Diagnostic – Penicillin Allergy
Action And Clinical Pharmacology: The major antigenic determinant of penicillin hypersensitivity is the penicilloyl group, a degradation product of penicillin. Pre-Pen reacts specifically with penicilloyl skin sensitizing antibodies (reagins) to produce immediate wheal and flare reactions which may reflect increased risk of allergic reactions to subsequent penicillin therapy.
Indications And Clinical Uses: As a skin test reagent for the detection of penicilloyl reagins. Use is indicated whenever there is a need to determine the presence or absence of these reagins. Prospective skin testing in patients with known or possible histories of penicillin intolerance may be useful for assessing the allergic status. Retrospective skin testing may also be useful in determining if a prior drug reaction may have been due to penicillin exposure. Pre-Pen skin testing may be useful in patients undergoing allergy evaluations where exposure to penicillin in the environment may be a factor.
Contra-Indications: Skin testing for detection of reagin with specific haptenes is never without risk. Skin testing patients known to be extremely hypersensitive to penicillin should not be done unless there is a very strong medical reason for administering penicillin.
Manufacturers’ Warnings In Clinical States: There are insufficient data to assess the potential danger of sensitization to repeated skin testing with Pre-Pen. Rarely, a systemic allergic reaction may follow a skin test with Pre-Pen. This can be avoided by making the first application by scratch test and very carefully following the instructions in administering the intradermal test, using the intradermal route only if the scratch test has been entirely negative. Skin testing with penicillin and/or other penicillin-derived reagents should not be performed simultaneously.
Precautions: There are insufficient data derived from well-controlled studies to determine the value of the Pre-Pen skin test as a means of assessing the risk of administering therapeutic penicillin in the following situations: adult patients who give no history of clinical penicillin hypersensitivity; pediatric patients.
In addition, there are no data at present to assess the clinical value of Pre-Pen where exposure to penicillin is suspected as a cause of a drug reaction and in patients who are undergoing routine allergy evaluation.
Furthermore, there are no data relating the clinical value of Pre-Pen skin tests to the risk of administering semi-synthetic penicillins and cephalosporin-derived antibiotics.
Recognition that the following clinical outcomes are possible makes it imperative for the physician to weigh risk to benefit in every instance where the decision to administer or not to administer penicillin is based in part on a Pre-Pen skin test: an allergic reaction to therapeutic penicillin may occur in a patient with a negative skin test to Pre-Pen; it is possible for a patient to have an anaphylactic reaction to therapeutic penicillin in the presence of a negative Pre-Pen skin test and a negative history of clinical penicillin hypersensitivity; if penicillin is the absolute drug of choice in a life-threatening situation, successful desensitization with therapeutic penicillin may be possible irrespective of a positive skin test and/or a positive history of clinical penicillin hypersensitivity.
Pregnancy: Animal reproduction studies have not been conducted with Pre-Pen. It is not known whether it can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity. The hazards of skin testing in such patients should be weighed against the hazards of penicillin therapy without skin testing.
Adverse Reactions: Urticaria, generalized pruritus, local swelling, generalized flushing, anaphylaxis, bronchospasm, fainting and maculopapular eruption. The overall incidence of such reactions appears to be less than 1 in 1 000. There is indication, however, that the incidence is higher in patients with a history of penicillin intolerance.
Dosage And Administration: Skin testing is usually performed on the inner volar surface of the forearm. The skin test material may be applied by the scratch technique or by intradermal injection. (It is particularly desirable to start with a scratch test.) If the scratch test produces a positive reaction, it is not necessary or desirable to do the intradermal test. If no reaction occurs to the scratch test within 5 minutes, the intradermal test should be performed. There is sufficient material in the ampul to perform both tests.
Using a tuberculin syringe with a 26 gauge needle, withdraw the contents of the ampul. A drop is sufficient for the scratch test. At the appearance of a wheal and/or flare, the excess material should be wiped off to avoid a possible severe systemic reaction.
The intradermal test is performed by injecting not more than 0.03 mL of the material intradermally. It is important not to increase the volume of the injection, since tissue reaction to larger volumes can be confused and misinterpreted as weakly positive tests. Many allergists recommend injecting only enough material to make the smallest discernible bleb. Detection of skin response is facilitated if the size of the initial bleb is outlined on the skin with a fine-line ballpoint pen. Most skin reactions develop within 5 minutes, but patients who do not respond to the test should be observed for up to 20 minutes. Responses to Pre-Pen are graded as follows: (-) negative response: no increase in size of original bleb; (±) ambiguous response: wheal being only slightly larger than initial injection bleb, with or without accompanying erythematous flare; (+) positive response: marked increase in size of original bleb. Wheal may exceed 20 mm in diameter and exhibit pseudopodia.
It is desirable also to include a saline control to rule out skin reactions due to dermographia.
Availability And Storage: Each single dose ampul contains: a sterile solution of benzylpenicilloyl-polylysine 0.20 mL in a concentration of 6.0´105M (penicilloyl) in phosphate buffer 0.01 M and sodium chloride 0.15 M. Packages of 5.
Store in the refrigerator. Test materials subjected to ambient temperatures for over a day should be discarded.
PRE-PEN® Rivex Pharma Benzylpenicilloyl-Polylysine Diagnostic – Penicillin Allergy