A person's A B O type depends upon the presence of absence of two genes --the A and B genes. These genes are encoded on chromosome 9. They determine part of the configuration of the red blood cell surface.
A person can be A, B, AB, or O. If a person has two A genes, their red blood cells are type A. If a person has two B genes, their red cells are type B. If the person has one A and one B gene, their red cells are type AB. If the person has neither the A nor B gene, they are type O.
The situation with antibodies in blood plasma is just the opposite. Someone with type A red cells has anti-B antibodies (antibodies directed against type B red cells) in their blood plasma. Someone with type B red cells has anti-A antibodies in plasma. Someone who is type O has both anti-A and anti-B antibodies in plasma. And someone who is type AB has neither anti-A nor anti-B antibodies in plasma.
It is most important to determine the A B O status of both donor and recipient in transplants and transfusions by typing and cross-matching. A B O incompatibility in such procedures can be a disaster.
The first recorded blood transfusion may have taken in 1492.
Tuesday, April 27, 2010
Sunday, April 18, 2010
Fexofenadine
Fexofenadine is an oral, "second generation" antihistamine that is used to treat the signs and symptoms of allergy that are due to histamine. It is similar to the other second generation antihistamines loratadine
Fexofenadine blocks one type of receptor for histamine (the H1 receptor) and thus prevents activation of H1 receptor-containing cells by histamine. Unlike the first generation antihistamines, fexofenadine and other second-generation antihistamines do not readily enter the brain from the blood, and, therefore, they cause less drowsiness.
Fexofenadine is used for the treatment of seasonal allergies and chronic urticaria (hives) in adults and children 6 years of age or older.
The most common side effects of fexofenadine are nausea, vomiting, weakness and sleepiness.
In controlled clinical studies there were no interactions with other drugs that significantly affected the safety or effectiveness of fexofenadine.
For seasonal allergies the recommended dose for adults and children 12 years or older is 60 mg twice daily or 180 mg once daily. Children 6-11 years of age should be given 30 mg twice daily. For chronic urticaria, adults and children 12 years or older should use 60 mg twice daily, and children 6-11 years of age should use 30 mg twice daily. Fexofenadine can be taken with or without food.
Fexofenadine blocks one type of receptor for histamine (the H1 receptor) and thus prevents activation of H1 receptor-containing cells by histamine. Unlike the first generation antihistamines, fexofenadine and other second-generation antihistamines do not readily enter the brain from the blood, and, therefore, they cause less drowsiness.
Fexofenadine is used for the treatment of seasonal allergies and chronic urticaria (hives) in adults and children 6 years of age or older.
The most common side effects of fexofenadine are nausea, vomiting, weakness and sleepiness.
In controlled clinical studies there were no interactions with other drugs that significantly affected the safety or effectiveness of fexofenadine.
For seasonal allergies the recommended dose for adults and children 12 years or older is 60 mg twice daily or 180 mg once daily. Children 6-11 years of age should be given 30 mg twice daily. For chronic urticaria, adults and children 12 years or older should use 60 mg twice daily, and children 6-11 years of age should use 30 mg twice daily. Fexofenadine can be taken with or without food.
