Antihistamines in Dermatology — MCQs
A patient who experiences recurrent urticaria during exercise and heat exposure, including sunlight, most likely has:
All of the following statements are TRUE about second generation antihistaminic agents EXCEPT:
Second-generation cephalosporin that can be used orally is:
H1 antihistaminic having best topical activity is:
The skin condition shown in the image is associated with?
A patient developed fixed drug eruptions after taking certain medications. Which of the following drugs is known to cause these skin lesions?
Which of the following is a topical vitamin D analogue?
Which drug is used for intralesional injection in keloids?
Dapsone is used in which of the following conditions?
At the same concentration, which of the following vehicles is most potent for topical steroid delivery?
Antihistamines in Dermatology Indian Medical PG Practice Questions and MCQs
Question 1: A patient who experiences recurrent urticaria during exercise and heat exposure, including sunlight, most likely has:
- A. Chronic Spontaneous Urticaria
- B. Universal Dermographism
- C. Cholinergic Urticaria (Correct Answer)
- D. Photodermatitis
Explanation: ***Cholinergic Urticaria*** - Cholinergic urticaria is characterized by the appearance of small, itchy wheals in response to stimuli that raise the **body temperature**, such as **exercise**, **heat**, or **emotional stress**. - The symptoms resolve when the body cools down, aligning with the patient's presentation of recurrent urticaria during exercise and heat exposure. *Chronic Spontaneous Urticaria* - This condition involves daily or almost daily urticaria for **six weeks or more** without an identifiable external cause. - While it is chronic, the specific triggers of exercise and heat exposure point more directly to a physical urticaria like cholinergic urticaria. *Universal Dermographism* - **Dermographism** (or dermatographia) is a type of physical urticaria where hives appear after **firm stroking or scratching** of the skin. - Universal dermographism would imply this reaction over a large body surface area, but it is not typically triggered by systemic heat or exercise. *Photodermatitis* - **Photodermatitis** is a general term for skin inflammation caused by **exposure to light**, especially sunlight, often due to an abnormal reaction to UV radiation. - While sunlight is a trigger for this patient's symptoms, the additional triggers of exercise and general heat exposure make cholinergic urticaria a more encompassing diagnosis than photodermatitis alone.
Question 2: All of the following statements are TRUE about second generation antihistaminic agents EXCEPT:
- A. These may possess additional antiallergic mechanisms
- B. These do not impair psychomotor performance
- C. These lack anticholinergic actions
- D. These possess high anti-motion sickness activity (Correct Answer)
Explanation: ***These possess high anti-motion sickness activity*** - Second-generation antihistamines have **poor penetration** into the central nervous system (CNS), making them ineffective for treating **motion sickness**. - **First-generation antihistamines**, which readily cross the blood-brain barrier and have **anticholinergic activity**, are typically used for motion sickness. *These may possess additional antiallergic mechanisms* - Many second-generation antihistamines, such as **cetirizine** and **loratadine**, have additional anti-inflammatory and **antiallergic properties** beyond H1 receptor blockade. - These mechanisms can include inhibiting the release of inflammatory mediators and **stabilizing mast cells**. *These do not impair psychomotor performance* - Second-generation antihistamines are **non-sedating** because they have limited ability to cross the **blood-brain barrier** and thus do not significantly affect CNS function. - This characteristic makes them suitable for use without causing **drowsiness** or impairing activities like driving. *These lack anticholinergic actions* - Unlike first-generation antihistamines, second-generation agents have **minimal to no affinity** for muscarinic acetylcholine receptors. - This lack of **anticholinergic activity** means they do not cause side effects such as **dry mouth**, blurred vision, or urinary retention.
Question 3: Second-generation cephalosporin that can be used orally is:
- A. Cefepime
- B. Cefalothin
- C. Cefaclor (Correct Answer)
- D. Cefadroxil
Explanation: ***Cefaclor*** - **Cefaclor** is a commonly used **second-generation cephalosporin** that is available in an **oral formulation**, making it suitable for outpatient treatment of various bacterial infections. - Its spectrum of activity includes many Gram-positive and Gram-negative bacteria, often used for **respiratory tract infections** and **otitis media**. *Cefepime* - **Cefepime** is a **fourth-generation cephalosporin**, not a second-generation one, and is primarily administered **intravenously** for severe infections. - It has a broader spectrum against both Gram-positive and Gram-negative bacteria, including **Pseudomonas aeruginosa**. *Cefalothin* - **Cefalothin** (also known as cephalothin) is a **first-generation cephalosporin** that is typically administered **parenterally** (intravenously or intramuscularly). - It is not available in an oral formulation, limiting its use to hospital settings for moderate to severe infections. *Cefadroxil* - **Cefadroxil** is a **first-generation cephalosporin** and is available for oral administration. - While it is an oral cephalosporin, it belongs to the first generation, not the second generation as requested by the question.
