Dear Dr. Gott: Our son, now 47, was severely brain injured in a bike accident 28 years ago. As a result, he also suffered grand mal seizures. He was put on 100 milligrams of Dilantin twice a day. It was then increased to three times daily. He has been seizure-free for almost 20 years now. My son is otherwise very healthy. He lives with us but has become quite independent and even drives his own car.

Our family physician retired, and our new (young) family physician said the decision was ours, but we should think about stopping the medication. We're hesitant because we dread the possibility of seizures again. What are your views on this situation?

Reply: Most neurologists I know often remove patients from Dilantin if they have been seizure-free for several years. This must be done by gradually reducing the dose and must be supervised by a neurologist. Only this type of specialist can tell you whether it is appropriate to discontinue the Dilantin.

You and your son need to speak to his neurologist about the possibility of stopping the medication, and the possible risks and benefits of stopping versus continuing the medication.

If the specialist believes it is best to stop the medication, he or she may recommend testing before, during and/or after the process. This will provide appropriate monitoring of your son for any adverse effects from stopping the Dilantin, such as return of the seizures or abnormal brain function.

I am not a neurologist and am not familiar with your son's case. His neurologist is his best source for further information.

Dear Dr. Gott: What medical information is obtained from a blood gas? What symptoms indicate that a blood gas be performed on a patient?

Dear Reader: An arterial blood gas measures the acidity of the blood, as well as the amount of oxygen, carbon dioxide and other gases. The test is used primarily for evaluation of patients who are unable to breathe properly and maintain normal pulmonary functions.

If the oxygen level is down and the carbon dioxide is elevated, aggressive therapy is required. This generally includes nebuliser treatments, supplemental oxygen, inhalers and more. It is also vital to find the cause of the breathing difficulties. Pulmonary disorders are one of the most common, but heart failure, drug overdose, kidney failure and other severe stress disorders may also cause an abnormal blood-gas level.

Patients who have serious lung disorders, such as chronic obstructive pulmonary disease (COPD), often require supplemental oxygen 24 hours a day. A blood gas is important in this instance to ensure that the patient is responding appropriately and is receiving a proper amount of oxygen.

To give you related information, I am sending you a copy of my Health Report "Pulmonary Disease." Other readers who would like a copy should send a long, self-addressed, stamped envelope and $2 to Newsletter, PO Box 167, Wickliffe, Ohio 44092. Be sure to mention the title.

Doctor Gott is a retired physician and the author of the book "Dr. Gott's No Flour, No Sugar Diet," available at most chain and independent bookstores, and the recently published "Dr. Gott's No Flour, No Sugar Cookbook."