PHARMACOTHERAPY OF PERENNIAL AND SEASONAL ALLERGIC RHINITIS

The options for pharmacotherapy of both perennial and seasonal allergi c rhinitis continue to expand rapidly. The classic antihistamines will retain a place as effective drugs. They are without serious adverse e ffects, and are often available without a physician's prescription. Th e newer antihistamines, such as terfenadine, astemizole, loratadine an d cetirizine, have made a great impact because they are, for the most part, nonsedating and have little or no anticholinergic activity. They have few interactions with other drugs and, except for very specific limited interactions, have proven to be well tolerated by patients pre viously unable to use antihistamines. Some of the newer antihistamines are also antiallergic by mechanisms other than H-1-receptor antagonis m which will expand their usefulness. Corticosteroids may be used as o ral or intranasal preparations, The most frequently used preparations are beclomethasone, triamcinolone, budesonide and fluticasone. Cortico steroids are anti-inflammatory agents, and primarily protect against t he late allergic response. Decongestants produce symptomatic relief bu t are not antiallergic, acting only on the target organ. Mast cell sta bilisers were the first agents to improve both the immediate and late allergic responses. Intranasal sodium cromoglycate (cromolyn sodium) w as the first available, being quite effective but requiring frequent a dministration. Intranasal nedocromil has several different mechanisms of action, including stabilising cell membranes and preventing mediato r release. New oral preparations, such as ketotifen, may eventually be of benefit. Other agents, such as mucolytics and anticholinergics, ar e still under development; all improve the symptoms of allergic rhinit is by a variety of mechanisms.