Can you take phenytoin before surgery? A patient's guide

According to UK clinical guidelines, patients should be advised to continue their regular medications, including phenytoin, on the day of surgery unless specifically instructed otherwise by their doctor. This is because managing your anti-seizure medication is a critical aspect of surgical preparation, requiring careful coordination with your healthcare team to ensure a safe procedure and prevent complications.

Quick Summary

Managing phenytoin before surgery is a critical process involving close coordination with healthcare providers. The medication is typically continued, often taken with a small sip of water early on the day of surgery, to prevent dangerous withdrawal seizures. Intravenous alternatives are available if oral intake is restricted.

Key Points

• Do not stop abruptly: Abruptly stopping phenytoin can lead to severe withdrawal seizures, including status epilepticus.

• Always consult your doctor: Never make a change to your medication schedule for surgery without explicit instructions from your healthcare team.

• Oral dose with small water: For many procedures, you can take your morning dose with a minimal amount of water, up to two hours before surgery.

• Intravenous alternative exists: If you cannot take oral medication, an IV form of phenytoin can be administered during or after surgery.

• Be aware of drug interactions: Phenytoin can interact with anesthetic agents and other medications, and your medical team must be aware of your regimen.

• Communicate with your team: Your neurologist, surgeon, and anesthesiologist should coordinate to create a safe medication plan.

• Understand special monitoring: In some cases, like a long ICU stay, your phenytoin levels may need to be monitored closely.

Why Continuing Phenytoin is Crucial

The primary reason for continuing phenytoin and other anti-epileptic drugs (AEDs) before surgery is to maintain consistent therapeutic drug levels in the bloodstream. Abruptly stopping or skipping a dose of phenytoin can significantly decrease its concentration, potentially triggering withdrawal seizures or, in severe cases, a life-threatening condition called status epilepticus. The consistent presence of the medication is essential to keep neurological conditions, like epilepsy, under control during the stressful perioperative period.

The risks of abrupt withdrawal

Abruptly stopping phenytoin, a practice that is strongly discouraged, can lead to several dangerous outcomes:

• Status Epilepticus: A life-threatening emergency characterized by continuous seizures or repeated seizures without recovery.
• Loss of Therapeutic Control: The steady-state level of the drug is lost, making the patient vulnerable to seizure activity.
• Other withdrawal symptoms: These can include lethargy, tremor, nausea, and vomiting.

Preoperative Medication Management Strategies

Careful planning is required to ensure a patient receives their necessary dose of phenytoin while adhering to the standard 'nothing by mouth' (NPO) instructions before surgery. The strategy depends on the type and duration of the procedure.

• Oral Administration: For many outpatient or shorter procedures, a patient can take their medication early in the morning with a small amount of water, typically up to two hours before surgery. The volume of water is minimal and does not pose a significant aspiration risk.
• Intravenous (IV) Conversion: For prolonged surgeries or when a patient cannot take oral medication postoperatively (due to being on a ventilator or having abdominal surgery), the team may switch to an intravenous form. Phenytoin is available in an IV formulation, making it a viable option for perioperative management. This transition requires careful monitoring to ensure therapeutic levels are maintained.

Potential Drug Interactions with Anesthesia

Phenytoin is a potent inducer of hepatic cytochrome P450 enzymes. This enzyme induction can significantly speed up the metabolism of other drugs, including those used in anesthesia, potentially reducing their effectiveness. Anesthesiologists must be aware of a patient's phenytoin use to adjust dosages accordingly. Key interactions to consider include:

• Neuromuscular Blockers (NMBAs): Acute administration of phenytoin can augment the effect of non-depolarizing NMBAs, potentially prolonging their effects and delaying recovery from anesthesia.
• Opioids: Phenytoin can increase the metabolism of certain opioids, like morphine, potentially reducing their pain-relieving effects.
• Local Anesthetics: Coadministration with local anesthetics can increase the risk of methemoglobinemia in susceptible individuals.

