Short Ragweed
(Ambrosia Artemisiifolia)Short Ragweed Prescribing Information
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.
7. Skin tests should not be performed if the patient has taken antihistamine within 24 hours prior to testing.
Scratch Test: 1 drop of extract concentrate applied to a small scratch or scarification of the volar surface of the forearm or the flat aspect of the back.
A negative test shows only a slight red area at the site of scarification or prick penetration. Positive tests are scored as follows:
1+ Erythema with 5 mm wheal
2+ Erythema with 5 - 10 mm wheal
3+ Erythema with a 10 - 15 mm wheal
4+ Erythema with a wheal 15 mm (or larger) with pseudopodia
A negative test shows no change in the appearance and size of the 5 mm wheal created by the I.D. injection of 0.05 ml of extract. Positive tests are scored as follows:
1+ Erythema with 10-20 mm with a 5-10 mm wheal
2+ Erythema with 20-30 mm with a 5-10 mm wheal
3+ Erythema with 30-40 mm with a 10-15 mm wheal
4+ Erythema greater than 40 mm with a 15 mm wheal (or larger) with pseudopodia
Concentrated ragweed extract must be diluted before administration to new patients. As a rule, extract containing 0.01 to 0.05 units of antigen E per ml are safe to initiate immunotherapy. An intradermal skin test with the intended starting dose may be done as an additional precaution in evaluating the patient's sensitivity.
Injections should be given subcutaneously in the outer aspect of the upper arm. Care must be taken to avoid injecting the extract into a blood vessel, because of the potential hazard of anaphylaxis. Concentrated extract is usually administered once every two to four weeks at a maximum dose of 0.2 ml. A mild burning sensation immediately following the injection of concentrated extract is due to the glycerol in the extract. It should not be interpreted as an adverse allergic response. A suggested dosage schedule is shown in the Table below.
18.
Concentrated extracts (w/v 1:20) of short ragweed pollen usually contain between 100 and 300 units antigen E per ml. Mixed short-giant ragweed pollen extracts contain approximately one-half these values.
| AgE Units 0.01/ml frequency twice weekly | AgE Units 0.1/ml frequency twice weekly | AgE Units 1.0/ml frequency twice weekly | AgE Units 10/ml frequency twice weekly | AgE Units 100/ml frequency twice weekly |
|---|---|---|---|---|
| No. ml | No. ml | No. ml | No. ml | No. ml |
| 1 0.025 | 1 0.025 | 1 0.025 | 1 0.025 | 1 0.025 |
| 2 0.05 | 2 0.05 | 2 0.05 | 2 0.05 | 2 0.05 |
| 3 0.10 | 3 0.10 | 3 0.10 | 3 0.10 | 3 0.10 |
| 4 0.15 | 4 0.15 | 4 0.15 | 4 0.15 | 4 0.15 |
| 5 0.20 | 5 0.20 | 5 0.20 | 5 0.20 | 5 0.20 |
| 6 0.25 | 6 0.25 | 6 0.25 | 6 0.25 | 6 0.25 |
| 7 0.30 | 7 0.30 | 7 0.30 | 7 0.30 | 7 0.30 |
Note: Do not exceed a dose of 0.2 ml if the extract being administered contains 50% glycerol by volume
Studies
10, 11 have shown that the accumulated pre-seasonal dose of short ragweed pollen extract should be in the range of 250 to 1000 units of antigen E to effectively reduce ragweed-related symptoms
3, 19. This dosage of antigen E is contained in 2.5 ml to 10.0 ml of extract containing 100 antigen E units/ml. Treatment with a maximum tolerated dose is recommended for both short ragweed pollen extract and mixed short-giant ragweed extract.
The maintenance dose of ragweed pollen extract is defined as the highest tolerated dose that is consistently well tolerated without undue pain or swelling and which provides maximum relief to symptoms. The interval between maintenance injections should not exceed 4 weeks, since tolerance to the extract may be lost at longer intervals. If the interval exceeds 4 weeks, the dosage should be reduced by one-half for every additional two week period. A reduction in the maintenance dose also may be necessary during the ragweed season, due to the overdosing effects of inhaled allergen combined with injected allergen. As a rule, it is advisable to reduce the dosage by one-half during ragweed pollination and to increase the frequency of injections as needed to provide adequate relief symptoms. The dosage of ragweed pollen extract given to children is the same as the adult dose except for slight modifications due to body size and weight. A child's dose of 0.2 ml is considered comparable to an adult dose of 0.5 ml of the same dilution. Maintenance injection should be continued for a period of two to three years or longer, depending upon patient tolerance and clinical response.
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
- 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.
- In vitro studies with antigen E have shown that it is capable of causing histamine release from peripheral leukocytes of ragweed sensitive persons
1. - The antigen E content of short ragweed pollen extract has been found to correlate with extract potency when measured by skin test response in persons allergic to short ragweed pollen
2. - Immunotherapy with antigen E has been shown to be comparably effective to whole short ragweed pollen extract in reducing symptoms related to ragweed pollen exposure
3.
The weight by volume value shown on the label is a measurement of extract concentration, rather than extract potency. Weight by volume designations may be used to identify dilutions of extract for skin testing and immunotherapy, and are useful from a practical standpoint in identifying the relative strength of a given extract. However, studies have shown that the antigen E content varies in extracts with the same weight by volume concentration
4.
5, 6. The expiration period of aqueous concentrate and saline dilutions of glycerinated concentrate is approximately one-half that of glycerinated extract containing comparable antigen E content.
Ragweed extract should be kept at 2°C to 8°C during use and office storage to retain potency. Higher temperatures have an adverse affect on antigen E.
Short ragweed pollen extract and mixed short-giant ragweed pollen extract in concentrated form (w/v 1:20) are supplied in 1 ml dropper vials for scratch or prick testing and in 10 ml, and 50 ml vials for bulk use. Dilutions other than 1:20 w/v may be custom ordered.