{"id":25,"date":"2019-09-18T15:58:36","date_gmt":"2019-09-18T19:58:36","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/nursingpharmacology\/chapter\/1-2-pharmacokinetics\/"},"modified":"2022-01-09T16:23:27","modified_gmt":"2022-01-09T21:23:27","slug":"1-2-pharmacokineticsandpharmacodynamics","status":"publish","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/nursingpharmacology\/chapter\/1-2-pharmacokineticsandpharmacodynamics\/","title":{"raw":"1.2 Pharmacokinetics and Pharmacodynamics","rendered":"1.2 Pharmacokinetics and Pharmacodynamics"},"content":{"raw":"

Pharmacokinetics<\/h4>\r\n[pb_glossary id=\"512\"]Pharmacokinetics [\/pb_glossary]<\/strong> is the term that describes the four stages of absorption, distribution, metabolism, and excretion of drugs. [pb_glossary id=\"908\"]Drugs[\/pb_glossary]<\/strong> are medications or other substances that have a physiological effect when introduced to the body. There are four basic stages for a medication to go through within the human body: absorption, distribution, metabolism, and excretion. This entire process is sometimes abbreviated ADME. <\/strong>[pb_glossary id=\"519\"]Absorption[\/pb_glossary] <\/strong>occurs after medications enter the body and travel from the site of administration into the body's circulation. [pb_glossary id=\"520\"]Distribution[\/pb_glossary]<\/strong> is the process by which medication is distributed throughout the body. [pb_glossary id=\"517\"]Metabolism[\/pb_glossary]<\/strong> is the breakdown of a drug molecule. [pb_glossary id=\"522\"]Excretion[\/pb_glossary]<\/strong> is the process by which the body eliminates waste. Each of these stages is described separately later in this chapter.\r\n\r\nResearch scientists who specialize in pharmacokinetics must also pay attention to another dimension of drug action within the body: time. Unfortunately, scientists do not have the ability to actually see where a drug is going or how long it is active. To compensate, they use mathematical models and precise measurements of blood and urine to determine where a drug goes and how much of the drug (or breakdown product) remains after the body processes it. Other indicators, such as blood levels of liver enzymes, can help predict how much of a drug is going to be absorbed.\r\n\r\nPrinciples of chemistry are also applied while studying pharmacokinetics because the interactions between drug and body molecules are really just a series of chemical reactions. Understanding the chemical encounters between drugs and biological environments, such as the bloodstream and the oily surfaces of cells, is necessary to predict how much of a drug will be metabolized by the body.\r\n

Pharmacodynamics<\/h4>\r\n[pb_glossary id=\"523\"]Pharmacodynamics[\/pb_glossary]<\/strong> refers to the effects of drugs in the body and the mechanism of their action. As a drug travels through the bloodstream, it will exhibit a unique [pb_glossary id=\"505\"]affinity[\/pb_glossary]<\/strong> for the drug-receptor site, meaning how strongly it will bind to the site. Other components of pharmacodynamics include ion channels, enzymes, and the immune system.\r\n\r\nExamination of the ways in which drugs and receptor sites create a lock and key system (see Figure 1.2a[footnote]\"Drug and Receptor Binding<\/a>\" by Dominic Slausen at Chippewa Valley Technical College<\/a> is licensed under CC BY 4.0<\/a>[\/footnote]) is helpful to understand how drugs work and the amount of drug that may be left circulating within the bloodstream. This concept is broadly termed as drug [pb_glossary id=\"513\"]bioavailability[\/pb_glossary]<\/strong>. The bioavailability of drugs is an important feature that chemists and pharmaceutical scientists keep in mind when designing and packaging medicines.\r\n\r\n[caption id=\"attachment_24\" align=\"aligncenter\" width=\"521\"]\"Animated Figure 1.2a Pharmacodynamics: Drug and Receptor Binding[\/caption]\r\n

The Relationship Between Pharmacokinetics and Pharmacodynamics<\/h4>\r\nEssentially, pharmacokinetics is the movement of drugs through the body, and pharmacodynamics is the body's biological response to the drugs. Pharmacokinetics and pharmacodynamics need to be considered when administering medications. Figure 1.2b displays the relationship between pharmacokinetics and pharmacodynamics.\r\n\r\n[caption id=\"attachment_920\" align=\"alignnone\" width=\"1024\"]\"\" Figure 1.2b The Relationship Between Pharmacokinetics and Pharmacodynamics[\/caption]\r\n

