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	~~Greetings~~. ~~Let me start by telling you~~ the ~~author'~~s ~~name~~ - ~~Kourtney Westerfield~~ and ~~she loves this~~ particular. ~~Data processing~~ is ~~where her primary income derives from~~ and ~~her salary has been really fulfilling~~. ~~To draw 3d graphics could~~ be the ~~hobby I~~'~~m going~~ to ~~never stop doing~~. ~~My family lives in New [https~~:~~//www~~.~~google~~.~~com/search?hl~~=~~en&gl~~=~~us&tbm~~=~~nws&q~~=~~Hampshire&btnI~~=~~lucky Hampshire]~~. ~~Check out~~ the ~~latest news on his website~~: ~~http~~://~~rv4x4~~.~~com~~/?q=~~miley-cyrus-just-cant-be-tamed~~<br><br>~~Feel free to visit my blog post~~ - [http://~~rv4x4~~.com/~~?q=miley~~-~~cyrus~~-~~just~~-~~cant~~-be-~~tamed disney casting~~]		{{mergeto\|Pharmacodynamics\|discuss=Talk:Pharmacodynamics#Merger proposal\|date=November 2013}}
			{{Unreferenced\|date=August 2009}}
			The '''action of drugs''' on the human body is called [[pharmacodynamics]], and what the '''body does with the drug''' is called [[pharmacokinetics]]. The drugs that enter the human tend to stimulate certain receptors, ion channels, act on enzymes or transporter proteins. As a result, they cause the human body to react in a specific way.

			There are two different types of drugs:

			*[[Agonist]]s - they stimulate and activate the receptors
			*[[Receptor antagonist\|Antagonist]]s - they stop the agonists from stimulating the receptors

			Once the receptors are activated, they either trigger a particular response directly on the body, or they trigger the release of hormones and/or other endogenous drugs in the body to stimulate a particular response.

			== Short Note on Receptors ==

			Drugs interact with receptors by bonding at specific binding sites. Most receptors are made up of proteins, and the drugs can therefore interact with the amino acids to change the conformation of the receptor proteins.

			These interactions are very basic, just like that of other chemical bondings:

			===Ionic Bonds===

			Mainly occur through attractions between opposite charges; for example, between protonated amino (on [[salbutamol]]) or quaternary ammonium (e.g. [[acetylcholine]]), and the dissociated carboxylic acid group. Similarly, the dissociated carboxylic acid group on the drug can bind with amino groups on the receptor.

			This type of bond is very strong, and varies with the inverse of the distance between the atoms so that it can act over large distances.

			Cation-π interactions can also be classified as ionic bonding. This type of interaction occurs when a cation, e.g. acetylcholine, interacts with the negative π bonds on an aromatic group of the receptor.

			'''Ion-dipole''' and '''dipole-dipole''' bonds have similar interactions, but are more complicated and are weaker than ionic bonds.

			=== Hydrogen bonds ===
			There is a small but significant attraction between hydrogen atoms and polar functional groups (e.g. the hydroxyl [-OH] group). These so-called hydrogen bonds only act over short distances, and are dependent on the correct alignment between functional groups.

			Receptors are located on all cells in the body. The same receptor can be located on different organs, and even on different types of tissues. There are also different subtypes of receptor which elicit different effects in response to the same agonist. For example, there are two types of histamine receptor: H1 and H2. Activation of the H1 subtype receptor causes contraction of smooth muscle, whereas activation of the H2 receptor stimulates gastric secretion.

			It is this phenomenon that gives rise to drug specificity. Of course, drugs do not only act on receptors: they also act on ion channels, enzymes, and cell transporter proteins.

			== How shape of drug molecules affect drug action ==

			When talking about the '''shape of molecules''', biochemists are mainly concerned with the three-dimensional conformation of drug molecules. There are many isomers of a particular drug, and each one will have its own effects. Differences in isomer affect not only what the drug activates, but also changes the potency of each drug.

			=== Potency ===

			'''Potency''' is a measure of how much a drug is required in order to produce a particular effect. Therefore, only a small dosage of a high potency drug is required to induce a large response. The other terms used to measure the ability of a drug to trigger a response are:
			*Intrinsic Activity which defines:
			**Agonists as having Intrinsic Activity = 1
			**Antagonists as having Intrinsic Activity = 0
			**and, Partial Agonist as having Intrinsic Activity between 0 and 1

			*Intrinsic Efficacy also measures the different activated state of receptors, and the ability for a drug to cause maximum response without having to bind to all the receptors.

			=== The specificity of drugs ===

			Drug companies invest significant effort in designing drugs that interact specifically with particular receptors {{Citation needed\|date=July 2008}}, since non-specific drugs can cause more side effects.

			An example is the [[endogenous]] drug acetylcholine (ACh). ACh is used by the [[parasympathetic nervous system]] to activate muscarinic receptors and by the neuromuscular system to activate nicotinic receptors. However, the compounds muscarine and nicotine can each preferentially interact one of the two receptor types, allowing them to activate only one of the two systems where ACh itself would activate both.

			=== Affinity ===

			The specificity of drugs cannot be talked about without mentioning the '''affinity''' of the drugs. The affinity is a measure of how tightly a drug binds to the receptor. If the drug does not bind well, then the action of the drug will be shorter and the chance of binding will also be less. This can be measured numerically by using the dissociation constant K<sub>D</sub>. The value of K<sub>D</sub> is the same as the concentration of drug when 50% of receptors are occupied.

			The equation can be expressed as K<sub>D</sub> = <math> \frac{[drug][receptor]}{[complex]}</math>

			But the value of K<sub>D</sub> is also affected by the conformation, bonding and size of the drug and the receptor. The higher the K<sub>D</sub> the lower the affinity of the drug.

			==References==
			{{reflist}}

			==External links==
			*[http://www.merckmanuals.com/home/drugs/drug_dynamics/drug_action.html Drug Action] - [[Merck Manual]] Home Health Handbook
			*[http://chestofbooks.com/health/materia-medica-drugs/Introduction-to-Materia-Medica-and-Pharmacology/Chapter-I-Pharmacology-Physiologic-Action-Of-Drugs.html Pharmacology. Physiologic Action Of Drugs]
			*[http://www.elmhurst.edu/~chm/vchembook/650drugs.html Introduction to Drug Action]

			[[Category:Pharmacodynamics]]
			[[Category:Pharmacokinetics]]

en>GrouchoBot: r2.7.2) (Robot: Adding sl:Morinova ploskev

2012-03-27T16:28:25Z

r2.7.2) (Robot: Adding sl:Morinova ploskev

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Greetings. Let me start by telling you the author's name - Kourtney Westerfield and she loves this particular. Data processing is where her primary income derives from and her salary has been really fulfilling. To draw 3d graphics could be the hobby I'm going to never stop doing. My family lives in New [https://www.google.com/search?hl=en&gl=us&tbm=nws&q=Hampshire&btnI=lucky Hampshire]. Check out the latest news on his website: http://rv4x4.com/?q=miley-cyrus-just-cant-be-tamed<br><br>Feel free to visit my blog post - [http://rv4x4.com/?q=miley-cyrus-just-cant-be-tamed disney casting]

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en>GrouchoBot: r2.7.2) (Robot: Adding sl:Morinova ploskev