Dermatological Pharmacology — MCQs

Dermatological Pharmacology Indian Medical PG Practice Questions and MCQs

Question 11: What is the daily dose of thalidomide for controlling Erythema Nodosum Leprosum (ENL)?

A. 100 mg
B. 200-300 mg (Correct Answer)
C. 500 mg
D. 1000 mg

Explanation: **Explanation:** **Erythema Nodosum Leprosum (ENL)**, or Type 2 Lepra reaction, is a Type III hypersensitivity reaction characterized by painful subcutaneous nodules, fever, and systemic involvement. **Thalidomide** is considered the drug of choice for chronic or recurrent ENL due to its potent anti-TNF-α properties and its ability to inhibit neutrophil chemotaxis. 1. **Why 200-300 mg is correct:** The standard therapeutic dose for controlling an acute episode of ENL is **100 mg to 300 mg daily**, usually administered at bedtime. Most clinical guidelines (including WHO and IAL) recommend starting at **300 mg/day** for severe reactions to achieve rapid suppression of inflammation, followed by a gradual tapering once the reaction is controlled. 2. **Why other options are incorrect:** * **100 mg:** While 100 mg can be used for very mild cases or as a maintenance dose during tapering, it is often insufficient to control an acute, severe ENL flare. * **500 mg & 1000 mg:** These doses are excessively high and significantly increase the risk of dose-dependent toxicity (peripheral neuropathy and sedation) without providing additional therapeutic benefit for ENL. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Action:** Primarily acts by inhibiting **TNF-alpha**. * **Teratogenicity:** Thalidomide is notorious for causing **Phocomelia** (seal-like limbs). It is strictly contraindicated in pregnancy (Category X). * **Side Effects:** The most common side effect is **somnolence**; the most serious long-term side effect is **irreversible peripheral neuropathy**. * **Regulatory Note:** Due to its teratogenic potential, it is distributed under the **STEPS** (System for Thalidomide Education and Prescribing Safety) program.

Question 12: Castellani's paint contains all of the following ingredients except?

A. Basic fuchsin
B. Phenol
C. Benzene hexachloride (Correct Answer)
D. Boric acid

Explanation: **Explanation:** **Castellani’s Paint** (also known as Carbol-Fuchsin solution) is a classic topical formulation used in dermatology primarily for its antifungal, antibacterial, and drying properties. 1. **Why Benzene Hexachloride is the correct answer:** Benzene hexachloride (Lindane) is an **ectoparasiticide** used to treat scabies and lice. It is not a component of Castellani’s paint. The paint is designed to treat fungal infections (like Tinea cruris or intertrigo) and bacterial overgrowth, not parasitic infestations. 2. **Analysis of Incorrect Options (Components of Castellani’s Paint):** * **Basic Fuchsin (Option A):** This is the primary active dye that gives the paint its characteristic deep red/magenta color. It provides potent antifungal and antiseptic action. * **Phenol (Option B):** Acts as a preservative and a local anesthetic/antipruritic agent, helping to relieve itching associated with skin infections. * **Boric Acid (Option C):** Serves as a mild antiseptic and helps maintain the acidic pH of the solution, which inhibits bacterial growth. * *Note:* Other standard ingredients include **Resorcinol** (keratolytic), **Acetone**, and **Alcohol**. **High-Yield Clinical Pearls for NEET-PG:** * **Indications:** It is highly effective for **Intertrigo**, **Erythrasma** (caused by *Corynebacterium minutissimum*), and localized **Tinea pedis**. * **The "Colorless" Variant:** Modern versions may omit Basic Fuchsin to avoid the permanent staining of clothes, though this reduces the antifungal efficacy. * **Side Effects:** It can cause localized irritation and, if applied over large denuded areas, phenol toxicity may occur. * **Key Identification:** In exams, remember the "deep red stain" mnemonic—Castellani’s Paint = Carbol-Fuchsin.

Question 13: Which of the following is given in the form of an intralesional injection to treat keloid?

