<p><strong>Drugs that Inhibit or Induce Cytochrome P450 3A4 Enzymes</strong>: In vitro studies suggested that the oxidative metabolism of Pazopanib in human liver microsomes is mediated primarily by CYP3A4, with minor contributions from CYP1A2 and CYP2C8. Therefore, inhibitors and inducers of CYP3A4 may alter the metabolism of Pazopanib.<br />
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<strong>CYP3A4 Inhibitors</strong>: Coadministration of Pazopanib with strong inhibitors of CYP3A4 (e.g., Ketoconazole, Ritonavir, Clarithromycin) increases Pazopanib concentrations and should be avoided. Consider an alternate concomitant medication with no or minimal potential to inhibit CYP3A4. If coadministration of a strong CYP3A4 inhibitor is warranted, reduce the dose of Pazopanib to 400 mg. Grapefruit or grapefruit juice should be avoided as it inhibits CYP3A4 activity and may also increase plasma concentrations of Pazopanib.<br />
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<strong>CYP3A4 Inducers</strong>: CYP3A4 inducers, such as Rifampin, may decrease plasma Pazopanib concentrations. Consider an alternate concomitant medication with no or minimal enzyme induction potential. Pazopanib should not be used if chronic use of strong CYP3A4 inducers cannot be avoided.<br />
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<strong>Drugs that Inhibit Transporters</strong>: In vitro studies suggested that Pazopanib is a substrate of P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP). Therefore, absorption and subsequent elimination of Pazopanib may be influenced by products that affect P-gp and BCRP. Concomitant treatment with strong inhibitors of P-gp or BCRP should be avoided due to risk of increased exposure to Pazopanib. Selection of alternative concomitant medicinal products with no or minimal potential to inhibit P-gp or BCRP should be considered.<br />
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<strong>Effects of Pazopanib on CYP Substrates</strong>: Results from drug-drug interaction trials conducted in cancer patients suggest that Pazopanib is a weak inhibitor of CYP3A4, CYP2C8, and CYP2D6 in vivo, but had no effect on CYP1A2, CYP2C9, or CYP2C19. Concomitant use of Pazopanib with agents with narrow therapeutic windows that are metabolized by CYP3A4, CYP2D6, or CYP2C8 is not recommended. Coadministration may result in inhibition of the metabolism of these products and create the potential for serious adverse events.<br />
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<strong>Effect of Concomitant Use of Pazopanib and Simvastatin</strong>: Concomitant use of Pazopanib and Simvastatin increases the incidence of ALT elevations. Across monotherapy trials with Pazopanib, ALT greater than 3 x ULN was reported in 126/895 (14%) of patients who did not use statins, compared with 11/41 (27%) of patients who had concomitant use of Simvastatin. If a patient receiving concomitant Simvastatin develops ALT elevations, follow dosing guidelines for Pazopanib or consider alternatives to Pazopanib. Alternatively, consider discontinuing Simvastatin. Insufficient data are available to assess the risk of concomitant administration of alternative statins and Pazopanib.</p>