Drug Allergies — MCQs
First line therapy in anaphylactic shock is:
A 45-year-old patient with a known allergy to penicillin presents with an enterococcal endocarditis. The physician needs to prescribe an antibiotic but wants to ensure it is safe for a penicillin allergy. The patient has had previous allergic reactions to penicillin including rash & swelling. Which of the following drugs can be used safely in a patient allergic to penicillin?
A patient presents with painful oral ulcers and target lesions on extremities. Which drug is MOST likely to cause this condition?
All of the following can cause SLE-like syndrome except
A patient comes to you with skin reactions after visiting the hair dresser. What will you do to confirm the diagnosis of contact dermatitis?
Which of the following drugs can cause hypotension by releasing histamine from mast cells?
A 45-year-old patient with a known allergy to penicillin presents with an enterococcal endocarditis. The physician needs to prescribe an antibiotic but wants to ensure it is safe for a penicillin allergy. The patient has had previous allergic reactions to penicillin including rash & swelling. Which of the following drugs can be used safely in a patient allergic to penicillin?
Drug of choice for Enterococcus infection in a patient allergic to penicillin?
Drug of choice for Enterococcus infection in a patient allergic to penicillin:
What is a characteristic feature of Systemic Juvenile Idiopathic Arthritis?
Drug Allergies Indian Medical PG Practice Questions and MCQs
Question 1: First line therapy in anaphylactic shock is:
- A. Epinephrine .5 ml of 1:1000 IM (Correct Answer)
- B. Atropine 3 mg intravenously
- C. Adenosine 12 mg intravenously
- D. Epinephrine 1 ml of 1:10000 intravenously
Explanation: ***Epinephrine .5 ml of 1:1000 IM*** - **Epinephrine** is the **first-line treatment** for anaphylaxis due to its alpha-1 agonist effects (vasoconstriction, which increases blood pressure) and beta-2 agonist effects (bronchodilation, which improves breathing). [1] - The recommended dose and concentration for intramuscular administration in adults is **0.3-0.5 mg (0.3-0.5 mL of 1:1000 solution) IM**, repeated every 5-15 minutes as needed. *Atropine 3 mg intravenously* - **Atropine** is an anticholinergic medication used to treat **bradycardia** or organophosphate poisoning, not anaphylaxis. [4] - It does not address the widespread vasaodilation or bronchoconstriction seen in anaphylactic shock. *Adenosine 12 mg intravenously* - **Adenosine** is an antiarrhythmic drug primarily used to convert **supraventricular tachycardia (SVT)** to normal sinus rhythm. [3] - It has no role in the management of anaphylactic shock. *Epinephrine 1 ml of 1:10000 intravenously* - While epinephrine is the correct drug, **intravenous administration** of epinephrine 1:10,000 is typically reserved for **cardiac arrest** [2] or in cases of severe, refractory anaphylaxis under expert care, and carries a higher risk of adverse effects. - The initial and preferred route for anaphylaxis is **intramuscular**, as it provides rapid absorption with lower risks compared to IM administration.
Question 2: A 45-year-old patient with a known allergy to penicillin presents with an enterococcal endocarditis. The physician needs to prescribe an antibiotic but wants to ensure it is safe for a penicillin allergy. The patient has had previous allergic reactions to penicillin including rash & swelling. Which of the following drugs can be used safely in a patient allergic to penicillin?
- A. Ceftriaxone
- B. Vancomycin (Correct Answer)
- C. Piperacillin
- D. Aztreonam
Explanation: ***Vancomycin*** - **Vancomycin** is a glycopeptide antibiotic with a completely different mechanism of action and chemical structure compared to penicillins, making it **safe for patients with penicillin allergy**. - It is the **first-line treatment for enterococcal endocarditis** in patients with penicillin allergy, providing excellent coverage against both *Enterococcus faecalis* and *E. faecium*. - No cross-reactivity with beta-lactam antibiotics. *Ceftriaxone* - **Ceftriaxone** is a third-generation **cephalosporin**, a beta-lactam antibiotic with structural similarity to penicillin. - There is **5-10% cross-reactivity risk** in patients with IgE-mediated penicillin allergy (rash, swelling, anaphylaxis), making it potentially unsafe in this patient. - Should be avoided in patients with a history of immediate hypersensitivity reactions to penicillin. *Piperacillin* - **Piperacillin** is a **penicillin derivative** (ureidopenicillin) and shares the same beta-lactam core structure that triggers allergic reactions. - **Absolutely contraindicated** in patients with known penicillin allergy—would almost certainly provoke an allergic reaction. - Using this drug would expose the patient to significant risk of anaphylaxis. *Aztreonam* - **Aztreonam** is a **monobactam** with minimal cross-reactivity (<1%) with penicillins and is generally **safe for penicillin-allergic patients** from an allergy perspective. - However, aztreonam has **primarily gram-negative coverage** and **poor activity against enterococci**, making it ineffective for treating enterococcal endocarditis. - While safe regarding allergy concerns, it is not the appropriate choice due to **lack of efficacy** against the causative organism.
