What Factors Affect a Sufficient Phenytoin Dose?

The best phenytoin dose is largely dependent on how the patient responds to the anti-seizure medication. It may take several weeks to find the optimal dose for a patient, and constant monitoring can be required to make sure the drug is still meeting the patient’s needs. Patients in treatment for seizures may take multiple medications in addition to making lifestyle adjustments to reduce the frequency and intensity of seizures.

Patients slowly increase the phenytoin dose over time, with guidance from a medical provider. This can prevent complications associated with taking a high dose too quickly, which could increase the risk of experiencing seizures. The goal is typically to bring the patient up to a base dose of 300 milligrams per day, so the patient’s response to the drug can be assessed. If the patient does well, the three divided doses may be switched to one extended-release dose to make it easier to take the medication. Two indicators can help a medical provider determine if the patient is going well on the drug.

Decreased seizure activity is a good sign, as it indicates the drug is effectively suppressing seizures. Additionally, the doctor can request a check of the serum levels of the medication to determine the concentration in the blood. If these are low, the patient’s seizures may only be partially controlled, and could break through under stress even though the patient is on medication. Increasing the phenytoin dose may be necessary if the patient continues to have seizures or has unusually low serum levels.

As the dosage increases, patients need to be alert to side effects like increased seizure activity. Blood testing can also check for problems like liver damage, a known potential side effect of the medication. Patients who react poorly to the drug may need to explore an alternative medication that could be safer and just as effective. If a switch is necessary, the phenytoin dose needs to be slowly decreased, allowing the patient to adjust to living without it, before introducing a new drug. Abruptly stopping can cause severe seizures.

Some cases may call for a very high loading phenytoin dose when a patient experiences severe seizures and needs immediate treatment. The appropriateness of such dosing can depend on a patient’s medical history, a doctor’s experience, and the situation. Such patients may need to be carefully monitored for signs of adverse reactions, and they should follow directions about how and when to take the medication to avoid complications.