Common side effects of Tegretol include dizziness, drowsiness, unsteadiness, vomiting, diarrhea, constipation, stomach pain, confusion, headache, blurred vision, ringing in the ears, dry mouth, swollen tongue, and leg cramps.: Tegretol (carbamazepine) belongs to a class of drugs called anticonvulsants or anti-seizure medications. It works by decreasing nerve impulses that cause seizures and pain. Tegretol is used to treat seizures, bipolar disorder, and nerve pain, such as trigeminal neuralgia and diabetic neuropathy.