We are independent & ad-supported. We may earn a commission for purchases made through our links.
Advertiser Disclosure
Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.
How We Make Money
We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently of our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.

What Are the Different Phenytoin Interactions?

By Susan Abe
Updated Feb 10, 2024
Our promise to you
WiseGeek is dedicated to creating trustworthy, high-quality content that always prioritizes transparency, integrity, and inclusivity above all else. Our ensure that our content creation and review process includes rigorous fact-checking, evidence-based, and continual updates to ensure accuracy and reliability.

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

Editorial Standards

At WiseGeek, we are committed to creating content that you can trust. Our editorial process is designed to ensure that every piece of content we publish is accurate, reliable, and informative.

Our team of experienced writers and editors follows a strict set of guidelines to ensure the highest quality content. We conduct thorough research, fact-check all information, and rely on credible sources to back up our claims. Our content is reviewed by subject-matter experts to ensure accuracy and clarity.

We believe in transparency and maintain editorial independence from our advertisers. Our team does not receive direct compensation from advertisers, allowing us to create unbiased content that prioritizes your interests.

Phenytoin is a common anticonvulsant medication used to control seizure disorders. The medication is structurally similar to major tranquilizers that may account for its commonly reported side effects of drowsiness and sedation. While phenytoin works primarily on the brain — reducing the excitability of the area that controls motor function — side effects from long-term use demonstrate a wide variety of effects on many body systems. Adding to the complexity of understanding this drug is the fact that phenytoin is strongly bound to serum protein, however, only the fraction that is "free" or unbound is pharmacologically active. Phenytoin interactions can occur anywhere within the drug's huge sphere of influence and include interactions with almost 1,000 other medications, foods and other diseases.

The most commonly reported phenytoin interactions are those with other medications. Almost 1,000 drugs reportedly have documented interactions with this anticonvulsant, including both over-the-counter and prescription drugs. Some common over-the-counter drugs that interaction with this drug include aspirin — which can increase drug levels in the body — and antacids which can have the opposite effect. Common prescription drugs with phenytoin interactions include diazepam, Lexapro® and furosemide.

Phenytoin interactions can be caused by interferences with absorption, contradictory actions, additive actions or even interruptions to serum protein levels. Indeed, reaching a therapeutic dosage for phenytoin is a balancing act that requires re-evaluation whenever a drug is added to, or removed from, a patient's usual regimen. Treatment recommendations for patients with an active seizure disorder include laboratory blood work testing for both total phenytoin levels and free phenytoin levels before the addition of a new medication. Follow-up testing is also recommended until therapeutic levels of phenytoin have stabilized. The same approximate procedure is recommended when a long-term drug is removed from a patient's medication regimen.

Foods are also indicated in some phenytoin interactions. Enteral feedings administered at the same time as phenytoin dosing can reduce the drug level in the system. Spicy foods that warrant over-the-counter antacids can also decrease phenytoin levels. Alcohol intake also has significant phenytoin interactions, causing increased or decreased levels depending upon whether the alcohol intake is acute or chronic.

Phenytoin interactions with other drugs, foods or compounds can be markedly increased by concomitant diseases. Anticonvulsants administration has been linked to onset of depression with suicidal tendencies or exacerbation of a preexisting depression. Patients suffering from diabetes mellitus can experience higher blood glucose levels with administration of phenytoin. Phenytoin's interference with vitamin D processing can cause conditions or injuries related to decreased skeletal density.

WiseGeek is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Discussion Comments
WiseGeek, in your inbox

Our latest articles, guides, and more, delivered daily.

WiseGeek, in your inbox

Our latest articles, guides, and more, delivered daily.