Pediatric Drug Allergy
Introduction
Introduction to pediatric drug allergy Drugallergy is one of the earliest observed allergic phenomena in humans. Historically, as humans searched for drugs to treat diseases, they have successively produced drug poisoning and allergies. According to legend, Shennong, the ancestor of ancient Chinese pharmacology, In the past 3,000 years before BC, he had encountered seventy poisons in one day because of the taste of herbs. From the point of view of modern medicine, there may be drug allergies in this seventy poisons. With the increasing enrichment of human material life, the development of medical and health care, people have more opportunities to receive medical treatment, and the problem of drug allergy is also increasing. See important. At present, drug allergy has become a problem that has received widespread attention in the clinical community. basic knowledge The proportion of illness: 2.2% Susceptible people: children Mode of infection: non-infectious Complications: Asthma, anaphylactic shock, hemolytic anemia, vasculitis
Cause
Pediatric drug allergic etiology
Environmental factors (35%):
The way the drug enters the body is very important in inducing allergic reactions. Local skin treatment is more sensitive than other routes, and oral sensitization is rarely used. For example, ethylenediamine is often used as a matrix for stabilizers and antihistamines, in aminophylline. It is also contained, and after local sensitization with ethylenediamine, oral or intravenous aminophylline can cause systemic dermatitis.
Drug factors (25%):
The more frequently the drug treatment frequency is treated, the longer the treatment lasts, and the greater the risk of allergic reactions. Intermittent treatment is more susceptible to sensitization than continuous treatment.
Other factors (15%):
The use of immunosuppressive agents.
Common sensitizing drugs are penicillin, aspirin or non-steroidal anti-inflammatory agents and allergen extracts.
Pathogenesis
1. IgE-mediated allergy: this type can be expressed as urticaria / angioedema, allergic rhinitis / asthma, severe airway obstruction, shock, coma, and even death, this type is not serious in children .
2. Cytotoxic reaction: Because the drug directly reacts with the tissue, it is easy to cause tissue damage, such as immunological hemolytic anemia caused by penicillin, quinine, quinidine, analgin, etc., which is the antibody against red blood cells.
3. Immune complex reaction: Serum disease is a systemic immune response, forming a soluble antigen-antibody complex that activates complement to cause tissue damage, clinical manifestations of fever, urticaria, lymphadenopathy and arthritis, occasional peripheral neuritis , vasculitis and glomerulonephritis, primary serum disease is rare in children.
4. Cell-mediated hypersensitivity: This type may be more common in drug reactions, including topical antihistamines, benzocaine, ethylenediamine, corticosteroids, neomycin, and p-aminobenzoic acid. Causes allergic contact dermatitis, oral sulfonamides and other drugs are prone to fixed drug eruptions, it is particularly important that the preparation for skin is susceptible to sensitization.
Prevention
Pediatric drug allergy prevention
The prevention of drug allergy is to find out the specific sensitizing drugs of patients, and strictly avoid them. In the case that sensitizing drugs are not clear, the measures to prevent drug allergies can be summarized as the following points.
1. Raise the ideological alert for drug allergy
All clinical staff should always be alert to the occurrence of drug allergies. Before using the drug, you should ask whether there has been a history of allergies in the past, a history of family allergies, and especially whether you have a history of drug allergy in the past and a history of allergies to which drugs. For patients suspected of having a drug allergy episode, the current and recent medication should be asked in detail, and if necessary, the patient should be tested for drug specificity.
2. Strictly consider the indications for medication
For some drugs that are allergic to allergies, it should be strictly controlled. If there is no clear indication, try to use it as little as possible or use it. According to Rosenthol, the results of post-mortem investigations on 30 patients with anaphylactic shock caused by penicillin have found that 30 Only 12 of the people had clear indications for penicillin, and the other 18 cases were not absolutely necessary for penicillin. This indicates that many patients with severe drug allergies have defects in the drug use, which is worth noting.
