Changes

===Self-antagonism===

===Self-antagonism===

If some drugs are repeadtedly given its effect can decrease. This is called '''tachyphylaxis''' or '''desensitisation'''. If a gradual decrease in response to a drug occurs this is called '''tolerance''' and if the drug looses total therapeutic efficacy it is deemed '''refractory'''. Many types of mechanisms occur to cause this phenomenon, the most important include:

If some drugs are repeadtedly given its effect can decrease. This is called '''tachyphylaxis''' or '''desensitisation'''. If a gradual decrease in response to a drug occurs this is called '''tolerance''' and if the drug loses total therapeutic efficacy it is deemed '''refractory'''. Many types of mechanisms occur to cause this phenomenon, the most important include:

* chnage in receptor type

* chnage in receptor type

* physiological adaptation

* physiological adaptation

* active extrusion of the drug from cells

* active extrusion of the drug from cells

===Chemical Antagonism===

===Chemical Antagonism===