Repeated systemic reactions, however mild, are sufficient reason for the cessation of further attempts to increase the reaction-causing dose.
2.3.2 Maintenance Dose Selection, Adjustments, and Intervals
The maintenance dose is the dose that provides therapeutic efficacy without severe adverse local or systemic reactions. This dose may be limited by adverse reactions and may not be the original targeted maintenance dose. Select a maintenance dose based on the patient's clinical response and tolerance.
The following adjustments to the maintenance dose may be necessary.
Withhold immunotherapy and/or reduce dosage, if any of the following conditions exist:
In situations prompting dose reduction, a cautious increase in dosage can be attempted once the reduced dose is tolerated.
Decrease the interval between doses if symptoms develop before the next injection is scheduled.
In some patients, the dosage may be increased and/or the dosing interval shortened based on individual responses and dosing requirements. If the onset of symptoms is soon after the initiation of immunotherapy, decrease the interval between each dose.
Changing to a different lot of 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 a different formulation of extract or to an extract from a different manufacturer: 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.
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.
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. 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 two to three 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.