Question 4: H1 antihistaminic having best topical activity is:
- A. Loratadine
- B. Astemizole
- C. Cetirizine
- D. Azelastine (Correct Answer)
Explanation: **Azelastine (Correct Answer)** - **Azelastine** is an H1 antihistamine available as a **nasal spray** and **eye drops**, demonstrating excellent topical activity. - Its **lipophilicity** and local action make it highly effective for treating allergic rhinitis and conjunctivitis, with minimal systemic absorption. *Loratadine* - **Loratadine** is an oral, second-generation H1 antihistamine primarily used for systemic treatment of allergies. - It does not possess significant topical activity for local application in the nose or eyes. *Astemizole* - **Astemizole** is a second-generation H1 antihistamine that was withdrawn from the market due to significant **cardiac toxicity**, including QTc prolongation and torsades de pointes. - It was an oral medication and did not have widespread topical formulations. *Cetirizine* - **Cetirizine** is an oral H1 antihistamine known for its potency and relatively quick onset of action. - Although it can be used for systemic allergy relief, it is not primarily formulated or recognized for its topical efficacy compared to azelastine.
Question 5: The skin condition shown in the image is associated with?
- A. Diabetes mellitus (Correct Answer)
- B. Hypothyroidism
- C. Hyperthyroidism
- D. Sarcoidosis
Explanation: ***Diabetes mellitus*** - The image shows **diabetic dermopathy** (also known as "shin spots"), which presents as hyperpigmented, atrophic macules or papules, usually on the shins. This condition is a common cutaneous manifestation of **diabetes mellitus**. - Other dermatological conditions associated with diabetes include **necrobiosis lipoidica diabeticorum**, **acanthosis nigricans**, and **erythrasma**, which are important to recognize in patients with diabetes. *Hypothyroidism* - Hypothyroidism is associated with **myxedema**, which typically manifests as non-pitting edema, dry and coarse skin, and hair loss. - While it can cause skin changes, it does not typically present with the pigmented, atrophic lesions seen in the image. *Hyperthyroidism* - Hyperthyroidism can cause skin changes such as **pretibial myxedema** (a specific form of localized skin thickening, typically on the shins, that is often associated with Graves' disease) and warm, moist skin due to increased metabolism. - The lesions shown in the image are not consistent with the typical presentation of pretibial myxedema or other hyperthyroid skin manifestations. *Sarcoidosis* - Sarcoidosis can present with various skin lesions, including **erythema nodosum**, lupus pernio, plaques, and papules. - The skin changes seen in the image, characterized by small, atrophic, hyperpigmented macules, do not fit the typical pattern of cutaneous sarcoidosis.
Question 6: A patient developed fixed drug eruptions after taking certain medications. Which of the following drugs is known to cause these skin lesions?
- A. Phenolphthalein
- B. Aspirin
- C. Dapsone
- D. All of the above (Correct Answer)
Explanation: **Explanation:** **Fixed Drug Eruption (FDE)** is a unique type of cutaneous drug reaction characterized by the recurrence of a lesion (usually a dusky red or violaceous macule) at the **exact same anatomical site** every time the offending drug is ingested. This occurs due to the persistence of **CD8+ memory T-cells** in the basal keratinocytes at the site of the lesion. **Why Option D is correct:** All three drugs listed are classic and high-yield triggers for FDE: * **Phenolphthalein:** Historically the most common cause (found in older laxatives). * **Aspirin (NSAIDs):** A very frequent trigger in clinical practice. * **Dapsone (Sulfonamides):** Sulfonamides are among the most common drug classes associated with FDE. **Analysis of Options:** * **Phenolphthalein:** Often presents as "bullous" FDE. * **Aspirin:** Along with other NSAIDs (like Ibuprofen and Naproxen), it is a leading cause of multi-focal FDE. * **Dapsone:** As a sulfone, it shares cross-reactivity patterns and is a well-documented cause. **High-Yield Clinical Pearls for NEET-PG:** 1. **Most Common Site:** The **glans penis** is the most common site for FDE, followed by the lips and palms. 2. **Commonest Causes (Overall):** NSAIDs, Sulfonamides (Cotrimoxazole), Tetracyclines, and Anticonvulsants. 3. **Clinical Feature:** Lesions often leave behind **post-inflammatory hyperpigmentation (PIH)** after healing. 4. **Refractory Period:** After an eruption, there is a brief refractory period where the drug may not cause a reaction. 5. **Diagnosis:** Primarily clinical; however, a **Patch Test** performed at the site of the previous lesion (not on the back) can confirm the offending agent.
