CYP-450 inducers are:
**Core Concept**
Cytochrome P450 (CYP-450) enzymes are a family of liver enzymes responsible for the metabolism of various drugs. Inducers of CYP-450 enzymes increase their expression and activity, leading to enhanced metabolism of co-administered drugs. This can result in decreased plasma concentrations and reduced efficacy of these drugs.
**Why the Correct Answer is Right**
DDT (Dichlorodiphenyltrichloroethane) is a known inducer of CYP-450 enzymes. It increases the expression and activity of these enzymes, leading to increased metabolism of co-administered drugs. This is a classic example of enzyme induction, where a substance increases the activity of an enzyme, rather than inhibiting it. DDT's mechanism of inducing CYP-450 enzymes is thought to involve the activation of the pregnane X receptor (PXR), a nuclear receptor that regulates the expression of CYP-450 genes.
**Why Each Wrong Option is Incorrect**
**Option A:** Cimetidine is actually an inhibitor of CYP-450 enzymes, particularly CYP3A4 and CYP1A2. It reduces the activity of these enzymes, leading to increased plasma concentrations and potential toxicity of co-administered drugs.
**Option B:** Ketoconazole is a potent inhibitor of CYP-450 enzymes, particularly CYP3A4. It reduces the activity of these enzymes, leading to increased plasma concentrations and potential toxicity of co-administered drugs.
**Option C:** Erythromycin is also an inhibitor of CYP-450 enzymes, particularly CYP3A4. It reduces the activity of these enzymes, leading to increased plasma concentrations and potential toxicity of co-administered drugs.
**Clinical Pearl / High-Yield Fact**
When prescribing medications, it is essential to consider potential interactions with other drugs that may be metabolized by CYP-450 enzymes. DDT's induction of these enzymes highlights the importance of monitoring plasma concentrations and adjusting dosages accordingly. Additionally, patients taking medications that are substrates of CYP-450 enzymes should be warned about potential interactions with DDT or other inducers.
**✓ Correct Answer: D. DDT**