Histamine Phosphate

INDICATIONS AND USAGE For use as a positive control in evaluation of allergenic (immediate hypersensitivity or "Type I") skin testing.

DOSAGE AND ADMINISTRATION Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit. For Prick, Puncture and Scratch Testing Histamine base 1 mg/mL (Histamine Phosphate 2.75 mg/mL) should be used to give a reaction. (Refer to Interpretation Section.) Prick, Puncture or Scratch Test Techniques The skin in the test area should be cleansed with alcohol and air dried. The histamine control skin test solution should be placed at the same site with the other skin test antigens, either on the patient's back or on the volar surface of the forearm. The patient should be placed in a comfortable position before the testing is begun. For the prick test, a sharp needle is used to puncture the skin, but not to draw blood. If the scratch test is used, carefully break or scratch the skin with a sterile scarifier. Do not draw blood. Each scratch should be about 2 mm - 4 mm in length. A small drop of the histamine base 1 mg/mL (Histamine Phosphate 2.75 mg/mL) is placed on the abraded skin site no closer than 4 or 5 cm from an adjacent test site. Some physicians prefer to place the solution on the test area and then prick through the drop with a sharp needle. Use a separate sterile scarifier or needle for each patient. The test should be read at 15 minutes; if a large wheal reaction occurs before that time the test site should be wiped free of histamine. Interpretation The patient's response is based on the size of: erythema (degree of redness) and/or size of wheal (smooth, slightly elevated area) which appear after 10 minutes. For percutaneous testing, different devices and/or techniques influence the size of the reaction. Therefore, it is important to refer to the device manufacturer's or distributor's instructions when grading reactions. For prick, puncture and scratch testing, histamine base 1 mg/mL (Histamine Phosphate 2.75 mg/mL) should be used to give a positive reaction. In a large population, the NHANES II survey reports a mean diameter (average of length and width) wheal of 4.4 mm ± 1.65 mm (± standard deviation) and a mean erythema of 18.4 mm ± 8.55 mm (± standard deviation) when using 25 gauge B-D needle by prick puncture (Pepys) technique. 7 All positive reactions should be interpreted against an appropriate negative control. For Intradermal Skin Testing Histamine base 0.1 mg/mL (Histamine Phosphate 0.275 mg/mL) or 0.01 mg/mL should be used to give a reaction. (Refer to Interpretation Section.) Intracutaneously (Intradermal) Test Techniques The skin should be cleansed with alcohol and air dried. A sterile one milliliter tuberculin syringe with 26 or 27 gauge needle should be used. A single sterile syringe should be used for each solution to assure sterility. Only the histamine base 0.1 mg/mL (Histamine Phosphate, 0.275 mg/mL) or greater dilution solution should be used. The histamine base skin test solution should be injected at the same site with the other skin test allergens, either on the patient's back or on the arm. The patient should be placed in a comfortable position before the testing is begun. The skin is held tense and the needle is inserted almost parallel to the skin, bevel side up, far enough to cover the beveled portion. Slowly inject 0.01 mL or 0.02 mL, making a small bleb approximately 3 mm - 5 mm in diameter. The test should be read in 15 minutes. Interpretation The patient's response is based on the size of: erythema (degree of redness) and/or size of wheal (smooth, slightly elevated area) which appear after 10 minutes. For intradermal skin testing, histamine base 0.1 mg/mL (Histamine Phosphate 0.275 mg/mL) or 0.01 mg/mL should be used to give a positive reaction. The available 0.1 mg/mL concentration must be diluted ten-fold to achieve this dose. All positive reactions should be interpreted against an appropriate negative control. In two successive years of testing, the Committee on Standardization of the American College of Allergy reported positive reactions at histamine base doses of 0.01 mg/mL and higher. Mean sum of wheal diameters was approximately 14 mm ± 4.8 mm and sum of erythema diameter was approximately 52 mm ± 21.6 mm following 0.01 mL intradermal doses of 0.01 mg/mL histamine base. When 0.01 mL of 0.1 mg/mL histamine base was injected, the sum of cross-diameters of wheal ranged from 15-20 mm and the sum of cross-diameters of erythema ranged from 60-80 mm. 8

ADVERSE REACTIONS Local: Reactions such as wheal, erythema and localized pruritus are to be expected, but if very large (i.e. greater than 4+ as described dosage and administration) may be the first manifestation of a systemic reaction. Systemic: Following the injection of large doses of histamine, systemic reactions may include flushing, dizziness, headache, bronchial constriction, urticaria, asthma, marked hypertension or hypotension, abdominal cramps, vomiting, metallic taste, and local or generalized allergic manifestations (see also OVERDOSAGE ).