For subcutaneous use only.
Subcutaneous injections for immunotherapy are prepared by diluting the stock concentrate. See Table 1 for instructions regarding dilution and preparation.
Administration
Administer immunotherapy by subcutaneous injection in the lateral aspect of the arm or thigh. Do not inject directly into any blood vessels.
Observe patients for at least 30 minutes as most adverse reactions occur within 30 minutes after injection.23
Dose Build-up
Dosing of Standardized Grass Pollen Extracts for allergen immunotherapy is highly individualized. The initial dose is determined by the patient’s percutaneous skin test reactivity and clinical history. The initial dose is typically 0.05 mL of a 0.01 BAU/mL dilution for standardized Bermuda grass pollen extract and 0.05 mL of a 0.1 BAU/mL dilution for all other Standardized Grass Pollen Extracts. In patients who appear to be exquisitely sensitive by skin test and history, consider a lower initial dose. The dose is increased at each injection by no more than 50% of the previous dose, and the next increment is governed by the response to the last injection. Dosing is increased in increments until 0.5 mL is reached, following which 0.05 mL is administered from the next most concentrated allergen extract or allergen mixture vial in the dilution series. Injections are typically given one or two times per week until the maintenance dose is reached.
- Any evidence of a systemic reaction to immunotherapy is an indication for a significant reduction (at least 75%) in the subsequent dose or the cessation of immunotherapy. Proceed cautiously in subsequent dosing if immunotherapy is continued.
- Repeated systemic reactions, even of a mild nature, are sufficient reason for the cessation of further attempts to increase the reaction-causing dose.
- The volume of solution for immunotherapy may produce increased discomfort in pediatric individuals. In order to achieve the total dose required, the volume of the dose may be divided into more than one injection per visit.23
Maintenance Dose Selection and Intervals
Select a maintenance dose based on the patient's clinical response and tolerance.
- Typical maintenance dose is 300-1,500 BAU for Standardized Bermuda Grass and 1,000-4,000 BAU for all other Standardized Grass Pollens.23 Occasionally, higher doses are necessary to relieve symptoms.
- Northern prairie grasses (Kentucky Blue [June], Meadow Fescue, Orchard, Perennial Rye, Redtop, Sweet Vernal, and Timothy) are highly cross-reactive. Therefore, consider the total BAU when determining the target maintenance dose for Northern Prairie grasses.
- Maintenance doses larger than 0.2 mL of undiluted allergen extract are rarely administered because an extract in 50% glycerin may cause patient discomfort upon injection.29
- After the maintenance dose is achieved, increase the injection interval to 2 weeks, then 3 weeks, and finally 4 weeks as tolerated. The optimal interval between maintenance doses of allergenic extract varies among individuals. Administer the maintenance dose at a given interval three or four times before further increasing the interval to ensure that no reactions occur. Protection may be lost rapidly if the interval between doses is more than 4 weeks.
Dosage Modification for Immunotherapy
Withhold immunotherapy and/or reduce dosage, if any of the following conditions exist:
- Severe symptoms of rhinitis and/or asthma.
- Infection accompanied by fever.
Any evidence of a systemic reaction is an indication for a significant reduction (at least 75%) in the subsequent dose. Repeated systemic adverse reactions are sufficient reason for the cessation of further attempts to increase the dose.
In situations prompting dose reduction, a cautious increase in dose can be attempted once the reduced dose is tolerated. The dose should be reduced to the last level not causing the reaction and maintained at this level for two or three treatments before cautiously increasing again.
Prolonged period has elapsed since the last injection: Patients may lose tolerance for allergen injections during prolonged intervals (> 4 weeks) between doses. The duration of tolerance is an individual characteristic and varies from patient to patient. In general, the longer the lapse in the injection schedule, the greater dose reduction required.
Changing to a different lot of standardized extract: All extracts can lose allergenic activity over time and extracts vary in allergenic activity. Two different lots of extract could differ substantially in allergenic activity, even if they are the same formula and concentration. The volume of the first dose from the new vial should not exceed 50% of the previous dose. Do not use extracts beyond their expiry date.
Changing to an extract from a different manufacturer: Since manufacturing processes and sources of raw materials differ among manufacturers, the interchangeability of extracts from different manufacturers cannot be assured. Decrease the starting dose of the new extract when the extract is the same formula and dilution as the one previously used. In general, a volume dose reduction to 50% of the previous product dose is adequate, but each situation must be evaluated separately considering the patient's history of sensitivity, tolerance of previous injections, and other factors. If the patient tolerates the 50% decrease, then raise the next dose to the previous tolerated dose amount. To re‑establish the maintenance dose the starting interval between doses should not be greater than one week.
Changes made in the extract concentrate formula: Changes other than those listed above such as a difference in extracting fluid (e.g., change from non-glycerin extracts to 50% glycerin extracts), combining two or more stock concentrates, or any other change can affect a patient’s tolerance of the treatment.23 Extra dilutions are recommended whenever starting a revised formula. The greater the change, the greater the number of dilutions required.
Duration of Treatment
The duration of treatment for immunotherapy has not been established. A period of three to five years of injection therapy constitutes an average minimum course of treatment. Evaluate patients for treatment response at least every 6 to 12 months while they receive immunotherapy. The decision to continue or stop immunotherapy must be individualized.23