Drug Interactions between isocarboxazid and phenytoin

During and within two weeks after treatment with isocarboxazid, you must not consume any foods or beverages that are high in tyramine content. Doing so can raise your blood pressure to dangerous levels, a condition known as hypertensive crisis. The condition is potentially fatal and may cause symptoms such as severe headache, confusion, blurred vision, problems with speech or balance, nausea, vomiting, chest pain, convulsions, and sudden numbness or weakness (especially on one side of the body). You should seek immediate medical attention if you have any of these symptoms. Foods that are high in tyramine include, but are not limited to, air dried meats; aged or fermented meats; sausage or salami; pickled herring; anchovies; liver; red wine; beer; aged cheeses, including blue, brick, brie, cheddar, parmesan, romano, and swiss; sour cream; sauerkraut; canned figs; raisins; bananas or avocados (particularly if overripe); soy beans; soy sauce; tofu; miso soup; bean curd; fava beans; or yeast extracts (such as Marmite). You should avoid the use of alcohol while being treated with isocarboxazid, as alcohol may increase some of the nervous system side effects such as dizziness, drowsiness, and difficulty concentrating. Also avoid activities requiring mental alertness such as driving or operating hazardous machinery until you know how the medication affects you. Talk to your doctor or pharmacist if you have any questions or concerns.

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.