Friday, May 16, 2008

Loratadine (aka Alavert or Claritin): what is it and does it work?

Loratadine is classified in the second generation anti-histamine class of medications. Anti-histamine work by blocking the chemical called histamine from binding to its receptor and so preventing the "ON" signal for allergies to show up in a person. Histamine specifically causes itching of the eyes and skin or sneezing in the nose or coughing in the lungs, small blood vessels dilate and this is seen as swelling or congestion, and finally mucus production which is seen as the raised bumps of hives, watery eyes, runny nose, chest phlegm. The second generation class has 2 characteristics that distinguish them from first generation anti-histamine medications. First, second generation anti-histamines have a longer half-life, which means it will last longer. They usually need to be given only one to two times per day. Second, second generation anti-histamines normally do not cross the brain's special barrier on its blood vessels. This protects the brain from every substance in the blood. Some are toxic to brain cells. The first generation anti-histamines cross the brain's blood barrier and cause sleepiness, or tiredness, or difficulty concentrating, or a dry mouth. Second generation anti-histamines should not cause most people any tiredness.

Loratadine is effective in most people with allergic rhinitis (hay fever) at reducing the signs and symptoms of this disease. Studies show a benefit rate of about 67%. Note then, this means there is about 33% of people with allergic rhinitis who do not benefit from loratadine. We do not know why some people benefit and others do not. Now if a person develops severe allergic rhinitis, the signs and symptoms may appear not be affected, but in reality the loratadine is working. It is simply overwhelmed by the large amount of histamine being released. Think of it as being outgunned. To decrease symptoms, either you need to avoid the cause and wait for the disease to calm down, or you need to add more ammo to your side, that is take more allergy medications. A small number of people get tolerant to the positive effects of their medications. It appears as if the medicine does not work anymore or that they have become "resistant" to the medicine. Actually, yes, their immune system has changed slightly and so the same unchanged medication no longer is effective. In these cases, I recommend simply changing to another anti-histamine. Instinctively, nearly every one does this. Right? We just try another brand of antihistamine medication. Just be certain that the ingredients are not the same. Otherwise, except for the box and pill color, you have really changed nothing.

If you have any questions, ask your doctor.

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