Pharmacogenetics<\/h4>\r\nNo matter how effectively a drug works in a laboratory simulation, the performance in the human body will not always produce exactly the same results, and individualized responses to drugs have to be considered. Although many responses to medications may be anticipated, one's unique genetic makeup may also have a significant impact on one's response to a drug. [pb_glossary id=\"518\"] Pharmacogenetics [\/pb_glossary]<\/strong> is defined as the study of how people's genes affect their response to medicines.[footnote]This work is a derivative of Medicines by Design<\/a> by US Department of Health and Human Services, National Institute of Health, National Institute of General Medical Sciences and is available in the public domain.[\/footnote].\u00a0<\/sup>","rendered":"

Pharmacokinetics<\/h4>\n

Pharmacokinetics <\/a><\/strong> is the term that describes the four stages of absorption, distribution, metabolism, and excretion of drugs. Drugs<\/a><\/strong> are medications or other substances that have a physiological effect when introduced to the body. There are four basic stages for a medication to go through within the human body: absorption, distribution, metabolism, and excretion. This entire process is sometimes abbreviated ADME. <\/strong>Absorption<\/a> <\/strong>occurs after medications enter the body and travel from the site of administration into the body’s circulation. Distribution<\/a><\/strong> is the process by which medication is distributed throughout the body. Metabolism<\/a><\/strong> is the breakdown of a drug molecule. Excretion<\/a><\/strong> is the process by which the body eliminates waste. Each of these stages is described separately later in this chapter.<\/p>\n

Research scientists who specialize in pharmacokinetics must also pay attention to another dimension of drug action within the body: time. Unfortunately, scientists do not have the ability to actually see where a drug is going or how long it is active. To compensate, they use mathematical models and precise measurements of blood and urine to determine where a drug goes and how much of the drug (or breakdown product) remains after the body processes it. Other indicators, such as blood levels of liver enzymes, can help predict how much of a drug is going to be absorbed.<\/p>\n

Principles of chemistry are also applied while studying pharmacokinetics because the interactions between drug and body molecules are really just a series of chemical reactions. Understanding the chemical encounters between drugs and biological environments, such as the bloodstream and the oily surfaces of cells, is necessary to predict how much of a drug will be metabolized by the body.<\/p>\n

Pharmacodynamics<\/h4>\n

Pharmacodynamics<\/a><\/strong> refers to the effects of drugs in the body and the mechanism of their action. As a drug travels through the bloodstream, it will exhibit a unique affinity<\/a><\/strong> for the drug-receptor site, meaning how strongly it will bind to the site. Other components of pharmacodynamics include ion channels, enzymes, and the immune system.<\/p>\n

Examination of the ways in which drugs and receptor sites create a lock and key system (see Figure 1.2a[1]<\/sup><\/a>) is helpful to understand how drugs work and the amount of drug that may be left circulating within the bloodstream. This concept is broadly termed as drug bioavailability<\/a><\/strong>. The bioavailability of drugs is an important feature that chemists and pharmaceutical scientists keep in mind when designing and packaging medicines.<\/p>\n

\"Animated
Figure 1.2a Pharmacodynamics: Drug and Receptor Binding<\/figcaption><\/figure>\n

The Relationship Between Pharmacokinetics and Pharmacodynamics<\/h4>\n

Essentially, pharmacokinetics is the movement of drugs through the body, and pharmacodynamics is the body’s biological response to the drugs. Pharmacokinetics and pharmacodynamics need to be considered when administering medications. Figure 1.2b displays the relationship between pharmacokinetics and pharmacodynamics.<\/p>\n

\"\"
Figure 1.2b The Relationship Between Pharmacokinetics and Pharmacodynamics<\/figcaption><\/figure>\n

Pharmacogenetics<\/h4>\n

No matter how effectively a drug works in a laboratory simulation, the performance in the human body will not always produce exactly the same results, and individualized responses to drugs have to be considered. Although many responses to medications may be anticipated, one’s unique genetic makeup may also have a significant impact on one’s response to a drug. Pharmacogenetics <\/a><\/strong> is defined as the study of how people’s genes affect their response to medicines.[2]<\/sup><\/a>.\u00a0<\/sup><\/p>\n

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