Cat Hair Standardized

GENERAL

The dosage should be reduced 50-75% from the previous dose when starting a patient on a new lot of standardized cat hair extract from the same manufacturer or from a different manufacturer. When changing from a non-standardized cat hair extract to a standardized cat hair extract, the dose should be based upon comparative skin testing or the patient should be treated as though beginning treatment for the first time.

A separate sterile tuberculin type syringe should be used with each patient to prevent cross contamination of extracts. This will also prevent transmission of disease such as serum hepatitis, AIDS and other infectious diseases. Aseptic technique should always be used when injections of allergenic extracts are administered.

CARCINOGENESIS, MUTAGENESIS, IMPAIRMENT OF FERTILITY:

Long term studies with extracts have not been conducted in animals to determine their potential for carcinogenesis, mutagenesis, or impairment of fertility.

PREGNANCY:

Pregnancy Category C.

Animal reproduction studies have not been conducted with allergenic extracts. It is also not known whether allergenic extracts can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity. Allergenic extracts should be given to a pregnant woman only if clearly needed.

Controlled studies of hyposensitization with moderate to high doses of allergenic extracts in pregnant women have failed to demonstrate any risk to the mother or fetus. (6)

However, with histamines known ability to contract uterine muscles any reaction which would release significant amounts of histamine such as hyposensitization overdose should be avoided. The physician must weigh the benefits of immunotherapy against the risk of anaphylactic reactions that could result in harm to the mother and/or fetus.

Hyposensitization should be used during pregnancy only if clearly necessary and administered cautiously. If a woman is on maintenance dose the occurrence of pregnancy is not an indication to stop injection therapy.

NURSING MOTHERS:

It is not known if allergenic extracts are excreted in human milk therefore caution should be exercised when extracts are administered in nursing women.

PEDIATRIC USE:

Doses of allergenic extracts for children are generally the same as those for adults. The extracts may cause some pain or discomfort when injected. The maximum tolerated dose may be less than the adult dose due to the smaller size of the child. Therefore, the volume of the dose may need to be adjusted from the adult schedules provided.

DRUG INTERACTIONS:

Patients who are taking non-selective beta blockers may be more reactive to allergens given for testing or treatment and may be unresponsive to the usual doses of epinephrine used to treat allergic reactions. Antihistamines can significantly inhibit the immediate skin test reactions. Patients should be free of such medication for at least 48 hours before testing.

Local reactions:

Some swelling and redness at the site of injection is not unusual. Mild burning that occurs immediately after the injection is normal; this usually subsides in 10 to 20 seconds. If the swelling and redness persist for a period of 24 hours or longer this should be a sign to proceed with caution in increasing the dosage. With the next injection the dosage should remain the same or be decreased. Large local reactions may indicate that a systemic reaction could occur with the next injection if the dosage was increased. If a patient continues to have reactions at the maintenance dose, the patient is considered to have exceeded the maximum tolerated dosage.

Systemic Reactions:

Systemic reactions occur infrequently but must be looked for in all patients, especially highly sensitive patients. Anaphylactic shock and death are always possible. Therefore, physicians must be prepared for the treatment of these reactions. Systemic reactions can also be characterized by one or more of the following symptoms: angioedema, tachycardia, conjunctivitis, cough, fainting, hypotension, pallor, rhinitis, urticaria, and wheezing.

Systemic reaction can be treated by the immediate application of a tourniquet above the site of injection and the administration of 0.3 to 0.5ml of 1:1000 Epinephrine - Hydrochloride subcutaneously or intramuscularly at the site of allergen injection. The dosage may be repeated two times at 15 minute intervals. Loosen the tourniquet at least every 10 minutes.

The pediatric dosage for 1:1000 Epinephrine-Hydrochloride is 0.05 to 0.1ml for infants to 2 years of age; 0.15ml, for children 2 to 6 years; and 0.2ml, for children 6 to 12 years.

Patients should always be observed for at least 30 minutes after any injection. Hypotension can be reversed by using vasopressor agents and volume expanders. Parenteral aminophylline and inhalation bronchodilators may be required for bronchospasm. Oxygen may also be needed. Maintenance of an open airway is critical if upper airway obstruction is present. Adrenal corticosteroids and intravenous antihistamine can be given after adequate epinephrine and circulatory support has been administered. Physicians must be familiar with these systemic reactions and have all the equipment and drugs necessary for proper treatment. (7)

The number of skin tests applied at one time will depend on the particular patient and their allergic history. These tests should be performed and observed in 15 to 20 minutes. Additional tests may be applied in sequence. Perform tests on the anterolateral aspect of the upper arm on an area that permits the effective application of a tourniquet proximal to the site of the test. The skin at the site of injection should be disinfected with rubbing alcohol before testing.

