Drug Tolerance

Definition

Drug tolerance refers to the phenomenon where an individual requires higher doses of a drug to achieve the same effect over time. This occurs as the body adapts to the presence of the drug, often through physiological changes that reduce the drug's effectiveness.

5 Must Know Facts For Your Next Test

1. Drug tolerance can develop for a wide range of substances, including prescription medications, recreational drugs, and even some over-the-counter medications.
2. The development of tolerance is often a precursor to physical dependence, where the body becomes reliant on the drug to function normally.
3. Tolerance can occur through various mechanisms, such as changes in receptor sensitivity, drug metabolism, or the body's compensatory responses to the drug's effects.
4. Rapid tolerance development is common with certain drugs, such as opioids and benzodiazepines, increasing the risk of overdose and other adverse effects.
5. Tolerance can be specific to a particular drug or class of drugs, or it can be more general, affecting the body's response to a wide range of substances.

Review Questions

• Explain how drug tolerance can lead to the development of physical dependence.
  • As an individual develops tolerance to a drug, they require higher doses to achieve the same desired effect. This can lead to physical dependence, where the body becomes reliant on the presence of the drug to maintain normal function. When the drug is discontinued or the dose is reduced, the individual may experience withdrawal symptoms as the body struggles to restore homeostasis in the absence of the drug. This cycle of tolerance and dependence is a key feature of substance use disorders and can contribute to the progression of addiction.
• Describe the various mechanisms by which drug tolerance can develop.
  • Drug tolerance can develop through several physiological mechanisms, including changes in receptor sensitivity, drug metabolism, and compensatory responses by the body. For example, with repeated exposure to a drug, the body may downregulate the number or sensitivity of receptors targeted by the drug, reducing its effectiveness. The body may also increase the activity of enzymes that metabolize the drug, leading to faster clearance and a reduced drug concentration. Additionally, the body may activate compensatory mechanisms, such as the release of counteracting hormones or the activation of alternative pathways, to maintain homeostasis in the presence of the drug. These adaptations contribute to the development of tolerance, making it necessary to increase the drug dose to achieve the desired effect.
• Analyze the relationship between rapid tolerance development and the risk of overdose for certain drugs.
  • Drugs that induce rapid tolerance development, such as opioids and benzodiazepines, pose a significant risk of overdose. As an individual develops tolerance, they may increase their drug dosage to compensate, unaware that their body's ability to tolerate the drug has changed. This can lead to a situation where the individual takes a dose that was previously safe, but is now potentially lethal due to the body's altered response. The rapid onset of tolerance can also mask the body's natural warning signs, making it more difficult for the individual to recognize when they are reaching dangerous levels of drug consumption. This heightened risk of overdose is a critical concern with rapidly developing drug tolerances and underscores the importance of careful monitoring and management of these substances.

Related terms

Dependence:

A state in which an individual requires a drug to function normally and experiences withdrawal symptoms when the drug is discontinued.

Addiction:

A chronic, relapsing disorder characterized by compulsive drug seeking and use, despite harmful consequences.

Homeostasis:

The process by which the body maintains a stable internal environment, which can be disrupted by the presence of drugs leading to the development of tolerance.