Drug Interactions between benzgalantamine and cobicistat / elvitegravir / emtricitabine / tenofovir disoproxil

Using cobicistat together with tenofovir can increase the effects of tenofovir, which can cause new or worse kidney problems. You may need a dose adjustment or more frequent monitoring by your doctor to safely use both medications. Contact your doctor if your condition changes or you experience increased side effects. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

Cobicistat is a medication used to boost the effects of some medications that treat HIV infection. However, using cobicistat together with other HIV medications, such as emtricitabine, may alter the blood levels and effects of both medications. Using emtricitabine with cobicistat may reduce or increase blood levels of cobicistat. Reduced blood levels of cobicistat may make cobicistat less effective and may cause overall HIV treatment to be less effective. Cobicistat may increase blood levels of emtricitabine which may increase the risk of side effects. Talk to your doctor or pharmacist if you have any questions on how to use these medications properly. Your doctor may be able to prescribe alternatives that do not interact, or you may need a dose adjustment or more frequent monitoring to safely use both medications. Contact your doctor if your condition changes or you experience increased side effects. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

Consumer information for this interaction is not currently available.

MONITOR: Coadministration with potent inhibitors of CYP450 2D6 and/or 3A4 may increase the plasma concentrations of galantamine, which is also an active metabolite of benzgalantamine. Up to 75% of galantamine is eliminated via metabolism and in vitro studies have identified CYP450 2D6 and 3A4 as the major isoenzymes involved. The systemic exposure (AUC) of galantamine (4 mg, 8 mg, or 12 mg twice daily) increased by 40%, 45%, and 48%, respectively, when administered to healthy volunteers (n=16) also receiving the strong CYP450 2D6 inhibitor paroxetine. Similarly, the strong CYP450 3A4 inhibitor ketoconazole (200 mg twice daily) increased the AUC of galantamine (4 mg twice daily) by 30% when given concurrently to study subjects (n=16). An increase in the AUC of galantamine can increase the risk of acetylcholinesterase inhibitor-related adverse effects. One potential side effect of galantamine is bradycardia, which may increase the risk of QT prolongation. If the inhibitor being coadministered is also associated with QT prolongation (e.g., adagrasib, ceritinib, fluoxetine, ketoconazole, levoketoconazole, mifepristone), the risk of experiencing this adverse effect may be further increased.

MANAGEMENT: Caution and closer monitoring of the pharmacologic response to galantamine and its prodrug benzgalantamine is advised whenever a potent CYP450 2D6 and/or 3A4 inhibitor is added to or withdrawn from therapy. Some authorities suggest considering a reduction in the galantamine dose for patients on concurrent potent CYP450 2D6 and/or 3A4 inhibitors. Patients should be monitored more closely for acetylcholinesterase inhibitor related adverse effects including vagotonic effects on the heart rate (e.g., bradycardia, which may increase the risk of QT prolongation, and heart block), neurologic side effects (e.g., seizure activity), respiratory distress, bladder outflow obstruction, dizziness or syncope, nausea, vomiting and diarrhea. These effects may be more severe when the coadministered inhibitor shares a similar adverse effect profile with galantamine.