opaque contrast medium or radioactive isotope. 3. a mass of scattering material, such as wax, paraffin, bags of water, or a rice-flour mixture, placed between the radiation source and the skin so as to achieve precalculated isodose pattern in the tissue irradiated.
Medical dictionary. 2011.