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Dermatology and Venereology 006 Drug Rash
In dermatology and venereology, drug eruption is an inflammatory reaction of the skin and mucous membranes caused by drugs entering the human body through oral administration, injection, inhalation, suppository, infusion, external drug absorption, etc.; it is a manifestation of adverse drug reactions and the most common type.
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Dermatology and Venereology 006 Drug Rash
- One Hundred Years of Solitude Character Relationship Chart
One Hundred Years of Solitude is the masterpiece of Gabriel Garcia Marquez. Reading this book begins with making sense of the characters' relationships, which are centered on the Buendía family and tells the story of the family's prosperity and decline, internal relationships and political struggles, self-mixing and rebirth over the course of a hundred years.
- One Hundred Years of Solitude Character Relationship Chart
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Project management is the process of applying specialized knowledge, skills, tools, and methods to project activities so that the project can achieve or exceed the set needs and expectations within the constraints of limited resources. This diagram provides a comprehensive overview of the 8 components of the project management process and can be used as a generic template for direct application.
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- Outline
Chapter 6 Drug Rash
drug rash
【Definition】drug eruption/dermatitis medicamentosa
It is an inflammatory reaction in the skin and mucous membranes caused by drugs entering the human body through oral administration, injection, inhalation, suppositories, perfusion, external drug absorption, etc. It is a manifestation of adverse drug reactions and the most common type.
【Cause】
individual factors
Influence of genetic factors (allergic constitution), certain enzyme defects, and pathological/physiological conditions of the body
drug factors
Antibiotics: penicillins, cephalosporins, tetracyclines, aminoglycosides
Sulfonamides: Sulfamethoxazole
Antipyretic and analgesic: salicylic acid preparations
Anti-epileptic and sedative drugs: phenytoin, barbiturates, Chinese herbal medicines
Others: allopurinol, isoniazid, furazolidone, hydralazine, allogeneic serum preparations/vaccines, biological agents
【Pathogenesis】
allergy
type
Type I allergic reaction (anaphylaxis/immediate allergic reaction): more common in penicillin allergy; manifested as urticarial drug eruption, angioedema, and anaphylactic shock
Type II allergic reaction (cytotoxic allergic reaction): such as erythema multiforme type drug eruption; often accompanied by cytopenias
Type III allergy (immune complex allergy): more common in exogenous serum, furazolidone, and penicillin; manifests as vasculitic drug eruption and serum sickness-like syndrome; the incubation period is generally longer
Type IV allergic reaction (delayed allergic reaction): manifested as erythrodermic drug eruption, measles-type drug eruption, and eczema-type drug eruption
Features:
① It only occurs in a small number of people with allergies, and most people do not react;
② There is a certain incubation period, and it usually takes 4 to 20 days for clinical manifestations to appear after the first administration of the drug; for those who have been sensitized, the onset of symptoms may occur within a few minutes to 24 hours if the drug is administered again;
③ There is no correlation between the severity of the disease and the pharmacological/toxicological effects and dosage of the drug. In a hypersensitive state, even a small dose of drugs can cause extremely serious drug rash;
④The clinical manifestations are complex and the skin lesions have different shapes. The same patient may have different types of drug eruptions at different times due to sensitization to the same drug;
⑤ Cross-allergy/polyvalent allergy to drugs occurs in a hypersensitive state;
⑥The course of the disease is self-limiting to a certain extent. The condition often improves after stopping allergenic drugs. Anti-allergic and glucocorticoid treatments are effective.
