A patient on treatment with ketoconazole for a fungal disease develops Gastroesophageal Reflux Disease (GERD). Which of the following drugs should not be prescibed to him:
**Core Concept**
Ketoconazole is a potent inhibitor of the cytochrome P450 enzyme system, particularly CYP3A4, which is responsible for the metabolism of many drugs. The development of GERD in a patient on ketoconazole treatment may necessitate the avoidance of certain medications that can exacerbate this condition or interact with ketoconazole.
**Why the Correct Answer is Right**
The correct answer is Omeprazole, a proton pump inhibitor (PPI) commonly used to treat GERD. However, ketoconazole inhibits the metabolism of omeprazole, leading to increased levels of the latter. This can result in prolonged inhibition of gastric acid secretion, potentially causing increased risk of Clostridioides difficile infection, or interactions with other medications metabolized by the same enzyme system.
**Why Each Wrong Option is Incorrect**
**Option A:** Ranitidine, an H2 receptor antagonist, can be used to treat GERD but does not interact significantly with ketoconazole.
**Option B:** Metoclopramide, a prokinetic agent, can be used in conjunction with GERD treatment but does not interact significantly with ketoconazole.
**Option C:** Loperamide, an opioid receptor agonist used for diarrhea, does not interact significantly with ketoconazole.
**Clinical Pearl / High-Yield Fact**
When prescribing medications to patients on ketoconazole, it is essential to consider potential interactions and contraindications, as the enzyme inhibition caused by ketoconazole can have significant effects on the metabolism of other drugs.
**Correct Answer:** A. Omeprazole, a proton pump inhibitor commonly used to treat GERD, should not be prescribed to a patient on ketoconazole treatment due to the risk of increased levels and potential interactions.