Histamine

INDICATIONS AND USAGE Positive Skin Test Control - Histamine is indicated as an adjunct in allergy skin test for diagnosis, as a positive control to test wheal-flare response of skin for evaluation of skin test response to allergenic extracts.

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

WARNINGS Care must be taken in intracutaneous testing to avoid injection into a venule or capillary. Pull back gently on the syringe plunger and note if blood is drawn. If blood is drawn, withdraw needle and inject into another skin site. Small doses by any route of administration may precipitate asthma in patients with bronchial hyperactivity. This product is not intended for inhalation, or subcutaneous injection. The utmost caution is advised in using histamine in such patients and in those with a history of bronchial asthma.

CONTRAINDICATIONS Histamine should not be injected into individuals with hypotension, severe hypertension, severe cardiac, pulmonary, or renal disease. Not to be used for diagnosis of pheochromocytoma or to test the ability of the gastric mucosa to secrete hydrochloric acid.

Drug Interactions Drugs can interfere with the performance of skin tests in general, and specifically with histamine 1 . Antihistamines: Response to histamine is suppressed by antihistamines. The length of suppression varies, and is dependent on individual patient, type of antihistamine and length of time the patient has been on antihistamines. The duration of this suppression may be as little as 24 hours (chlorpheniramine), and can be as long as 40 days (astemizole). Tricyclic Antidepressants: These exert a potent and sustained decrease of skin reactivity to histamine, which may last for a few weeks. Beta 2 Agonists: Oral terbutaline and parenteral ephedrine, in general, have been shown to decrease allergen induced wheal. Theoretically, this may also reduce whealing capacity to histamine. Dopamine: Intravenous infusion of dopamine has been shown to inhibit skin test responses to histamine. Beta Blocking Agents: Propranolol can significantly increase skin test reactivity, including histamine. Other Drugs: Short acting steroids, inhaled beta agonists, theophylline and cromolyn do not seem to affect skin test response.

ADVERSE REACTIONS Large doses of histamine may precipitate systemic reactions. These reactions may include flushing, dizziness, headache, bronchial constriction, urticaria, asthma, marked hypotension or hypertension, abdominal cramps, vomiting, metallic taste, local or generalized allergic manifestations. An antihistamine preparation may be given orally, I.M. or I.V. to prevent or ameliorate systemic reactions to the drug. If a systemic or anaphylactic reaction does occur, apply a tourniquet above the site of injection and inject 1:1000 epinephrine-hydrochloride intramuscularly or subcutaneously into the opposite arm. Loosen the tourniquet at least every 10 minutes. Do not obstruct arterial blood flow with the tourniquet. Epinephrine Dosage: ADULT: 0.3 to 0.5 mL should be injected. Repeat in 5 to 10 minutes if necessary. PEDIATRIC: The usual initial dose is 0.01 mg (mL) per kg body weight or 0.3 mg(mL) per square meter of body surface area. Suggested dosage for infants to 2 years of age is 0.05 mL to 0.1 mL; for children 2 to 6 years, 0.15 mL; and children 6 to 12 years, 0.2 mL. Single pediatric doses should not exceed 0.3 mg (mL). Doses may be repeated as frequently as every 20 minutes, depending on the severity of the condition and the response of the patient. After administration of epinephrine, profound shock or vasomotor collapse should be treated with intravenous fluids, and possibly vasoactive drugs. Oxygen should be given by mask. Aminophylline or adrenal corticosteroids may be used if necessary after adequate epinephrine and circulatory support has been given. Emergency resuscitation measures and personnel trained in their use should be available immediately in the event of a serious systemic or anaphylactic reaction not responsive to the above measures (Ref. J. ALLERGY AND CLINICAL IMMUNOLOGY 77s (2): p. 271-273, 1986). 16 Rarely are all of the above measures necessary, the tourniquet and epinephrine usually producing prompt responses. However, the physician should be prepared in advance for all contingencies. Promptness in beginning emergency treatment measures is of utmost importance. Adverse Event Reporting Report all adverse events to Jubilant HollisterStier LLC Customer Technical Services Department at 1 (800) 992-1120. A voluntary adverse event reporting system for health professionals is available through the FDA MEDWATCH program. Preprinted forms (FDA Form 3500) are available from the FDA by calling 1 (800) FDA-1088. Completed forms should be mailed to MEDWATCH, 5600 Fisher Lane, Rockville, MD 20852-9787 or Fax to: 1 (800) FDA-0178.

CLINICAL PHARMACOLOGY Pharmacological actions of histamine include the increase of capillary and post capillary venular permeability. This vascular change leads to the wheal-flare response. Large reactions can cause an amplification of a reaction to a nearby skin test. Histamine is degraded either by oxidative deamination or by methylation and oxidative deamination so that the principal excretion products are imidazoleacetic acid-riboside and 1-methyl imidazoleacetic acid respectively. 2 10 atopic subjects and 10 non-atopics were tested with Positive Skin Test Control - Histamine Solutions, and two negative control solutions. Thirteen females (35-49 years old; mean age 36.5) and 7 males (23-45 years old; mean age 36.4) were tested. This study included 19 Caucasian subjects and 1 African American subject. Different skin test devices produce different skin test responses. (14,15) Study results are summarized in Table 1 and Table 2. Atopic and non-atopic subject information was combined, as there were no significant differences in their skin responses. Summation of wheal (∑W) or summation of erythema (∑E) was determined by measuring the longest diameter and the mid-point orthoganol diameter of the wheal or erythema response and summing the two measurements. Malling tested 25 subjects using a straight needle prick technique with Histamine Dihydrochloride 10mg/mL and found wheal single diameters of 5.4-8.5mm (mean 7 mm). 13 Histamine Dihydrochloride at 10mg/mL has been shown to elicit fewer false negative and false positive reactions than Histamine Dihydrochloride at 1mg/mL. 12 10mg/mL Histamine Dihydrochloride has been shown to be the appropriate strength to perform biological standardization using skin reactivity to histamine as a standard of comparison. 11,13 Histamine Table1 Histamine Table2