Comparing Perioperative Management Options

Feature	Oral Administration	Intravenous (IV) Conversion
Patient Suitability	Short procedures, no anticipated swallowing difficulties, clear liquids allowed until 2 hours before.	Prolonged surgeries, patients unable to swallow, critically ill patients, or extensive post-operative NPO periods.
Administration Method	Taken with a small amount of water in the morning before surgery.	Administered via an IV drip, typically starting intraoperatively or postoperatively.
Risks	Minimal aspiration risk if managed properly. Potential for missed dose if not taken correctly.	Cardiovascular side effects if infused too rapidly. Potential for extravasation at the injection site.
Monitoring	Less intensive monitoring needed if patient is stable.	Requires close monitoring of serum drug levels, especially in an ICU setting.
Logistical Challenge	Straightforward, requires patient compliance.	Requires IV access and careful calculation of loading and maintenance doses.

The Role of the Multidisciplinary Team

Effective perioperative care relies on a team approach involving several specialists. The neurologist who manages the patient's epilepsy is best equipped to advise on the patient's medication regimen and seizure control. They should communicate with the surgeon and anesthesiologist to devise a plan that minimizes seizure risk and avoids adverse drug interactions during the procedure. For complex cases, involving the neurologist directly is highly recommended to determine the best course of action.

Conclusion: The Importance of Communication and Planning

In conclusion, the question, "Can you take phenytoin before surgery?" is most often answered with a definitive "yes," provided the patient and medical team follow a carefully considered plan. The risks of sudden withdrawal are far greater than the risks associated with taking a scheduled dose. The specific management strategy—whether oral administration with a small amount of water or a switch to an IV formulation—will be tailored to the patient's individual needs, the type of surgery, and the anticipated postoperative course. Patients should always proactively inform their healthcare providers about their medication history and adhere strictly to the plan devised by their multidisciplinary care team. Resources such as the Epilepsy Foundation provide valuable patient education on this topic. Learn more about managing epilepsy medications during surgical procedures on the Epilepsy Foundation website: https://www.epilepsy.com/tools-resources/seizure-medication-list/phenytoin.

References

• Common questions about phenytoin - NHS
• Phenytoin - UKCPA - Handbook of Perioperative Medicines
• GUIDELINES FOR ANESTHESIA AND SURGERY IN PEOPLE WITH ...
• Phenytoin - Epilepsy Foundation
• Phenytoin: MedlinePlus Drug Information
• Anaesthesia and epilepsy | BJA - Oxford Academic
• If a patient must limit food/water prior to surgery, when and ...
• Delayed recovery from anaesthesia due to acute phenytoin ...
• Drug Interactions: Chirocaine, phenytoin - Drugs.com
• Morphine and phenytoin Interactions - Drugs.com

Frequently Asked Questions

Can I skip my phenytoin dose if my surgery is in the morning?

No, you should never skip your phenytoin dose. Abruptly stopping the medication can lead to dangerous withdrawal seizures. Your doctor will provide specific instructions on how and when to take your dose on the morning of surgery.

What if I'm not allowed to eat or drink before surgery?

You can typically take your medication with a very small sip of water, often up to two hours before surgery. For longer fasting periods or more extensive surgeries, your doctor may arrange for you to receive an intravenous (IV) version of phenytoin.

Does phenytoin interfere with anesthesia medications?

Yes, phenytoin can interact with certain anesthetic agents because it speeds up the metabolism of other drugs in the body. This is why it is critical to inform your anesthesiologist about all medications you are taking so they can adjust their dosage accordingly.

Who should I talk to about my phenytoin management before surgery?

You should inform your entire healthcare team, including your surgeon, anesthesiologist, and the nurse involved in your preoperative preparation. It is especially important for your neurologist to be in the loop and coordinate with the rest of the team.

What happens if I forget to take my dose on surgery day?

If you forget your dose, you should inform your doctor or nurse immediately. They will assess the situation and determine the safest course of action, which may include administering an IV dose to prevent seizure activity.

Is it safe to switch from oral to IV phenytoin?

Switching from oral to IV phenytoin is a standard procedure in perioperative care when oral intake is restricted. It must be done under strict medical supervision and requires careful monitoring of drug levels to ensure safety and effectiveness.

When can I restart my normal phenytoin schedule after surgery?

Your doctor will provide instructions on when to resume your oral medication schedule. For some, it may be as soon as they can safely swallow, while others who receive IV therapy may need a longer transition period.

Can phenytoin cause complications during surgery?

While generally safe under medical supervision, phenytoin can affect the metabolism of other drugs. Potential complications can arise from drug interactions, but these are manageable when your healthcare team is fully informed.