Anti Allergic Medicines Information

Allergy Medicine

Allergy means excessive or over sensitivity to a substance. The provoking substance is known as an allergen which can be a drug, food and inhalants. This allergen is having potential to cause hypersensitive response in the body. When first exposure occurs with the allergen, the body forms antibodies against the substance and when the exposure occurs for the second time or onwards there is antibody reaction which appears in the body. This reaction is characterized by histamine release causing flushing, itching, hypotension and respiratory reactions like asthma. Pain is caused by prostaglandins and the activity of smooth muscles increases. This is the cause why heart beats more faster as it consists of smooth muscles. In order to treat the allergic reactions, various category of allergy drugs have been formulated.

In response to allergy histamine is released in the body. To prevent severe or fatal response of histamine, it is opposed in three ways. By using drugs causing opposite reaction to the action of histamine, by preventing histamine release i.e. use of steroids, and finally, by slopping the histamine to reach the affected site i.e. H1 and H2 receptor antagonists or antihistamine prevent the itch and flare. It also prevents the smooth muscle contractions, partially.

Histamine antagonists are of two types H1 receptor antagonists and H2 receptor antagonists. H1 antihistamines are used specially for allergies. They oppose the action of histamine and stops the edema formation and violent reactions. These are further classified into sedative and non sedative types. Sedative anti histamine drugs caused drowsiness and patient con\\\'t do driving or activity after taking it. They do not enter the brain, mequitazine, chlospheniromine, diphenyhydramine, promethazine, hydroxizine, ethanolamines, piperzines, include meclozine, cinnarizine.

The newer antihistamines are H1 receptor, non sedating antihistamines. These are better than previous antihistamines as they can enter the brain and act quickly. They are cetrizine, terfenadine these are given once daily and are more stronger and effective; Astemizole it is having slower effect. Antihistamines can be classified on the their location of action. Those actingon central nervous system and others acting on peripheral nervous system. Action of H2 antihistamine include stimulation of cardiac rate or heart rate, inhibition or prevention of contraction of muscles of uterus, increase of acid in stomach and dilation of blood vessels. Allergy can cause fall in blood pressure.

At that time, the patient needs both H1 and H2 receptor antagonists as both receptor are responsible for lowering blood pressure. Acrivastine - kept for intermittent, moderate therapy, for hay fever, these are given once daily and are more