Which DPP-4 inhibitor requires dosage modification when used with ketoconazole?

INI-CET EXAM -2025

Pharmacology

Easy

Appeared in: INI-CET EXAM -2025

Explanation

Saxagliptin is the correct answer as it undergoes significant metabolism by the cytochrome P450 3A4 (CYP3A4) enzyme.
Ketoconazole is a strong inhibitor of the CYP3A4 enzyme.
When taken together, ketoconazole blocks the breakdown of saxagliptin, causing its blood levels to rise to potentially toxic levels.
To prevent adverse effects, the dosage of saxagliptin must be reduced (typically to 2.5 mg daily) when co-administered with strong CYP3A4 inhibitors.

Option B: Linagliptin is primarily excreted unchanged in the bile and feces. It does not rely on CYP3A4 for its elimination, so its levels are not significantly affected by ketoconazole.
Option C: Sitagliptin is mainly eliminated unchanged by the kidneys through active tubular secretion. Its metabolism via CYP enzymes is very limited and not a major route of clearance.
Option D: Vildagliptin is primarily cleared through hydrolysis by enzymes in the cytoplasm, not by the cytochrome P450 system. Therefore, it is not susceptible to interactions with CYP3A4 inhibitors like ketoconazole.

Visual 1: Flowchart: A visual flowchart illustrating the metabolic pathways of the four listed DPP-4 inhibitors (Saxagliptin, Linagliptin, Sitagliptin, Vildagliptin), highlighting the central role of CYP3A4 for Saxagliptin and showing the alternative excretion/metabolism routes for the others.
Visual 2: Infographic: An infographic titled 'CYP3A4 Drug Interactions with Gliptins,' showing a lock-and-key analogy where ketoconazole 'blocks' the CYP3A4 enzyme, preventing it from 'processing' saxagliptin.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Drug-drug interactions involving DPP-4 inhibitors and cytochrome P450 (CYP) enzyme inhibitors as background academic context rather than a clinical decision trigger.
A nurse must always perform a thorough medication reconciliation to identify potential drug-drug interactions, especially when a new medication is prescribed.
Understanding the metabolic pathways of drugs is crucial for anticipating interactions. Knowing that ketoconazole is a potent enzyme inhibitor should prompt the nurse to review the patient's other medications for potential interactions.
Patient education is key. The nurse should educate the patient on the importance of not starting any new medications, including over-the-counter drugs or herbal supplements, without consulting their healthcare provider, as these can also cause significant drug interactions.

How to Approach the Question

First, identify the drug classes involved: DPP-4 inhibitors (for diabetes) and a strong CYP450 enzyme inhibitor (ketoconazole, an antifungal).
The question asks about a 'dosage modification,' which points to a significant drug-drug interaction.
Recall or deduce the mechanism of interaction: Ketoconazole inhibits the CYP3A4 enzyme. The question is essentially asking which of the listed DPP-4 inhibitors is metabolized by CYP3A4.
Systematically review the metabolic profile of each option:
Saxagliptin: Known to be a substrate for CYP3A4.
Linagliptin: Primarily excreted via bile/feces.

Concept Tested & Keywords

Concept Tested: Drug-drug interactions involving DPP-4 inhibitors and cytochrome P450 (CYP) enzyme inhibitors.
Stem keywords: DPP-4 inhibitor, dosage modification, ketoconazole
Lead-in keywords: Which

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