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Questions and Answers
What is defined as the lethal dose in 50% of animals?
What is defined as the lethal dose in 50% of animals?
What does the term 'synergism' refer to in pharmacology?
What does the term 'synergism' refer to in pharmacology?
Which type of dependence is illustrated by tobacco smoking?
Which type of dependence is illustrated by tobacco smoking?
What indicates a safer drug in terms of therapeutic index?
What indicates a safer drug in terms of therapeutic index?
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What term describes the combined action of two drugs equalling twice the effect of one?
What term describes the combined action of two drugs equalling twice the effect of one?
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What characterizes a chemical antagonist?
What characterizes a chemical antagonist?
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What type of non-competitive block involves an antagonist binding to a site distinct from the agonist's binding site?
What type of non-competitive block involves an antagonist binding to a site distinct from the agonist's binding site?
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How does protamine function as a chemical antagonist?
How does protamine function as a chemical antagonist?
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Which statement correctly describes reversible antagonists?
Which statement correctly describes reversible antagonists?
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Which receptors are primarily involved in the actions of smooth muscle antagonists?
Which receptors are primarily involved in the actions of smooth muscle antagonists?
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Study Notes
Dependence
- Psychological dependence is characterized by an intense craving for a drug even when it is not needed for its effects, for example tobacco smoking.
- Physical dependence is when the body becomes accustomed to a drug and requires it to function normally. For example, morphine, ethyl alcohol, or barbiturates.
Drug Interactions
- Additivity: The effect of two drugs combined equals the sum of their individual effects when administered separately. This is a 1 + 1 = 2 scenario.
- Synergism: The effect of two drugs combined is greater than the sum of the individual effects, resulting in a 1 + 1 > 2 scenario.
- Antagonism: The effect of one drug cancels out or reduces the effect of another drug. This is a 1 + 1 < 2 scenario.
Drug Antagonism
- Chemical antagonism: A type of antagonism that involves the direct chemical interaction of two drugs, preventing their action, as in the neutralization of heparin by protamine.
- Competitive antagonism: An antagonist binds reversibly to the same receptor site as the agonist, blocking the agonist's action. The effect of the antagonist can be overcome by increasing the concentration of the agonist.
- Non-competitive antagonism: An antagonist binds to a site on the receptor different from the agonist binding site, leading to an allosteric interaction. This interaction cannot be overcome by increasing the concentration of the agonist. The antagonist is not displaced by the agonist.
- Physiological antagonism: Two drugs acting at different receptors produce opposite effects, effectively canceling each other out.
Dosage and Response
- The therapeutic index (TI) is a measure of a drug's safety. A higher TI indicates a safer drug.
- The magnitude of a drug's effect depends on its concentration at the receptor site.
- As the concentration of a drug increases, the magnitude of its pharmacologic effect also increases. This relationship is known as a dose-response relationship.
- Potency: Refers to the amount of drug needed to produce a specific effect. A more potent drug produces the same effect at a lower dose.
- Efficacy: Refers to the maximum effect a drug can produce, regardless of the dose. A drug with higher efficacy produces a greater maximal effect.
Tolerance
- A decreased response to a drug after repeated administration. This may require higher doses to achieve the same effect.
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Description
Explore the concepts of psychological and physical dependence on drugs, including examples such as tobacco and morphine. Understand the different types of drug interactions, including additivity, synergism, and antagonism, alongside specific examples that illustrate these phenomena.
