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1.Introduction to Pharmacology
Objectives
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Understand the cell signaling process initiated by drug molecule binding
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Understand the molecular mechanisms of drug-receptor interaction
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Understand how drug effects are produced by drug actions
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Understand the effects of drug binding to different receptor subtypes
Concepts to Learn
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Cell signaling process
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Drug-receptor binding process
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Drug-receptor interaction
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Electrical and chemical responses to drug-binding
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Selectivity of drug-binding
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Affinity of drug-binding
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Drug interaction with different receptor subtypes
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Drug agonism and antagonism
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Competitive and non-competitive binding
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1.1.Pharmacological Agents
Objectives
Concepts to Learn
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Working definition of drug
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What is medicine and drug, and how it works
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Cell signaling process
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Therapeutic medicine and preventive medicine
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Endogenous vs. exogenous biochemicals
A drug is simply a molecule that serves a signal to the cell so that bodily functions can be altered by this external signal. Normally, a cell automatically self-regulates itself to produces its function and maintains its homeostatic state.
Disease is often caused by perturbation of this homeostatic state such that the cell is unable to restore its normal function. In order to restore its function, some external help is needed. This external help often comes from a drug molecule introduced to the cell. This serves as a signal to the cell that triggers a cascade of events that restores the normal cellular function hopefully. This is how drug therapy works.
A cell also receives internal signals that alter its function. These internal signals are also carried by molecules that circulate inside the body. Examples of these molecules are hormones, neurotransmitters and neuromodulators. The cell responds to these internal signals similar to the drug signals. In fact, that is how the body regulates its functions – by releasing these hormones and neurotransmitters from one cell for another cell to respond to.
Because cells rely on these internal signals to turn on/off its function, this process is called the signaling process. It is used to regulates its function, such as turning on growth and development (or even turning on programmed cell death), maintaining homeostasis, repairing damages, or whatever that is needed for its normal function. When a cell is unable to restore its function, it leads to dysfunction. Sometimes, all it takes is a boost from an external signal to turn on its cellular process when the internal signal is insufficient to do so. This is what drug does and how drugs work.
Drug molecules merely substitute these endogenous (synthesized within the body) internal molecules by exogenous (synthesized outside the body) drug molecules to alter the function of downstream cells. The resulting changes to these downstream cells will produce the physiological changes and/or psychological effects on the brain. Thus, although drugs can be used as a therapy to help dysfunctional cells to restore its function, they can also be used to stimulate new functions or serve as preventive medicine even when the cells are not necessarily sick.
Thus, the only difference between drug molecules and biogenic molecules is where they are synthesized. A hormone molecule, such as insulin, is not a drug when it is synthesized inside the body in the pancreas normally, but the same insulin molecule is a drug when it is synthesized outside the body and then injected into the body for diabetic therapy. Therefore, the definition of drug is rather artificial. The cell cannot distinguish the difference between an insulin molecule that is synthesized inside the body from another insulin molecule that is synthesized outside the body. That is because the same insulin molecules are identical and indistinguishable from each other chemically.
Summary
A drug is a molecule that alters cellular functions. It serves as a signal to produce a cascade of events that the cell responds to. As a result, the cell will either restore its normal function (return to its homeostatic state) or produce new function (change to a new state). These chemical signals can come from internal to the body or introduce into the body externally. When they are introduced into the body, it is called a drug. When the same molecule is synthesized by the body, it is not considered as a drug. Thus, a drug molecule is a “chemical knob” that turn on/off cellular functions, which will result in changing physiological and psychological responses as a result of the cellular changes.
Q&A
What is a drug?
A drug is a molecule that, when taken into the body, will alter bodily functions.
A drug is any substance that produces an effect to the body when administered into the body or an organism. It is essentially a chemical signal to the cell to initiate some cellular functions. The reason why medicine can help the body to perform its function is when there is a point that the body or the cell cannot repair or correct its defects, then an external signal may help the cell to restart its function.
What does a drug molecule do to a cell?...