Question 7: Which of the following is a topical vitamin D analogue?
- A. Cholecalciferol
- B. Doxercalciferol
- C. Calcipotriol (Correct Answer)
- D. Paricalcitol
Explanation: **Explanation:** **Calcipotriol** is a synthetic analog of **1,25-dihydroxyvitamin D3 (Calcitriol)**. In dermatology, it is primarily used as a first-line topical treatment for **Psoriasis vulgaris**. Its mechanism of action involves binding to intracellular vitamin D receptors (VDR), leading to the inhibition of keratinocyte proliferation and the induction of keratinocyte differentiation. It also possesses anti-inflammatory properties by inhibiting T-cell activation. **Analysis of Options:** * **Calcipotriol (Correct):** It is specifically designed for topical use. It is as effective as potent topical corticosteroids but has a better safety profile for long-term maintenance, as it does not cause skin atrophy. * **Cholecalciferol (Option A):** This is Vitamin D3, typically administered orally as a nutritional supplement to treat Vitamin D deficiency. * **Doxercalciferol (Option B) & Paricalcitol (Option D):** These are synthetic Vitamin D analogs administered **systemically** (oral or IV). They are primarily used in the management of secondary hyperparathyroidism in patients with chronic kidney disease (CKD). **High-Yield Clinical Pearls for NEET-PG:** * **Combination Therapy:** Calcipotriol is frequently combined with **Betamethasone dipropionate** (e.g., Daivobet) for synergistic effects in psoriasis. * **Side Effects:** The most common side effect is local skin irritation. Systemic hypercalcemia is rare unless the dose exceeds **100g per week**. * **Contraindication:** It should not be applied to the face (due to irritation) and is generally avoided in patients with pre-existing hypercalcemia. * **Other Topical Analogs:** Tacalcitol and Maxacalcitol are other topical analogs used globally.
Question 8: Which drug is used for intralesional injection in keloids?
- A. Prednisolone
- B. Triamcinolone (Correct Answer)
- C. Androgen
- D. Hydrocortisone
Explanation: **Explanation:** **Triamcinolone acetonide (TAC)** is the gold standard and most commonly used drug for the intralesional treatment of keloids and hypertrophic scars. **Why Triamcinolone is the Correct Answer:** Triamcinolone is a potent, intermediate-acting synthetic corticosteroid. It works by: 1. **Inhibiting Fibroblasts:** It reduces the proliferation of fibroblasts and the synthesis of collagen. 2. **Anti-inflammatory Action:** It decreases the release of inflammatory mediators (like TGF-β) that drive excessive scarring. 3. **Increasing Collagenase:** It reduces levels of alpha-2-macroglobulin, which normally inhibits collagenase, thereby promoting the breakdown of existing collagen. The concentration typically used is **10–40 mg/mL**, injected directly into the mid-dermis of the lesion. **Analysis of Incorrect Options:** * **A & D (Prednisolone & Hydrocortisone):** These are shorter-acting corticosteroids with lower potency. They are highly soluble and rapidly absorbed into the systemic circulation, making them ineffective for maintaining the sustained local concentration required to break down dense keloidal tissue. * **C (Androgen):** Androgens have no role in the treatment of keloids; in fact, hormonal fluctuations (like puberty or pregnancy) are sometimes associated with keloid exacerbation. **High-Yield Clinical Pearls for NEET-PG:** * **Side Effects:** The most common side effects of intralesional TAC include **dermal atrophy, telangiectasia, and hypopigmentation** at the injection site. * **Combination Therapy:** For resistant keloids, TAC is often combined with **5-Fluorouracil (5-FU)** to improve efficacy and reduce atrophy. * **Cryosurgery:** Performing cryotherapy immediately before injection (the "cryo-insult" technique) softens the keloid, making the injection easier and more effective.
