Dose response curve

 

One of the helpful indicators of the dose needed which may be available is what is called the dose response curve which is a simple X-Y graph relating the magnitude of a stressor to the response of the recipient.

• Magnitude of stressor - The X axis usually plots the dose which is measured in milligrams,  micrograms  or grams per kilogram of body-weight.  This is important.  We are used, when taking pharmaceutical drugs, to the idea that dose is not judged on weight, whereas weight is in actuality extremely key to effect.  Thus dose in all these graphs is always taken into account and if you look on a site like EROWID every observation from those who contribute experiences describes their weight as well as the dose taken.  Commonly, it is the logarithm of the dose that is plotted on the X axis, and in such cases the curve is typically sigmoidal,  with the steepest portion in the middle

• Response of recipient  - The response is plotted on the Y axis.  The response may be a physiological or biochemical response, or even death (mortality).  The Y-axis is usually designated by percentages, which refer to the percentage of users registering a standard response (which may be death). The curve resulting is referred to as a quantal dose response curve, distinguishing it from a graded dose response curve, where response is continuous.

The first point along the graph where a response above zero is reached is usually referred to as a threshold-dose.  For most  ‘recreational’ drugs, the desired effects are found at doses slightly greater than the threshold dose. At higher doses, undesired side effects appear and grow stronger as the dose increases. The stronger a particular substance is, the steeper this curve will be.