Puncture testing: Apply one drop (0.05ml) of extract to the skin. Pierce the drop of extract and skin using a sterile hypodermic needle or vaccinating needle. Maintain the needle perpendicular to the skin surface and rock the needle back and forth to produce a small hole without bleeding. Do not rotate or gouge the needle. Remove needle from skin and wipe excess extract from skin surface.

Scratch testing: Using a scarifier or needle, make a scratch 1/16 inch long on the epidermis penetrating the outer cornified area but being careful not to draw blood. Apply one drop (0.05ml) of allergen to the scratch.

Intradermal testing: Use a separate sterile syringe (tuberculin type equipped with a 27 gauge by 3/8 inch needle with intradermal bevel) for each antigen. The tests are made by injecting 0.02ml of allergen into the epidermis. If the test has been performed properly, the solution should raise a bleb 2 to 3mm in diameter.  If the bleb does not appear, the injection was made too deeply.

A negative control consisting of the same solution that the extract was prepared in should be applied to one of the sites in the same manner as the tests being performed. For example, the negative intradermal control should contain 0.5% (v/v) glycerin, if a 100 BAU/ml concentration cat hair is used for intradermal testing. Histamine phosphate should be used as a positive control for evaluation of skin testing. Histamine phosphate is available from other manufacturers. See their directions for use, for recommended dosage and interpretation of results. 

A positive reaction usually develops in 15-20 minutes. The positive response is a wheal and flare reaction that is larger than the negative control and judged on the size of the reaction. Scratch or puncture tests may not elicit as large and well defined reaction as the intradermal. (5)

The following system is recommended (8):

The following are two methods of injection therapy:

1. Pre-seasonal in which treatment is begun three months before seasonal difficulty begins and brought to maintenance dose by injections four to seven days apart and discontinued after that season ends.
   
2. Perennial treatment is the recommended mode of therapy in which the patient is, by injection therapy, brought up to tolerated maintenance dose and remains at that dose until amelioration of allergic symptoms occurs. Injections may be given at intervals of 4 to 7 days.

Allergenic extracts must be diluted before use. Normally immunotherapy can be started with a 1 BAU/ml dilution. If a patient appears to be extremely sensitive, dilutions of the antigen can further be made before injections are started. The following are suggested procedures for making a proper dilution series. Recommended diluents contain 0.9% sodium chloride and 0.4% phenol as a preservative.

Perennial treatment may be started using the following dosage and dilution schedule. THIS SCHEDULE IS ONLY ILLUSTRATIVE AND HAS NOT BEEN SUBJECTED TO ADEQUATE OR WELL-CONTROLLED TRIALS TO DETERMINE EITHER ITS SAFETY OR EFFICACY.

Gradually increase the dose as outlined in the schedule. If you give a dose that causes a mild local reaction manifested by warmth or redness, repeat the same dose. If the reaction is severe or systemic (manifested as hives, asthma, or hay fever), drop back a dose in schedule and build again. If a severe local reaction or a systemic reaction is again encountered, this should be considered more than the maximum tolerance for this patient. The maintenance dose is the largest dose that relieves symptoms without producing local reactions. The size and interval of doses will vary and can be adjusted as necessary. The normal interval between doses is 4 to 7 days.

Bulk extract (stock concentrate) in 50% (v/v) glycerin containing 10,000 BAU/ml is supplied in 10ml, 30ml, and 50ml vials. Scratch testing in 50% (v/v) glycerin containing 10,000 BAU/ml is supplied in 2ml dropper vials. Intradermal testing (aqueous) containing 100 BAU/ml is supplied in 5ml vials.

These extracts should be stored at 2 to 8 degrees Celsius. Excessive heating (above room temperature) and repeated freeze-thawing should be avoided. The dating period (expiration date) is shown on the vial label. Once extracts are diluted the shelf life decreases. Extracts should be re-ordered when out of date. Please allow a minimum of three (3) weeks for delivery due to the holding period for sterility testing.