Psychology Chapter Drug Dependence and Interactions

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.

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.