Tolerance and drug resistance can be a consequence of?

RRB Staff Nurse Mumbai-2015

Pharmacology

Medium

Appeared in: RRB Staff Nurse Mumbai-2015

Explanation

Tolerance is a state where a higher dose of a drug is needed to produce the same therapeutic effect.
Increased metabolic degradation, primarily through the induction of liver enzymes (e.g., the Cytochrome P-450 system), causes the drug to be cleared from the body more rapidly.
This faster clearance reduces the drug's concentration at its site of action, diminishing its effect and leading to pharmacokinetic tolerance.
Common enzyme-inducing drugs include rifampin, carbamazepine, and phenobarbital.

Option A: Drug dependence is a physiological or psychological need for a drug to prevent withdrawal symptoms. It is an adaptation to the drug's presence but does not cause the decreased response seen in tolerance.
Option C: Depressed or reduced renal excretion leads to slower elimination of a drug. This causes the drug to accumulate in the body, increasing its concentration and the risk of toxicity, which is the opposite of tolerance.
Option D: This describes the mechanism of a prodrug, which is a compound that is inactive until it is metabolized by the body into its active form. This activation process is required for the drug's therapeutic effect and is not a mechanism of tolerance.

Visual 1: Diagram: Liver Enzyme Induction. A visual showing a drug entering the liver, stimulating the production of more CYP450 enzymes, which then metabolize subsequent doses of the drug more rapidly.
Visual 2: Graph: Drug Concentration vs. Time. A chart comparing the plasma concentration curve of a drug after a single dose versus after chronic administration with enzyme induction, illustrating a lower peak concentration and shorter half-life in the latter case.

Clinical Relevance

Nursing practice connection: Knowing Drug Tolerance and Pharmacokinetics helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Nurses must recognize that a decrease in a drug's effectiveness over time may signal tolerance due to enzyme induction, particularly if the patient has started a new medication known to be an inducer (e.g., rifampin, carbamazepine).
It is a critical nursing responsibility to monitor for therapeutic failure and collaborate with the prescriber for potential dose adjustments or drug changes.
Patient education is vital. Advise patients to inform their healthcare provider of all medications they are taking, including over-the-counter drugs and herbal supplements like St. John's wort, as these can induce enzymes and compromise the efficacy of prescribed drugs.

How to Approach the Question

First, understand the key term in the question: 'Tolerance' means requiring a higher dose of a drug to achieve the same effect.
Next, analyze each option based on its effect on drug concentration in the body (pharmacokinetics).
Evaluate Option A: Is drug dependence a cause of tolerance or an associated outcome? It's an associated outcome.
Evaluate Option B: How does increased metabolism affect drug levels? It lowers them, meaning more drug would be needed for the same effect. This matches the definition of tolerance.
Evaluate Option C: How does depressed excretion affect drug levels? It raises them, which is the opposite of tolerance and can lead to toxicity.
Evaluate Option D: Is drug activation a mechanism of tolerance? No, it's a mechanism for how some drugs (prodrugs) start to work.

Concept Tested & Keywords

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