Short Ragweed

INDICATIONS Studies have shown that properly performed an interpreted skin tests with ragweed pollen extract are useful in the diagnosis of allergy to ragweed pollen 7, 8, 20, 21 . Immunotherapy with the appropriate dosage of short ragweed pollen extract is effective in reducing symptoms of hay fever and asthma resulting from exposure to short ragweed pollen (9, 10, 11), and it is believed to be effective with extract of giant ragweed, although carefully controlled studies are unavailable. However, clinical observations and known cross reactivity between short and giant ragweed pollens have led to the practice of using a mixture of the two species for skin testing and treatment 22, 23, 24, 25, 26, 27 . This form of treatment is recommended for patients who cannot avoid exposure to pollen and who do not obtain satisfactory relief of symptoms from other medications, such as antihistamines. Immunologic changes resulting from treatment with short ragweed pollen extract are believed to include: The induction of specific anti-ragweed IgG antibodies commonly referred to as "blocking antibodies" 12, 13 . A decrease in the elevation of ragweed specific IgE during and immediately following the ragweed pollen season 14 . A reduction of circulating anti-ragweed IgE after long-term immunotherapy 15 . A decrease in skin reactivity to the extract 16 and a decrease in leukocyte sensitivity to histamine release 17 after long-term immunotherapy.

ADVERSE REACTIONS LOCAL REACTIONS. The occurrence of a hive 5 to 15 minutes after injection is usually due to leakage of extract into the skin along the needle tract. Firm pressure (not rubbing) at the site of injection immediately after withdrawal of the needle will usually prevent this reaction. It does not require a reduction in dosage. A strong local reaction with erythema and edema which persists at the injection site for several hours indicates that too much extract has been given. Failure to note this response may result in a serious generalized reaction. Treatment should be altered as follows: Additional injections should not be given until all evidence of the reaction has disappeared. The dosage should be reduced three levels, e.g., from 0.4 cc to 0.5 cc or the equivalent, and held at that level for two or three treatments. A second reaction at or near the dose which caused the first local response indicates that a maximum tolerated amount of extract has been reached and no further increases in dosage should be attempted. Maintenance therapy should be continued thereafter at the highest possible non-reacting dose. SYSTEMIC REACTIONS. Systemic (generalized) reactions may range from a mild exaggeration of the patient's allergic symptoms to hives, anaphylactic shock, or even death from anaphylaxis. Systemic reactions may occur when a previous local reaction has not been heeded, or when the extract is accidentally injected intravenously. The reaction usually occurs 5 to 20 minutes after injection. Symptoms may include sneezing, coughing, itching, shortness of breath, abdominal cramps, vomiting, diarrhea, tachycardia, hypotension, and respiratory failure in severe cases. The reaction is usually stopped by the subcutaneous injection of epinephrine HCL 1:1,000 (See Overdosage below). The oral administration of antihistamines and the placement of a tourniquet proximal to the injection site are helpful adjuncts. In the event that additional measures are required, it may be necessary to treat the patient for bronchospasm with intravenous aminophylline, intravenous fluids and corticosteroids; for hypotension with vasopressors, volume repletion, isoproterenol and corticosteroids; for laryngeal obstruction with oxygen and tracheostomy and for cardiac arrest with cardiopulmonary resuscitation and other appropriate measures.