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Bias is the deviation of results from the truth, due to systematic error in the method used. There are many different types of bias.

bioassay (or biological assay)

Used to determine the potency of a physical, chemical or biological agent, by means of a biological indicator i.e. measuring the response of living organisms or tissues to a test treatment.


Bioavailability (or simply availability) is an indicator of the percent of a drug dose entering the systemic circulation after administration of a given dosage form. The amount of drug absorbed is taken as a measure of the ability of the formulation to deliver drug to the sites of drug action.


The percent of dose entering the systemic circulation after administration of a given dosage form. More explicitly, the ratio of the amount of drug “absorbed” from a test formulation to the amount “absorbed” after administration of a standard formulation. Frequently, the “standard formulation” used in assessing bioavailability is the aqueous solution of the drug, given intravenously.


The science and study of the ways in which the pharmaceutical formulation of administered agents can influence their pharmacodynamic and pharmacokinetic behavior. Differences in pharmaceutical properties can cause substantial differences in the biologic properties – and therapeutic usefulness – of preparations which are identical with respect to their content of active ingredient.


Factors that act to convert a drug to another form. Typically, in the process of drug elimination drugs are biotransformed to inactive, more polar, water-soluble products that can be more easily excreted in the urine. However, the products of biotransformation can also be active compounds in themselves, or may be toxic. The major organ of biotransformation is the liver.


The movement of drugs into, through, and out of biological organisms or their organs/tissues. The study of biotranslocation determines how chemicals cross cellular membranes and other biological barriers.

blind experiment

A form of experiment in which the participants are, to some degree, kept ignorant of the nature and doses of materials administered during the experiment, to prevent a prejudiced interpretation of the drug effects observed, and to prevent a presumed knowledge of effects to be expected from influencing the kinds of effects manifested by a subject. In a 'single-blind' experiment, one participant – usually the subject – is left uninformed. In a 'double-blind' experiment two participants – usually the subject and observer – are uninformed, and in 'triple-blind' experiment the subject, the observer, and the person responsible for the actual administration of the drug are left unaware of the nature of the material administered. In clinical experimentation the use of blind experimentation is frequently associated with the use of dummy or placebo medication as part of the experimental design, and the use of a 'cross-over' experimental design.


The maximum amount of drug or radioligand, usually expressed as picomoles (pM) per mg protein, which can bind specifically to the receptors in a membrane preparation. Bmax be used to measure the density of receptor sites in a particular test sample.


abnormally slow breathing rate; respiratory depression


Medical term for grinding the teeth and clenching the jaw.

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