Question 3: A patient presents with painful oral ulcers and target lesions on extremities. Which drug is MOST likely to cause this condition?
- A. Metformin
- B. Allopurinol (Correct Answer)
- C. Atorvastatin
- D. Amlodipine
Explanation: ***Allopurinol*** - **Allopurinol** is a well-known cause of drug-induced **Stevens-Johnson Syndrome (SJS)** or **Toxic Epidermal Necrolysis (TEN)**, which presents with typical mucocutaneous lesions like painful oral ulcers and target lesions on the skin. - The drug is frequently implicated, especially in patients with **renal impairment** or those started on high doses, making it the most likely choice given the severe symptoms. *Metformin* - **Metformin** is a common medication for type 2 diabetes, primarily causing **gastrointestinal side effects** like nausea, diarrhea, and abdominal discomfort. - It is **rarely associated** with severe cutaneous adverse reactions like SJS/TEN. *Atorvastatin* - **Atorvastatin** is a statin commonly used for hyperlipidemia, and its most common side effects include **myalgia**, headache, and gastrointestinal issues. - While it can rarely cause *rashes*, it is **not a typical or frequent cause** of severe mucocutaneous reactions such as target lesions or painful oral ulcers characteristic of SJS/TEN. *Amlodipine* - **Amlodipine**, a calcium channel blocker, is typically associated with side effects such as **edema**, headache, and flushing. - Although drug eruptions can occur with amlodipine, **severe mucocutaneous reactions** like SJS/TEN presenting with target lesions and oral ulcers are **exceedingly rare** and not characteristic of this drug.
Question 4: All of the following can cause SLE-like syndrome except
- A. Isoniazid
- B. Hydralazine
- C. Penicillin (Correct Answer)
- D. Sulphonamide
Explanation: ***Penicillin*** - Penicillin is known to cause **drug-induced hemolytic anemia**, **allergic reactions**, and **serum sickness-like reactions**, but not typically an SLE-like syndrome. - While it can induce certain autoimmune phenomena, it does not commonly trigger the specific constellation of symptoms and autoantibodies associated with drug-induced lupus. *Isoniazid* - **Isoniazid** is a well-known cause of **drug-induced lupus erythematosus**, particularly in slow acetylators. - It can lead to positive **antinuclear antibodies (ANAs)** and clinical symptoms mimicking SLE. *Hydralazine* - **Hydralazine** is a classic drug associated with **drug-induced lupus**, often presenting with **arthralgias**, **myalgias**, and **fever**. - It commonly induces **anti-histone antibodies** and **ANA** without significant renal or central nervous system involvement. *Sulphonamide* - **Sulfonamides** (such as sulfasalazine) can induce an **SLE-like syndrome** and are recognized causes of drug-induced lupus. - They are associated with the development of **autoantibodies** and systemic symptoms similar to spontaneous SLE.
Question 5: A patient comes to you with skin reactions after visiting the hair dresser. What will you do to confirm the diagnosis of contact dermatitis?
- A. S IgE
- B. Allergy Test
- C. Patch Test (Correct Answer)
- D. VDRL
Explanation: ***Patch Test*** - A **patch test** is the gold standard for diagnosing **allergic contact dermatitis** by directly applying suspected allergens to the skin. - This test identifies specific substances that cause a delayed hypersensitivity reaction, which is characteristic of contact dermatitis. *S IgE* - **Serum IgE** levels are primarily indicative of **Type I hypersensitivity** reactions, such as allergic rhinitis or asthma. - Contact dermatitis is a **Type IV delayed hypersensitivity reaction**, not mediated by IgE antibodies. *Allergy Test* - The term "allergy test" is broad and can refer to various methods including skin prick tests, IgE blood tests, or patch tests. - Without specifying **patch testing**, other forms of allergy tests are less appropriate for diagnosing contact dermatitis, as they target different immune mechanisms. *VDRL* - **VDRL (Venereal Disease Research Laboratory)** test is used to screen for **syphilis**, a sexually transmitted infection. - It has no relevance to the diagnosis of contact dermatitis, which is an inflammatory skin condition caused by contact with an allergen or irritant.
