Pharmacology Ch. 4 Pharmacy Tech. Ch

 A receptor (the “Key”) interacts with a drug because it fits the structure of the receptor.  Once the drug reaches the receptor it is allowed into the cell where it cares out its function  Example: antihistamines  Some drugs interact with more than one receptor  Example: diphenhydramine- works with histamine receptors and with acetylcholine. *blocks histamine and causes drowsiness

 The place where a drug causes an effect to occur  Goal is to get the right drug, right amount, the right site of action and the right time for a desired effect.  Classic example: aspirin. - Aspirin’s site of action is the hypothalamus( a structure in the brain that regulates body temperature).

 How a drug works and produces its effects

 The lock into which the drug molecule fits as the key  The cellular material located at the site of action that interacts with the drug  Once the drug develops a bond, there are specific molecular changes that can occur

 Agonist- a drug that produces a predicted action, when bided to the correct receptor.  2 main properties: affinity-binding to the cell receptor structure efficacious- how well the drug does what it is designed to do  Antagonist- bind to a specific site on the cell to prevent the action of another substance. This, in-turn, produces the desired effect.  Target cell-large number of similar cells, such as a nerve cell

*The response of a drug is directly related to the amount of the drug taken or given.

 The point that represents the maximal response is called the ceiling.  Beyond the ceiling, the drug becomes toxic.  Once maximal response is achieved adding more drug will not be of benefit.

 Potency- the measurement of the strength of the drug that us required to have a specific effect on the body  -ED50- measurement of the amount of specific drug that will achieve ½ of the maximal response.  Drugs are tested on for their maximum effect(dangerous!), but just that they work.