3. Strict drug allergy
The history of medical records recorded that some of the drug allergies are due to omissions recorded in the medical history, so it should be emphasized that those who have a history of drug allergies must be marked on the front page of the medical record, with a red pen to indicate the warning, so that the patient is At the time of the visit, the doctor's drug allergy to the patient is clear at a glance, and should be used as a system to implement together.
4. Avoid repeated intermittent medication
Allergies to drugs are often formed in repeated intermittent medications. Doctors, nurses, and drug workers suffer from more drug allergies than normal people, which may indicate that repeated intermittent drug exposures may cause allergies.
5. Adopt safe drug route
In drug allergies, severe allergies are mostly caused by drug injection. In various injection methods, intravenous and intramuscular injections cause the fastest and most severe allergies. Subcutaneous injections and drug inhalation are followed by oral and topical drugs. Less, so when considering the patient's medication route, it should be safe to use as much as possible. Anyone who can take an oral replacement instead of injection should be exempted from injection to prevent serious drug allergy.
6. Use less drug that causes allergies
Different drugs have different opportunities for allergies. Some of them are more susceptible to allergies. Some drugs are relatively less allergic, and some drugs do not cause allergies at all. This issue has been discussed above, so when choosing drugs in the clinic, To prevent drug allergies, it is advisable to use less drugs that cause allergies. As far as our preliminary investigation is concerned, Chinese medicines cause less allergies than Western medicines, and acupuncture can completely avoid drug allergies. This is a favorable condition for clinical talents in China. Should try to play its role, in the case of drug allergies, consider using traditional Chinese medicine and acupuncture to replace allergic drugs. In recent years, patients who are allergic to some anesthetics have used acupuncture anesthesia to successfully complete the operation, which is indeed allergic to anesthetics. The gospel of the patient.
7. Use the necessary anti-allergic measures
All clinical units, including outpatient clinics, wards, operating rooms, treatment rooms, injection rooms, etc., should be equipped with all necessary drugs and other equipment to prevent drug allergies, including adrenaline injections, isoproterenol aerosols. , tourniquet, oxygen, etc. Just in case, adrenaline is used for the rescue of allergic shock. Isoproterenol aerosol is used for asthma and airway obstruction caused by drug allergy, such as serious illness caused by injection of drugs by the limb. In case of allergies, the limbs are tied with a tourniquet at the proximal end of the injection area to slow the absorption of the drug, and oxygen is used for first aid in the case of an allergic shock or an asthmatic hypoxia.
8. Strengthen observation after medication
Many serious drug allergies occur within a few minutes to 15 minutes after drug injection. Therefore, if the patient is used in a hospital outpatient or injection room, it is best to leave the patient in the office for 10 to 15 minutes. If there is no adverse reaction, then leave it. The patient was allergic to the midway after leaving the hospital, which made the treatment difficult.
Complication
Pediatric drug allergy complications Complications asthma anaphylactic shock hemolytic anemia vasculitis
Severe cases of exfoliative dermatitis, toxic epidermal necrolysis, asthma, anaphylactic shock, systemic lupus erythematosus-like reactions, hemolytic anemia and vasculitis.
Symptom
Pediatric drug allergy symptoms Common symptoms Drug allergic reaction maculopapular edema nodule fever exfoliative dermatitis shock
1. Skin symptoms: The rash is the most common, and the drug can cause a variety of allergic skin rashes, including urticaria/angioedema, maculopapular rash, measles-like rash, erythema multiforme, allergic purpura, nodular erythema and fixed drug eruption. In addition, it can be itchy and rash-free, the most serious cases are exfoliative dermatitis, bullous rash, severe bullous polymorphic erythema and toxic epidermal necrolysis, allergic purpura is more common in children, occasionally salicylic acid Caused by salt, children with nodular erythema are rare.
2. Drug fever: It can be the only manifestation of adverse drug reactions. It can also occur before other symptoms or coexist with other symptoms. The incidence of drug fever in children is low. Aspirin, penicillin and other antibiotics are common in children. .
