PHARMACOLOGY

 DOSE RESPONSE RELATIONSHIP ::

The exact relationship between the dose and the response depends on the biological object under observation the response measured and the drug employed The measurement of the relationship between the dose of a drug and its response is a valuable means of defining the potency of the drugs it indicates not only the nature of the effect at a given dose but the range within which the effect can be varied The relationship may be studied by taking the responses to different concentrations of drug The concentration is increased step by step and the next dose is given only after the effect of preceeding dose has returned to normal The curve obtained is known as graded dose response curve 

        Each drug produces a characteristic curve for a specified act of conditions However in general it is the characteristic that the administration of a suitably active drug will produce response that is proportionate to the dose provided that amount of drug added is above the threshold necessary to elicit the response The response may increase logarthmically over a certain range of dose At a particular dose there is diminishing effect reaching a steady level where further increase in dose dose not produce any further increase in the response This is known as maximum or ceiling effect The responses to different concentrations if plotted against log dose the characteristic dose response curve is S shaped