Photoallergic drug eruption: an allergic drug eruption caused by a small number of drugs entering the human body and converting into antigenic substances under the induction of light
Non-allergic
Pharmacological effects: For example, aspirin can directly induce mast cell degranulation and release histamine, causing urticaria. Drug interactions
Adverse drug reactions and dysbiosis
Overdose reaction and accumulation effects: such as liver and kidney insufficiency, slow drug excretion, and prolonged use of drugs
Defect/inhibition of enzymes involved in drug metabolism: e.g. phenytoin hypersensitivity syndrome (cyclooxygenase hydrolase deficiency) Drug exacerbating an existing skin disease
[Clinical manifestations] Pay attention to severe drug eruptions: severe erythema multiforme type, epidermolysis bullosa type, exfoliative dermatitis type DHS
Main types
Fixed (fixed) drug eruption: more common, often occurs at the junction of skin and mucous membranes (such as around the mouth and nose, external genitalia and perianal area). Each occurrence is often in the same location. It is common in antipyretic analgesics, sulfonamides, and antibiotics. Biturates and tetracyclines; manifested as localized round/oval edematous purple-red/bright red macules/patches with clear boundaries that subside after 1 to 10 days, leaving pigmentation; there is itching/pain, but the symptoms are normal No systemic symptoms
Urticarial drug eruption: more common, especially serum products, furazolidone, penicillin, and aspirin; manifests as generalized wheals, flushing and edema all over the body, and slow subsidence; angioedema may occur, accompanied by stinging and tenderness; also Serum sickness-like symptoms (fever, joint pain, lymphadenopathy, proteinuria) may occur; in severe cases, anaphylactic shock may occur
Exanthematous drug eruption/measles type or scarlet fever type drug eruption: the most common (90%); common in semi-synthetic penicillins, sulfonamides, antipyretic analgesics, barbiturates; often a few days after the first dose (not more than 2w) ) occurs; it manifests as measles-type/scarlet fever-type erythema/papule herpes fused into large areas, often symmetrically distributed on the trunk and limbs (the face is rarely involved), accompanied by fever, itching, and eosinophils↑; half of the disease course is 1 to 2 weeks , may be accompanied by bran-like desquamation after the skin lesions subside.
Drug-induced bullosa epidermolysis/drug-induced toxic epidermal necrolysis (TEN): the most serious, common in sulfonamides, antipyretic analgesics, antibiotics, and barbitol steroids, carbamazepine, allopurinol, and anti-tuberculosis drugs; the onset is sudden, manifested as diffuse erythema over the body, blisters of varying sizes quickly appearing, the blister walls are loose, Nissl's sign is positive, and large erosions form when rubbed. With exudation; skin tenderness is obvious; the mucous membranes of the eyes, mouth, nose, genitals, and anus are often involved, manifesting as congestive inflammation, erosion, and exudation, causing corresponding symptoms (such as photophobia, blurred vision, and oral pain that affects eating) ; Systemic poisoning symptoms are severe, and there may be significant internal organ damage
Exfoliative dermatitis type drug eruption (drug-induced exfoliative dermatitis): It is severe and is common in sulfonamides, barbiturates, anti-epileptic drugs, antipyretic analgesics, and antibiotics. It mostly occurs after long-term use of drugs; the incubation period of the onset is long ( More than 20 days), the condition worsens progressively; it starts out as measles-like/scarlet fever-like skin lesions, gradually worsens and merges into diffuse flushing and swelling all over the body (especially the face, hands and feet), accompanied by blisters, erosion, exudation, and scabs, which may There is a special odor; after 2 to 3 weeks, the redness and swelling gradually subside, and a large amount of scaly/leaf-like desquamation appears all over the body. The palms and toes peel off like gloves/socks, and the hair and fingernails may fall off; the oral mucosa and eye conjunctiva may be involved. ; Systemic symptoms are obvious
Other types
Eczema-type (eczematous) drug eruption: It is more common in local contact dermatitis caused by external use of penicillin and sulfa drugs, and then oral/injection of similar drugs, resulting in generalized eczema-like changes throughout the body.
Acneiform drug eruption: common in long-term use of halogen preparations, glucocorticoids, and birth control pills; manifests as follicular papules and papulopustules on the face/chest and back; the course of the disease is slow, and generally there are no systemic symptoms
Purpuric drug eruption: common in antibiotics, barbiturates, and diuretics; often occurs in both lower limbs, symmetrical on both sides, manifesting as needle-to-pea-sized petechiae/ecchymoses, scattered/densely distributed, slightly raised, and compressed It does not fade. In severe cases, it may be accompanied by joint swelling and pain, abdominal pain, hematuria, and blood in the stool.