Question 6: Which of the following drugs can cause hypotension by releasing histamine from mast cells?
- A. Morphine (Correct Answer)
- B. Sulfadiazine
- C. Procaine
- D. Aspirin
Explanation: ***Correct Option - Morphine*** **Morphine** and other opioids can cause **non-immunologic histamine release** from mast cells, leading to **vasodilation**, bronchoconstriction, and systemic hypotension. - The release of histamine directly causes a decrease in **peripheral vascular resistance**, contributing to a drop in blood pressure - This is a **direct pharmacological effect**, not an allergic reaction - Other opioids with similar effects include **codeine** and **meperidine** *Incorrect Option - Procaine* **Procaine** is a local anesthetic that can cause hypotension primarily due to its **direct vasodilatory effect** and cardiovascular depression, rather than histamine release. - While allergic reactions to procaine (which involve histamine) can occur, hypotension in this context is usually related to **systemic absorption** and cardiovascular depression - The mechanism is NOT direct mast cell degranulation *Incorrect Option - Sulfadiazine* **Sulfadiazine** is an antibiotic that may cause hypotension as part of an **allergic reaction** (e.g., anaphylaxis), which would involve histamine. - However, it does not typically cause **direct, non-immunologic histamine release** from mast cells as a primary mechanism - Any histamine release would be **immunologic** (allergic), not direct pharmacological mast cell degranulation *Incorrect Option - Aspirin* **Aspirin** (acetylsalicylic acid) can cause significant hypotension in cases of **overdose** or severe intolerance. - Primary mechanism involves **prostaglandin synthesis inhibition**, which can influence vascular tone - May cause cardiovascular depression in overdose - Does NOT cause direct histamine release from mast cells
Question 7: A 45-year-old patient with a known allergy to penicillin presents with an enterococcal endocarditis. The physician needs to prescribe an antibiotic but wants to ensure it is safe for a penicillin allergy. The patient has had previous allergic reactions to penicillin including rash & swelling. Which of the following drugs can be used safely in a patient allergic to penicillin?
- A. Ceftriaxone
- B. Piperacillin
- C. Vancomycin (Correct Answer)
- D. Aztreonam
Explanation: ***Vancomycin***- **Vancomycin** is a glycopeptide antibiotic that is **structurally unrelated to penicillin**, with no cross-reactivity in penicillin-allergic patients [2].- It has **excellent activity against Enterococcus species** and is the **preferred alternative for enterococcal endocarditis** in patients with penicillin allergy [1, 2].- Vancomycin provides reliable bactericidal activity against enterococci and is guideline-recommended for this indication in penicillin-allergic patients [1].*Aztreonam*- **Aztreonam** is a monobactam antibiotic with minimal cross-reactivity to penicillin allergies due to its unique beta-lactam structure.- However, aztreonam has **NO activity against Gram-positive organisms**, including Enterococcus species.- It would be **completely ineffective** for treating enterococcal endocarditis despite being safe in penicillin allergy.*Ceftriaxone*- **Ceftriaxone** is a third-generation cephalosporin that shares the beta-lactam ring structure with penicillins.- There is approximately **1-3% cross-reactivity risk** in patients with non-severe penicillin allergy, and up to 10% in those with severe reactions [1].- Given this patient's history of rash and swelling, ceftriaxone carries **unacceptable cross-reactivity risk** [1].*Piperacillin*- **Piperacillin** is an extended-spectrum penicillin antibiotic, belonging to the same drug class as penicillin [1].- It is **absolutely contraindicated** in penicillin-allergic patients due to identical allergenic epitopes [1].- Administration would carry a **high risk of severe allergic reaction**, including potential anaphylaxis [1].
Question 8: Drug of choice for Enterococcus infection in a patient allergic to penicillin?
