Drug Interactions between Phenytoin Sodium, Extended Release and upadacitinib

Consumption of grapefruit, grapefruit juice, and supplements that contain grapefruit should be avoided during treatment with upadacitinib as they may increase the blood levels of upadacitinib, which may increase the risk and/or severity of side effects such as low blood cell counts, anemia, serious infections, and elevated blood lipid levels. Contact your doctor if you develop symptoms such as paleness, fatigue, dizziness, fainting, fever, chills, diarrhea, sore throat, muscle aches, shortness of breath, blood in phlegm, weight loss, red or inflamed skin, body sores, or pain or burning during urination.

Smoking during treatment with upadacitinib may increase your risk of serious cardiovascular events and of developing malignancies. Tell your doctor if you are a current or past smoker. Talk to your doctor if you have any questions or concerns. Get emergency help right away if you develop any symptoms of a heart attack or stroke during treatment with upadacitinib, including severe tightness, pain, pressure, or heaviness in your chest, neck, or jaw; weakness in one side of your body; slurred speech; shortness of breath or feeling lightheaded. 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.

Phenytoin levels may decrease when the suspension is given with enteral feedings. This could lead to a loss of seizure control. You could interrupt the feeding for 2 hours before and after the phenytoin dose. Alternatively, you may give the phenytoin suspension diluted in water and flush the tube with water after administration. These would make it easier for your body to absorb the medication. However, this still may not entirely avoid the interaction and may not always be feasible. You should have your phenytoin levels checked upon starting and stopping of enteral feedings. In addition, using phenytoin together with food may alter the effects of phenytoin. Contact your doctor if you experience worsening of seizure control or symptoms of toxicity, including twitching eye movements, slurred speech, loss of balance, tremor, muscle stiffness or weakness, nausea, vomiting, feeling light-headed, fainting, and slow or shallow breathing. If your doctor does prescribe these medications together, you may need a dose adjustment or special test to safely use both medications. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Ask your doctor before making any changes to your therapy.