Ambrosia Artemisiifolia

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.

There are no absolute contraindications to the use of ragweed pollen extract in the diagnosis and treatment of ragweed allergy. When used in accordance with accepted principles of skin testing and immunotherapy, the extract is considered safe and effective. Relative contraindications include (1) extreme sensitivity to the extract as demonstrated by previous anaphylaxis following skin testing or subcutaneous injection, (2) recent myocardial infarction, and (3) pregnancy (see Precautions #4). The benefit to risk ration must be evaluated in each of the above situations. Ragweed pollen extract should not be administered to persons who are not sensitive to ragweed pollen

Physicians who elect to administer ragweed pollen extract should be familiar with the clinical use of allergenic extracts and have the necessary emergency equipment and medication available to treat systemic allergic reactions. The injection of ragweed pollen extract may cause severe local and/ or systemic anaphylactic reactions in some individuals. To minimize this potential hazard, the relative sensitivity of the patient must be assessed from the allergic history and from clinical observations. Patients should be informed of this risk prior to skin testing and immunotherapy (see adverse reactions). The dosage must be reduced when starting a patient on fresh standardized (Antigen E) extract or when transferring a patient from non-standardized to standardized extract, even though the labeled strength of the old and new vials may be the same. This is necessary due to a loss of extract potency during storage in the physician's office. The antigen E content of old and new extract must be compared and adjusted by dosage reduction and/or dilution before new extract is administered. The amount of new extract given from the old vial, assuming both extracts contain comparable amounts of antigen E. Any evidence of a local or generalized reaction requires a reduction in dosage during the initial stages of hyposensitization as well as during maintenance therapy.

Extract must be stored at 2°C to 8°C to retain potency. Storage at this temperature should be observed as closely as possible, since higher temperatures adversely affect the antigen E content of the product. Extract should not be left at room temperature for the purpose of making dilutions or mixing with other allergenic materials, unless precautions are taken to maintain the recommended temperature using special cooling trays or other suitable methods. Extract should be administered with autoclaved or sterile disposable syringes, needles and testing devices to prevent the transmission of homologous serum hepatitis and other infectious agents from person to person. Extract may cause local or generalized reactions. Physicians who administer the product should be familiar with the principles and practice of allergy and should have epinephrine HCL 1:1,000, as well as other emergency medication and equipment available to treat anaphylaxis. Persons receiving extract by skin test or by subcutaneous injection for treatment must be instructed to remain in the physician's office for 20 minutes following testing or immunotherapy, and to return immediately to the office if any signs of a generalized allergic reaction occur, including hives, symptoms of hay fever, and/ or asthma. PREGNANCY CATEGORY C. ragweed pollen extract. Animal reproduction studies have not been conducted with ragweed pollen extract. It is also not known whether ragweed pollen extract can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity. Ragweed pollen extract should be given to a pregnant woman only if clearly needed.

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.