- A. Streptomycin
- B. Cephalosporin
- C. Vancomycin (Correct Answer)
- D. Rifampicin
Explanation: ***Vancomycin*** - **Vancomycin** is a glycopeptide antibiotic that is effective against **Gram-positive bacteria**, including *Enterococcus*, especially in patients with a **penicillin allergy**. - It inhibits **cell wall synthesis** by binding to the D-Ala-D-Ala terminus of peptidoglycan precursors, a different mechanism from penicillins. *Streptomycin* - **Streptomycin** is an aminoglycoside that inhibits **protein synthesis** and is primarily used in **combination therapy** for serious *Enterococcal* infections, but typically alongside a cell-wall active agent (like penicillin or vancomycin) for synergistic killing in endocarditis or other severe infections. - It is not usually recommended as a **monotherapy** for *Enterococcus*, especially in the context of penicillin allergy, as it doesn't provide bactericidal activity on its own against all enterococcal strains. *Cephalosporin* - **Cephalosporins** are **not active** against *Enterococcus spp.* as these bacteria intrinsically lack the **penicillin-binding proteins (PBPs)** that cephalosporins target effectively. - This **intrinsic resistance** makes cephalosporins an inappropriate choice for treating *Enterococcal* infections, regardless of penicillin allergy status. *Rifampicin* - **Rifampicin** is an antibiotic primarily used for **Mycobacterial infections** (e.g., tuberculosis) and some **Staphylococcal infections**, often in combination to prevent resistance. - It has **poor activity** against *Enterococcus* and is not a recommended treatment for *Enterococcal* infections.
Question 9: Drug of choice for Enterococcus infection in a patient allergic to penicillin:
- A. Rifampicin
- B. Vancomycin (Correct Answer)
- C. Streptomycin
- D. Cephalosporin
Explanation: ***Vancomycin*** - As a **glycopeptide antibiotic**, **vancomycin** is a primary treatment for **Enterococcus infections** when a penicillin allergy is present [3] or the strain is resistant to beta-lactams [1]. - It works by inhibiting **cell wall synthesis** at a different site than penicillin [2], making it effective against gram-positive bacteria like Enterococcus [4]. *Rifampicin* - **Rifampicin** is primarily used for **tuberculosis** and other mycobacterial infections, or in combination therapy for staphylococcal infections. - It is **not a first-line agent** for uncomplicated Enterococcus infections due to concerns about resistance development when used alone and its limited spectrum against Enterococcus. *Streptomycin* - **Streptomycin** is an **aminoglycoside antibiotic** and is typically used in combination with a cell-wall active agent (like penicillin or vancomycin) for synergistic killing in severe **Enterococcal endocarditis** [4]. - It is **not effective as monotherapy** for Enterococcus and often requires susceptibility testing due to widespread resistance if used alone [4]. *Cephalosporin* - **Cephalosporins** generally have **poor activity** against Enterococcus species, as Enterococci inherently possess acquired or intrinsic resistance mechanisms. - Therefore, cephalosporins are **not recommended** for treating Enterococcal infections, even in the absence of a penicillin allergy.
Question 10: What is a characteristic feature of Systemic Juvenile Idiopathic Arthritis?
- A. Uveitis is a feature
- B. It occurs after 16 years of age
- C. NSAIDs are contraindicated
- D. RA factor is negative (Correct Answer)
Explanation: ### Explanation **Systemic Juvenile Idiopathic Arthritis (sJIA)**, also known as Still’s disease, is a unique subtype of JIA characterized by prominent extra-articular features. **Why the correct answer is right:** In sJIA, the **Rheumatoid Factor (RF) is characteristically negative**. Unlike the polyarticular subtype (which can be RF positive), sJIA is considered an autoinflammatory disease rather than a classic autoimmune disease. Diagnosis is clinical, based on the presence of arthritis in one or more joints associated with (or preceded by) a fever of at least 2 weeks' duration that is daily ("quotidian") for at least 3 days, accompanied by features like an evanescent salmon-pink rash, lymphadenopathy, or serositis. **Analysis of Incorrect Options:** * **A. Uveitis is a feature:** This is incorrect for sJIA. Chronic anterior uveitis is a classic complication of **Oligoarticular JIA** (especially if ANA positive). Uveitis is very rare in the systemic subtype. * **B. It occurs after 16 years of age:** By definition, JIA must have an onset **before the age of 16**. If similar symptoms occur after 16, it is termed Adult-Onset Still’s Disease (AOSD). * **C. NSAIDs are contraindicated:** This is false. NSAIDs are often the **first-line** symptomatic treatment for pain and fever in JIA, though systemic steroids or biologics (IL-1 and IL-6 inhibitors) are usually required for definitive control. **High-Yield Clinical Pearls for NEET-PG:** * **Fever Pattern:** Classic "Quotidian" fever (spikes once daily, usually in the evening, returning to baseline). * **Laboratory Markers:** Marked leukocytosis, thrombocytosis, and highly elevated ESR/CRP. * **Ferritin:** Extremely high ferritin levels are common and can signal the onset of **Macrophage Activation Syndrome (MAS)**, a life-threatening complication of sJIA. * **Biologics of Choice:** Tocilizumab (IL-6 inhibitor) and Anakinra/Canakinumab (IL-1 inhibitors).
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