Erythema multiforme drug eruption: common in sulfonamides, antipyretic analgesics, and barbiturates; divided into mild and severe types, with symptoms basically similar to erythema multiforme
photosensitive drug eruption
Commonly found in chlorpromazine, sulfonamides, tetracyclines, griseofulvin, psoralen, quinolones, phenothiazines, and contraceptive pills, and caused by sunlight/ultraviolet irradiation
Classification
Phototoxic reaction drug eruption: sunburn-like skin lesions appear on the exposed area after 7 to 8 hours of exposure; it can occur in anyone. The onset is related to the dose of the drug and the dose of radiation. It disappears quickly after stopping the drug.
Photoallergic drug eruption: only seen in a few people, has a certain incubation period, manifests as eczema-like skin lesions in exposed/non-exposed areas; the course of the disease is long
Drug hypersensitivity syndrome (DHS)/drug eruption with eosinophilia and systemic symptoms: usually occurs within 2 to 6 weeks after the first dose, and may occur within 1 day after re-administration. It is more common in epoxides Individuals with hydrolase deficiency; the inducing drugs are mainly anti-epileptic drugs and sulfonamides; manifested as skin lesions and visceral damage (such as lymphadenopathy, hepatitis, interstitial nephritis, interstitial pneumonia, myocarditis, fulminant liver damage is the main cause of death) Hematological abnormalities (eosinophils ≥1000/L, positive atypical lymphocytes)
Others: chloasma-like, skin pigmentation, SLE-like, lichen planus-like, pemphigus-like, pustular
【examine】
In vivo testing
Skin test, drug provocation test (only applicable to those with mild drug rash caused by oral drugs and the disease itself requires the use of the drug for treatment)
in vitro test
Higher security
【diagnosis】
① Have a clear history of medication;
②There is a certain incubation period between medication and onset of disease;
③The onset is acute, and the rash is often symmetrical and systemic (except for fixed drug eruptions);
④Exclude infectious diseases, other skin diseases or internal diseases with similar damage (generally, drug rash lesions are brighter in color, more itchy, and will gradually improve after stopping the drug)
【prevention】
① Ask the patient in detail whether he or she has a history of drug allergy before taking medication. When taking medication, do not choose drugs that have been allergic in the past or have a similar structure to the allergenic drugs or have cross-allergies;
②A skin test should be performed when using penicillin, serum products, procaine and other drugs. Emergency drugs should be prepared before the skin test. This drug is prohibited for those with positive skin tests;
③ Avoid drug abuse and reduce the number of medications used; adopt safe administration routes, and try to choose drugs with lower allergenicity for those with allergies, paying special attention to known allergy drugs contained in compound preparations;
④ Pay attention to the early symptoms of drug rash. If unexplained itching, erythema, fever, etc. suddenly appear during medication, all suspicious drugs should be stopped immediately and closely observed. Symptoms that have occurred should be properly handled;
⑤ Record known allergenic drugs on the home page of the patient’s medical record or create a drug contraindication card for the patient, and instruct the patient to remember it and inform the doctor before each medical visit
【treat】
Treatment principles
① Disable allergenic drugs;
②Accelerate the excretion of drugs (drink more water, intravenous infusion);
③Give anti-allergic and anti-inflammatory treatment, supportive treatment, and prevent secondary infection;
④Give different treatments according to the severity of the condition (see below for details)
Type treatment
Mild: When the rash and systemic symptoms are mild, only symptomatic treatment can be given
Antihistamines: such as Claritin
Vitamin C and calcium supplements
Low-dose prednisone: used when necessary; the dose can be gradually reduced after the skin lesions improve.
Topical water powder/cream: anti-itching and anti-inflammatory
Severe: Need to be hospitalized for rescue
Intravenous glucocorticoids: use as early as possible and in sufficient amount
∎ Pay attention to the prevention and treatment of secondary infections: one of the key measures; pay attention to good wound care and aseptic operation; when infection exists, antibiotics with less allergenicity should be used
Strengthen supportive care:
IVIg and plasma exchange if necessary
∎ Pay attention to the care of skin and mucous membranes: You can choose the dosage form according to the type of skin lesions; keep the mucous membranes of your eyes, mouth, and external genitalia clean, and apply anti-inflammatory solution or ointment
anaphylactic shock