Lecture 4: Pharmacology: How Drug's Work

Pharmacology: The scientific study of the actions of drugs and their effects on a living organism


Pharamacokinetics: The branch of pharmacology concerned with the actions of a body on an administered drug. 


Absorption: The process and mechanisms by which drugs pass from the outside world into the bloodstream. 


Fat-soluble: Also called lipid-soluble, this refers to substances that dissolved in fats or oils. 


Water-soluble: Substances that dissolve in water. 


Bioavailability: The degree to which the original drug dose reaches its site of action. 


Route of administration: The method by which a drug is taken into the body. 


Oral Administration: liquids, pills, tablets, capsules. Dissolves in the gastric fluids. Active ingredients must be resistant to destruction by stomach acids and enzymes. Generally takes 20-30 minutes to reach the brain. 


First-pass effect: The phenomenon by which orally administered drugs are metabolized by liver enzymes before they reach the general circulation, thus significantly reducing their bioavailability. 


Transdermal administration: the administration of drugs to the skin as creams or patches. 


Sublingual administration: The administration of drugs under the tongue. 


Buccal administration: The administration of drugs across the mucous membrance of the cheek. 


Intravenous injection: The administration of drugs by injecting them into a vein. 


Intramuscular injection: The administration of drugs by injecting them into a muscle. 


Subcutaneous injections: The administration of drugs by injecting them directly underneath the skin. 


Distribution: The transport of drugs to their site (s) of action in the body


Drug depot: An area of the body in which a drug can be accumulated or stored, but where no biological effect of the drug occurs. 


Plasma proteins: Proteins found in the blood that serve many functions, including transport of some substances. 

Area postrema: The vomiting center of the brain, BBB is absent around this chemical trigger zone. 


Biotransformation: The biochemical modifications made by an organism on a chemical compound in order to make it easier to be excreted by the body. 


Metabolites: chemical products of metabolism. 


Cytochrome P450 (CYP450): A superfamily of enzymes that play a role in many activities, including metabolism of drugs and toxins. 


First-order kinetics: The rate of the drugs metabolism is proportional to the concentration of the drug. 


Zero-order kinetics: The rate of the drug’s metabolism is constant over time and independent of the concentration of the drug. 


Half-life: The time it takes for the amount of drug in the body to be reduced by 50 percent. 


Elimination: The process of substances leaving the body, usually through urine, breath, digestion, and sweat


Pharmacodynamics: The branch of pharmacology concerned with the actions of an administered drug on an organism. 


Drug action: The molecular changes produced by a drug when it binds to a receptor, and the physiological or psychological changes that occur as a result. 


Ligand: Any man-made or natural substance, such as a drug or neurotransmitter, which binds to a receptor. 


Affinity: How well a drug binds to it’s target


Agonist: A  chemical or drug that mimics the effects of a neurotransmitter.


Partial Agonist: A chemical that binds to an activates a receptor, but not as completely as a ful agonist. 


Antagonist: A chemical or drug that inhibits the effects of a neurotransmitter. 


Set: The effect of a person’s expectations on drug effect. 


Placebo: A substance or procedure taht has no therapeutic effect and may be used as a control in experimental research designs or to reinforce a patient’s expectation of recovery. 

Placebo effect: When a placebo treatment produces a perceived or actual improvement in a medical condition. 


Setting: The physical, social, and cultural environment in which a drug is used. 


Side effects: Pharmacological actions that occur in addition to the main drug action. 


Dose-response curve: A measure of a drug’s effectiveness as a function of the dose administered


Potency: The minimum dose of a drug that yields its desired effect. 


Efficacy: The maximum effect that can be produced by a drug: the peak of the dose-response curve. 


Therapeutic Index: A measure of a drug’s safety given as the ratio of the average lethal dose of a drug divided by the therapeutic dose, LD50/ED50


Margin of safety: An index of a drug’s effectiveness and safety LD1/ED99


Additive effects: The combined effect of drugs is equal to the sum of each drug’s effect alone. 


Synergistic: The combined effect of drugs is greater than the sum of each drug’s effect alone. 


Antagonism: The combined effect of drugs is less than the sum of each drug’s effect alone. 


Tolerance: A phenomenon whereby chronic use of a drug can decrease the drug’s effects. 


Acute tolerance: Tolerance that occurs within a single exposure to a drug. 


Metabolic tolerance: Tolerance that occurs when the body speed’s up the metabolism of a drug by increasing the production of certain liver enzymes. 


Cellular tolerance: Tolerance that occurs when cells adapt to the presence of a drug by changing receptor density 


Homeostasis: The tendency of the body to try to maintain equilibrium, even when faced with external changes. 


Downregulation: The process by which a cell decreases the number of receptors in response to an increased amount of neurotransmitter in the synapse. 


Upregulation: The process by which a cell increases the number of receptors in response to an increased amount of neurotransmitter in the synapse. 

Behavioral tolerance: Tolerance that occurs when people learn to “handle themselves” while on a drug by developing resistance to the drugs effects. 


Crosstolerance: Resistance to the effects of a drug as a result of tolerance previously developed to a pharmacologically similar compound. 


Reverse tolerance: Also called sensitization or kindling, this is when repeated use of a drug causes increased sensitivity to its effects. 


Select tolerance: When the body develops tolerance to different aspects of the drug at different rates. 


of a chronically used drug. 






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