Standardized Cat Hair Drug Information

• Diagnosis: Concentrated extract (10,000 BAU/mL) may be used for scratch or prick-puncture testing. Intradermal tests with serial three-fold dilution of the 10,000 BAU/mL showed the following results: Serial 3-Fold Dilutions of X The mean three-fold dilution eliciting a response of 50 mm sum of erythema diameters was 11.120 (S.D. 2,38). The number of BAU/mL required to elicit this response was 0.05 (range 0.0003 to 9.24 BAU/mL).
• This concentration is approximately a 1: 200,000 v/v dilution of the 10,000 BAU/mL extract.
• Extract for intradermal testing should be used as follows: Patients with a positive scratch or prick test to Standardized Cat Hair Extract. It is not advisable to perform an intradermal skin test in these patients. If the test is negative, a second test should be performed with 0.05 mL of a 1:200 v/v dilution of concentrate (50 BAU/mL). Patients tested only by the intradermal method with Standardized Cat Hair Extract. Patients suspected of being highly allergic to cats should be tested with 0.05 mL of a 1:200,000 v/v dilution (0.05 BAU/mL) of the concentrate.
• Interpretation Of Skin Tests: The interpretation of skin tests should be based on the size of the erythema and wheal response to the allergen compared to a negative saline control. A suggested method of scoring skin tests is shown below. Measurements refer to the longest (single), diameter of erythema and wheal response. Scratch and Prick Test A negative test shows only a slight red area at the site of scarification or prick penetration. The skin should be cleaned with 70% alcohol and aseptic technique should be observed in removing the extract from the vial. Care must be taken to avoid injecting the extract into a blood vessel because of the potential hazard of anaphylaxis. Standardized Cat Hair Extract must be diluted before administration to new patients. As a precaution against overdose, a skin test with the intended starting dose should be done to help evaluate the patient's sensitivity to the product. If the skin response is larger than 5/15 mm (edema/erythema), the extract should be diluted before it is given subcutaneously. The doses shown in the Dosage Schedule may be followed unless the patient's skin test response and allergic history indicate that more dilute extract should be used. Little is known about the required accumulated dosage of Fel d 1 (and other allergens that may be present in cat extract) that is needed to relieve symptoms. However, studies with other allergenic substances have shown that high dose immunotherapy is most efficacious in the treatment of allergic rhinitis and asthma. The amount of cat extract that is tolerated during immunotherapy depends upon the sensitivity of the patient. A burning sensation immediately following the injection of extract from the concentrate is due to the glycerol in the extract. It should not be interpreted as an adverse allergic response. Patients who have received allergenic extract for maintenance therapy SHOULD NOT be given the same dose from a fresh vial of extract. IT IS ADVISABLE TO REDUCE THE DOSAGE OF FRESH EXTRACT TO ONE-FOURTH THE AMOUNT GIVEN FROM A PREVIOUS LOT. Dosage Schedule for Standardized Cat Hair Extract (The safety and efficacy of this schedule has not been determined by well-controlled clinical trials.) v/v dilutions of concentrate containing 10,000 BAU per mL required to make the above concentrations.

Local Reactions From Skin Testing Large local reactions may result from skin tests with Standardized Cat Hair Extract. To help prevent this, a patient should be skin tested initially by the prick or scratch method. If a positive response is NOT observed, an intradermal skin test may be performed with a more dilute solution of the extract.

Oral antihistamines and topical corticosteroids may be administered to relieve itching and swelling resulting from large skin test reactions. Local Reactions From Subcutaneous Injections The occurrence of a hive 5 to 15 minutes after the subcutaneous injection of extract 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. However, 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 next injection administered should be 50% of the last nonreacting dose or less, depending upon the size and severity of the local reaction. Subsequent injections should be continued at the reduced dosage unless the physician responsible for treatment believes that it is safe to increase the dose, and that possible clinical improvement would result from the administration of a larger dose of extract.

Systemic Reactions Systemic reactions may range from a mild exacerbation of the patient's allergic symptoms to hives, anaphylactic shock, or even death from anaphylaxis. The reaction usually occurs 5 to 20 minutes after injection. As a rule, the more quickly a reaction develops, the more serious it is likely to become.

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 tracheotomy and for CARDIAC ARREST with cardiopulmonary resuscitation and other appropriate measures.

Standardized Cat Hair Extract should not be used for immunotherapy in persons who do not have cat related allergic symptoms and a positive skin test to the extract.

Placement of a tourniquet above the site of injection may be helpful in controlling the absorption of the extract. It should be released every 10 minutes and reapplied as needed. Intravenous antihistamines and hydrocortisone also may be used, but only after sufficient epinephrine has been given (See Adverse Reactions).