Question 9: Dapsone is used in which of the following conditions?
- A. Dermatitis herpetiformis (Correct Answer)
- B. Pityriasis rosacea
- C. Contact dermatitis
- D. Oculocutaneous albinism
Explanation: **Explanation:** **Dapsone (Diaminodiphenyl sulfone)** is the drug of choice for **Dermatitis Herpetiformis (DH)**. DH is an autoimmune blistering disorder characterized by IgA deposits at the dermal papillae, leading to intense pruritus and neutrophilic infiltration. Dapsone works by inhibiting the enzyme myeloperoxidase and preventing the chemotaxis of neutrophils to the skin, providing rapid symptomatic relief (often within 24–48 hours). **Analysis of Options:** * **A. Dermatitis Herpetiformis:** Correct. It is the primary indication for Dapsone in dermatology. * **B. Pityriasis Rosea:** This is a self-limiting inflammatory condition (likely viral/HHV-6,7). Treatment is supportive (antihistamines, topical steroids); Dapsone has no role. * **C. Contact Dermatitis:** This is a Type IV hypersensitivity reaction. Management involves allergen avoidance and topical or systemic corticosteroids. * **D. Oculocutaneous Albinism:** This is a genetic disorder of melanin synthesis. There is no pharmacological "cure"; management focuses on photoprotection and monitoring for skin cancers. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Action:** Antifolate (inhibits dihydropteroate synthase) and anti-inflammatory (inhibits neutrophil recruitment). * **Other Indications:** Leprosy (part of MDT), Pemphigoid, Subcorneal Pustular Dermatosis (Sneddon-Wilkinson disease), and Brown Recluse spider bites. * **Mandatory Pre-screening:** Always check **G6PD levels** before starting Dapsone to prevent severe **hemolytic anemia**. * **Side Effects:** Dose-dependent hemolysis, methemoglobinemia (presents as cyanosis), and the "Dapsone Syndrome" (fever, malaise, exfoliative dermatitis, and hepatitis).
Question 10: At the same concentration, which of the following vehicles is most potent for topical steroid delivery?
- A. Ointment (Correct Answer)
- B. Lotion
- C. Cream
- D. Gel
Explanation: **Explanation:** The potency of a topical corticosteroid is determined not only by the active pharmaceutical ingredient but also by its **vehicle**. The vehicle influences the rate of absorption and the depth of penetration into the skin. **Why Ointment is the Correct Answer:** Ointments are primarily oil-based (water-in-oil emulsions) and provide the highest level of **occlusion**. By forming a greasy film on the skin surface, they prevent transepidermal water loss, leading to increased hydration of the stratum corneum. Hydrated skin is significantly more permeable, allowing for maximum penetration of the steroid. Therefore, at the same concentration, an ointment is always more potent than a cream or lotion. **Why Other Options are Incorrect:** * **B. Lotion:** These are liquid-based (often water-based) and evaporate quickly. They have the least occlusive property and thus the lowest potency. They are preferred for hairy areas or oozing lesions. * **C. Cream:** These are oil-in-water emulsions. While they are more cosmetically elegant and easier to wash off, they provide less occlusion than ointments, resulting in moderate potency. * **D. Gel:** Gels are transparent, non-greasy formulations. While they are excellent for the scalp and oily skin, they lack the occlusive "barrier effect" required to match the potency of an ointment. **High-Yield Clinical Pearls for NEET-PG:** * **Rule of Thumb:** Potency ranking by vehicle: **Ointment > Cream > Lotion.** * **Absorption:** Steroid absorption is highest in areas with thin stratum corneum (e.g., eyelids, scrotum, face) and lowest in thick areas (e.g., palms, soles). * **Clinical Choice:** Use **ointments** for dry, thick, or hyperkeratotic lesions (e.g., chronic plaque psoriasis) and **creams/lotions** for moist, intertriginous, or weeping lesions. * **Finger Tip Unit (FTU):** One FTU (0.5g) is enough to cover the area of two adult palms.
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