Those who suffer from various types of seizure disorders may experience an adverse reaction to Dilantin—also known generically as phenytoin.

This adverse reaction to Dilantin is connected to high or toxic levels of the medication, according to the Epilepsy Foundation. At an unusual level, it can actually interfere with the communication function of healthy nerve cells.

Although discovered as early as 1908, it wasn’t until 1936 that Dilantin was found to be useful in the treatment of seizures. It was first used to control convulsant activity secondary to electroshock treatments.

As indicated by Everyday Health, it wasn’t until 1953 that it was approved by the U.S. Food and Drug Administration for commercial distribution by a doctor’s prescription.

Phenytoin is rarely a first choice treatment by doctors specializing in the treatment of seizure disorders. Still, it is considered the “grandfather” of other more modern medications for epilepsy. The Epilepsy Foundation considers it best used for partial-onset seizures but ineffective against generalized-onset absence seizures or infantile spasms.

When still employed, dosage levels and length of treatment should be carefully monitored to avoid the adverse reaction to Dilantin known as cerebellar atrophy or ataxia.

Cerebellar Atrophy

According to the Mayo Clinic, the cerebellum is comprised of two ping-pong ball sized lobes of neurological tissue that are located at the base of the brain near the brain stem. The biggest job that this area of the brain performs is the coordination of movement between several areas of the body.

The U.S. Department of Health and Human Services has identified a key symptom of cerebellar atrophy as a lurching type of walk which is wide-based—the legs are spread quite far apart—and they move in an uncoordinated fashion.

This walk is frequently accompanied by a side-to-side tremor of the trunk. Other signs include odd, uncontrollable eye movements known as nystagmus and slurred speech. It is not uncommon for an untrained person to assume a sufferer is inebriated.

The 1994 Study

It is important to note that seizure disorders in and of themselves are associated with a smaller than average cerebellum. This is the effect of the disease. In 1994, a study was undertaken in which all enrollees has seizure disorders and half were treated with phenytoin and half were treated with another medication.

Cerebellum size was assessed in all patients at the beginning and end of the study. It was determined that overall shrinkage of the cerebellum was exacerbated further by long-term Dilantin use.

Osteomalacia

In addition to cerebellar atrophy, another adverse reaction to Dilantin use over the long term is osteomalacia. Osteomalacia is a gradual softening of the bones which is usually attributed to Vitamin D or calcium deficiency.

Patients taking the medication are encouraged to maintain an active exercise regimen, eat healthy and include foods rich in calcium and vitamin D. Supplementation is also recommended.