Q I have been taking cross-country airline flights for business and pleasure for several years and never experienced any physical difficulty because of it. Now I hear that people who take long flights could become victims of dangerous blood clots that form in their legs as a result of sitting in one place too long. What is this all about? And do I now have another reason to be afraid to fly? T.P., Atlanta

A The condition you are talking about is often referred to as “economy-class syndrome,” and it can cause some serious problems, doctors say. “Economy-class syndrome” refers to the relatively cramped seating space that airline passengers in the main cabin have to deal with. Because the tight quarters generally restrict one’s maneuverability, it can cause circulatory problems.

While the legs are pressed against the edge of the seat during long flights, the pressure behind the knee can affect circulation and possibly promote clotting. The danger is that clots can form a blockage in a blood vessel and if the clot breaks free, it can travel to the lungs and heart, blocking an artery. Doctors says such a condition can be fatal.

During long flights, medical experts suggest that airline passengers try to prevent clotting by flexing the knee periodically or frequently wiggling the feet and toes to promote continuous proper circulation. While the seat-belt light is turned off, it’s also a good idea to get out of your seat and walk around to ensure proper blood flow.

Q I take quite a bit of medication for a variety of medical problems, and the drugs I have to take are very expensive. I’ve never thought about asking my doctor to prescribe generic drugs because I didn’t know if they would be as effective. What is the difference between generic and brandname drugs? M.N., Minneapolis

A Other than name and price, there’s not much difference between a generic and brand-name drug. A generic drug is known by its chemical name and a brand name is what the manufacturer calls the drug.

The products have the same ingredients. Generic drugs must have the same active ingredients, strength, and dosage form–pill, liquid or injection. But before generic drugs are approved, they must not only have identical active chemical compounds as brandname drugs, but the quantity and speed of absorption of its ingredients into the bloodstream must also be the same or similar.

Typically, generic drugs are less expensive than brand-name drugs. They can cost substantially less than their counterparts because the companies that make them don’t have to recover the costs of research and development, doctors say.

Talk to your doctor to see if generic drugs are right for you. All drugs don’t have generic equivalents, but pharmacists can compare and evaluate generic and brand-name drugs, and in consultation with your doctor, they can provide the right medication at the best possible price.

`BRAIN FREEZE’

Q Since I was a child I have wondered why you can get a painful headache when you drink something very cold or eat ice cream too fast. Can you explain what’s going on when this happens and if this condition can cause any lasting effects? E.G., Washington, D.C.

A All of us have experienced what is commonly known as “brain freeze,” which really is the dialtion of blood vessels in the roof of your mouth–widening them to allow more warm blood to the area. Doctors say the headache is referred pain carried from the nerves in your mouth through branches of one of your cranial nerves. Those branches transmit the pain and it’s manifested as a headache.