3. Immediate hypersensitivity reactions: such as allergic eye rhinitis / asthma, anaphylactic shock, etc.
4. Others: hepatitis, allergic pneumonia, kidney disease, systemic lupus erythematosus-like reactions, hemolytic anemia and vasculitis.
Examine
Pediatric drug allergy test
1. General inspection
Blood, urine, routine examination, can be found in peripheral blood eosinophils increased.
2. Specific test
Specific tests for serum antibody tests and drug allergies are designed to determine which drugs are sensitized to patients, which is a key issue in drug allergy control.
(1) Drug allergy specific test
However, there are many methods for the specific diagnosis of drug allergy, but the correct rate is not high, false positives and false negatives are present at all times. The accuracy of drug-specific skin tests is only about 50%. Some people even report that only 25 %, as far as the results of our clinical trials for a large number of patients with drug allergy, the coincidence rate between their medical history and skin test results is less than 50%.
(2) Method
At present, there are 8 kinds of specific test methods for drug allergy: 1 patch method; 2 scratch method; 3 point thorn method; 4 conjunctival method; 5 tongue containing method; 6 intradermal method; 7 skin window method; Drug challenge test, which is more commonly used by patch method, scratch method, puncture method and intradermal method. The accuracy is the highest in intradermal method, but the intradermal test can only be used for some skin non-irritating. Injectable solutions, such as penicillin, streptomycin, etc., other dosage forms are not applicable, and for those who are allergic to certain high-drugs, there are people who have severe shock response caused by intradermal test, so care should be taken during use. After adequate dilution, the dose should be strictly controlled to prevent the occurrence of severe allergies.
The use of drug allergy challenge test should be cautious. For those who have severe allergic reactions, it is forbidden to use it to prevent accidents. Generally, people who use oral drugs cause gastrointestinal or skin reactions; after skin test, no clear results can be obtained. When the patient's allergy symptoms disappeared, after stopping all the drugs, the unit dose of the suspected sensitizing drug was orally administered, and the gastrointestinal or skin allergic reaction was observed for 24 to 48 hours.
(3) False negative
The specificity test of drug allergy has certain limitations, and it is prone to false negative or false positive reaction. The reasons for false negative results are as follows: 1 Allergic shock tissue is not in the skin tissue of the test site. 2 The skin of the test skin has limited absorbability to the test drug. 3 Most of the drugs used for the test are incomplete antigens, which must be combined with plasma proteins to be antigenic. 4 When patients are taking antihistamines, ephedrine, adrenaline, corticosteroids, etc., they can affect skin reactivity.
(4) False positive
The reasons for the false positive results are as follows: 1 The drug itself has non-specific irritant, such as acid, alkaline, expectorant, ether and other drugs have certain irritation to the skin. 2 physical non-specific stimuli of the test itself, such as scratches, pricks, injections, skin window, etc., can cause certain non-specific reactions in the skin. 3 impurities, dyes, excipients, flavors, etc. in the drug may also cause allergies, which is confused with the drug itself. 4 A small amount of air is injected during the intradermal test, and a false positive reaction may occur.
In summary, the specific test of drug allergy has many defects, and there are certain restrictions on the final diagnosis of sensitizing drugs; but it still plays a big role in preventing serious drug allergy. In China, since Penicillin, streptomycin has been widely used in the prevention of severe penicillin and streptomycin allergic reactions since it was widely used in routine skin tests before injection. Even though it still has many shortcomings, it is practical for drug allergy-specific skin tests. The meaning is undeniable.
(5) The significance of the drug allergy specific test is
1Reference meaning: It is important for the specific diagnosis of drug allergy. Although the negative result can not completely rule out the possibility of allergy, the positive result is very helpful for determining allergy drugs.
2 Establish diagnosis: If a partial skin test occurs and the symptoms of the body are consistent with the symptoms of the drug allergy, it is of great significance for establishing a specific diagnosis.
