Often doctors find that medicines are useful for more than one purpose. It is legal to prescribe medicines for "off-label uses" even though the FDA has not formally approved such use. Common off-label uses of Phenytek include:

1. Treating a type of facial pain called trigeminal neuralgia. Phenytek's effectiveness for this purpose has not been proven, however, and carbamazepine (Tegretol, Carbatrol) should be considered the first choice. Phenytek may be added if carbamazepine is not effective.
2. Treating nerve disorders like diabetic neuropathy and Fabry's disease. Phenytek seems to be only slightly effective but it may help other pain-relieving medications.
3. Treating certain psychiatric disorders, such as the mania of bipolar disorder. Few studies have shown a definite benefit, however. Another reason for caution in this kind of use is that Phenytek interacts with many of the medicines generally used to treat psychiatric disorders.