Dilantin (phenytoin) has been linked to an increased risk of cerebellar atrophy ataxia, a disorder marked by lost neural connections in the brain.

Cerebellar atrophy ataxia involves loss of neural connectivity in the cerebellum, the part of the brain that controls speech and movement. As the cerebellum atrophies, the degeneration causes that part of the brain to shrink.

About Dilantin

Patients take Dilantin (phenytoin) to control epileptic seizures, partial tonic clonic seizures, and complex partial seizures. Dilantin also might be prescribed to prevent seizures after a patient undergoes certain types of neurosurgery. Currently, well over 2 million people in the U.S. are prescribed Dilantin according to the ClinCalc Drug Stats Database.

The medication was first developed by a German chemist in 1908, who sold the patent to Parke-Davis (now a division of Pfizer). However, it was 30 years before it was discovered to be useful for preventing seizures.

Prior to that time, people who were prone to seizures were given potassium bromide (used today in veterinary medicine to treat seizures in dogs) and phenobarbital. Dilantin was approved by the FDA for the treatment of epileptic seizures in 1953.

Other Indications for Dilantin

In addition to treating seizures, Dilantin may be prescribed for some heart conditions, such as rapid or irregular heartbeat. It is also indicated for a condition known as trigeminal neuralgia, according to the Mayo Cinic, a condition affecting the nerves connecting facial tissues and muscles to the brain, causing bouts of severe pain.

Symptoms of Cerebellar Atrophy Ataxia

A patient may suffer from a variety of different symptoms of cerebellar atrophy as a result of Dilantin toxicity. Among the most common indications of cerebellar ataxia are:

• Problems walking/posture issues. Patients may exhibit an unnaturally jerking gait, an uncoordinated walk that may make them appear to stagger. Advanced ataxia symptoms may include tripping, falling, inability to safely navigate stairs or an inability to maintain an upright posture.
• Speech and swallowing problems. Speech may become slow or even slurred. The patient also might have a hard time swallowing foods because they choke easily, particularly when attempting to swallow liquids.
• Impaired fine motor skills. Depending on the severity of the cerebellar atrophy ataxia, the patient may have difficulty writing, typing, dialing a phone or performing other tasks that require fine motor skills.
• Severe fatigue. Performing everyday tasks can cause patients suffering from cerebellar atrophy to tire easily. Many patients report feeling they need to think about their movements to perform tasks that once seemed easily coordinated and second-nature to complete, such as brushing their teeth, buttoning their clothes and navigating stairs.
• Cognitive impairment. In some cases, patients with cerebellar degeneration may experience problems recalling newly given information. They also might have difficulty formulating a plan or keeping their thoughts in logical sequence.
• Visual disturbances. Patients may suffer from abnormally quick, uncontrolled eye movements, which is a condition called nystagmus. Blurred vision or double vision is possible, as well. Reading becomes harder as the eyes cannot follow the left to right progression of text.
• Mood problems. Dilantin toxicity that causes cerebellar degeneration can result in personality changes and mood disorders. Irritability, anxiety, and depression are among the issues people with cerebellar deficiencies experience more often than people who have healthy cerebellums.

Even though seizures themselves can cause brain disturbances that result in cerebellar atrophy, studies have taken this into account and determined that Dilantin is an additional risk factor.

Patients on long-term Dilantin therapy and those who have taken doses above the therapeutic range are particularly at risk of cerebellar atrophy, but even some who have had blood levels within the normal therapeutic range have suffered brain degeneration.

More Dilantin Side Effects

Aside from cerebellar atrophy ataxia, Dilantin also has been linked to other serious health consequences. These include
decreased bone density, overgrowth of the gums and nerve damage that leads to pain or numbness in the extremities.

A small number of patients also are susceptible to Stevens-Johnson Syndrome (SJS) after taking Dilantin. SJS is a severe allergic reaction that causes open sores on the skin and in the mucous membranes and makes the patient vulnerable to serious infections.

Other side effects include hypotension (abnormally low blood pressure), nystagmus (uncontrolled, spasm-like eye movement) and nerve damage. It also inhibits the body’s ability to absorb folate, a necessary nutrient found in leafy greens and several other foods. Folate deficiency can impair the production of red and white blood cells, leading to serious anemia and other problems.

Dilantin is not recommended for women during pregnancy, as it has been associated with fetal injuries similar to fetal alcohol syndrome.

According to the label, Dilantin also been associated with an autoimmune condition known as lupus and may cause depression or suicidal thoughts in some patients.