3 to help diagnose: for contact dermatitis caused by drug allergies, skin patch test can often lead to local skin symptoms similar to the onset of the disease, which is of great significance for the diagnosis.
3. Radiological diagnosis
Including chest fluoroscopy, radiography, bronchography, sinus radiography, gastrointestinal angiography, etc., also have important diagnostic significance for some allergic diseases, especially for the diagnosis of allergic pneumonia, allergic sinusitis, X-ray examination Special important value. In addition, X-ray examination can help identify other non-allergic diseases and eliminate complications. Modern imaging diagnosis includes: B-ultrasound, CT, magnetic resonance, etc., and if necessary, for the auxiliary diagnosis of allergic diseases. .
4. Pharmacy diagnosis
For some allergic diseases, certain drugs that are effective for allergies, such as adrenaline, 2 receptor agonists, various antihistamines, may also be used in cases where various tests cannot be confirmed. Adrenal corticosteroids, etc., for exploratory treatment, if the efficacy of the drug is excellent, the diagnosis of allergic disease can be cited from the side, but in the diagnosis of this tentative drug, the condition must be fully considered, and the drug to be tested should be excluded. Contraindications to patients and possible side effects.
Diagnosis
Diagnosis and diagnosis of pediatric drug allergy
diagnosis
1. History Before making a correct diagnosis, you should know in detail the history of the adverse reactions before and at the beginning, first of all to determine whether the drug is caused by the original infection.
2. The rapid skin test is helpful in diagnosing IgE-mediated hypersensitivity reactions, such as penicillin and insulin allergy. Children who are highly sensitive to penicillin should complete a safe rapid patch test.
3. The patch test is suitable for patients with contact dermatitis caused by any drug.
4. Laboratory diagnosis Because of the different mechanisms of various allergic reactions, there is no single test method for drug allergic reactions.
5. Inflammatory test drug challenge test is only suitable for patients who cannot be diagnosed according to the skin test and who are allergic to drugs. For example, if they are sensitive to aspirin and apply to local anesthetics, they should be used with great care and should not be used for height. Sensitive children.
Differential diagnosis
Whether the rash is allergic or non-allergic can be analyzed according to the following criteria.
1. Previous tolerance to drugs: Patients have been well tolerated in the past for drugs that cause allergic reactions.
2. Drug dosage: The occurrence of drug allergy occurs mostly in the usual therapeutic doses, sometimes less than the usual doses, so the toxicity or accumulation can be excluded accordingly.
3. Clinical manifestations: The manifestations of drug allergy, often similar to allergic diseases caused by other substances, but different from the pharmacological effects of drugs. For abnormalities in treatment, when clinical features such as serum-like reactions, anaphylactic shock, urticaria, angioedema, asthma, and contact dermatitis are associated with typical allergic diseases, drug allergies should be considered. The possibility.
4. Latency: The occurrence of allergic reaction, with a positive incubation period, usually 7 to 10 days. When it is shorter than the incubation period, it does not react to the drug used because the allergic state has not yet formed. After the allergic state is formed, the drug will be used for a period of tens of minutes to 24 hours, usually no more than 72 hours.
5. Recurrence of the reaction: Once the reaction occurs, the drug or a drug having a similar chemical structure can be used later, which is used in a small amount and can cause recurrence.
6. Occurs in susceptible individuals: this reaction is only seen in a few people with susceptibility. Such people or members of their families often have a history of allergic diseases. Be careful not to treat other drug reactions as drug allergies.
7. Self-limiting of the course of the disease: The vast majority of the course of the disease is self-limiting, and can be quickly resolved after the sensitization of the drug is stopped, with a few exceptions.
8. Others: Antihistamines and corticosteroids have a good effect; some patients have increased eosinophils. These can help to judge, but it should be noted that some other diseases can also be similar, so it can only be used as a reference. Identification of the disease.