A. Heparin
B. Triamcinolone (Correct Answer)
C. Danazol
D. Hydrocortisone

Explanation: **Explanation:** **1. Why Triamcinolone is Correct:** Intralesional corticosteroid injection is the **first-line treatment** for keloids and hypertrophic scars. **Triamcinolone acetonide (TAC)**, typically in concentrations of 10–40 mg/mL, is the preferred agent. It works by: * **Inhibiting Inflammation:** Reducing the recruitment of inflammatory cells. * **Reducing Collagen Synthesis:** Inhibiting fibroblast proliferation and suppressing the expression of genes responsible for collagen production. * **Increasing Collagenase Activity:** Promoting the breakdown of existing excess collagen fibers, thereby flattening the lesion. **2. Why Other Options are Incorrect:** * **A. Heparin:** While some experimental studies suggest heparin may inhibit fibroblast growth, it is not a standard clinical treatment for keloids. * **C. Danazol:** This is a synthetic androgen used primarily for endometriosis and hereditary angioedema; it has no role in the intralesional treatment of keloids. * **D. Hydrocortisone:** Although a corticosteroid, hydrocortisone is a low-potency, short-acting steroid. It is less effective and more soluble than Triamcinolone, making it unsuitable for providing the sustained local effect required to remodel dense keloid tissue. **3. NEET-PG High-Yield Pearls:** * **Side Effects of IL-TAC:** Dermal atrophy, telangiectasia, and hypopigmentation at the injection site. * **Combination Therapy:** For resistant keloids, Triamcinolone is often combined with **5-Fluorouracil (5-FU)** to improve efficacy and reduce side effects. * **Other Treatments:** Cryotherapy, silicone gel sheeting, and pulsed dye laser (PDL) are other common modalities. * **Surgical Caution:** Simple excision of a keloid has a high recurrence rate (up to 50-100%) unless followed by adjuvant therapy like pressure garments or radiotherapy.

Question 14: Which drug is used for intralesional injection of 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. The underlying medical concept involves its potent anti-inflammatory and immunosuppressive actions. Corticosteroids inhibit fibroblast proliferation, decrease collagen synthesis, and increase the production of collagenase, which helps in flattening the firm, fibrous tissue of a keloid. **Analysis of Options:** * **Triamcinolone (Correct):** It is preferred because it is a **suspension** with low solubility, allowing the drug to remain at the site of injection for a prolonged period (depot effect), providing sustained action within the dense keloid tissue. * **Prednisolone:** While a potent steroid, it is typically used systemically (oral) or topically. It lacks the specific pharmacokinetic profile (insolubility) required for effective intralesional depot therapy in scars. * **Hydrocortisone:** This is a short-acting, low-potency corticosteroid. It is generally too weak to break down the dense collagen bundles found in keloids. * **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:** * **Concentration:** Usually used in concentrations of **10–40 mg/mL**. * **Side Effects:** Local skin atrophy, telangiectasia, and hypopigmentation are common adverse effects of intralesional TAC. * **Combination Therapy:** For resistant keloids, Triamcinolone is often combined with **5-Fluorouracil (5-FU)** or cryotherapy for better efficacy. * **Other uses of Intralesional TAC:** Alopecia areata, lichen planus hypertrophicus (LPH), and cystic acne.

Question 15: What is the recommended treatment for post-radiation skin desquamation?

A. Petroleum jellies
B. Observation alone (Correct Answer)
C. Surgery
D. Antibiotic coverage

Explanation: **Explanation:** Radiation dermatitis is a common side effect of radiotherapy, categorized into stages based on severity. **Dry desquamation** (characterized by erythema, dryness, and scaling) and mild **moist desquamation** (serous exudate and peeling) are typically self-limiting processes. **Why "Observation alone" is correct:** In modern dermatological management of post-radiation skin changes, the primary goal is to maintain a clean environment and allow the skin’s natural regenerative processes to occur. For mild desquamation, conservative management—often termed "observation" or "supportive care"—is the standard. This involves avoiding irritants (harsh soaps, friction) and allowing the basal layer of the epidermis to repopulate. While gentle moisturizers are often used for comfort, the clinical progression itself does not require active medical or surgical intervention. **Analysis of Incorrect Options:** * **A. Petroleum jellies:** While emollients can soothe dry skin, heavy occlusives like petroleum jelly are often avoided immediately before radiation sessions (due to the "bolus effect" which increases surface dose) and are not a "treatment" for the underlying cellular damage. * **C. Surgery:** Surgery is contraindicated in acute radiation desquamation. It is only reserved for late-stage complications like non-healing radiation necrosis or secondary malignancies (e.g., BCC/SCC). * **D. Antibiotic coverage:** Prophylactic antibiotics are not indicated unless there is clear clinical evidence of secondary bacterial infection (impetiginization). **High-Yield Clinical Pearls for NEET-PG:** * **Grading:** Radiation dermatitis is graded by RTOG (Radiation Therapy Oncology Group) or CTCAE scales. * **Management:** For **Dry Desquamation**, use hydrophilic lotions (e.g., Aloe Vera). For **Moist Desquamation**, use hydrocolloid or silver-leaf dressings to promote moist wound healing. * **Late Sequelae:** Chronic radiation dermatitis is characterized by the "triad" of **telangiectasia, atrophy, and fibrosis.**

Question 16: Which of the following is NOT a drug-induced cause of Addison's disease?

A. Skin atrophy
B. Telangiectasia
C. Folliculitis
D. Photosensitivity (Correct Answer)

Explanation: **Explanation:** The question asks for a side effect that is **NOT** typically associated with the prolonged use of topical corticosteroids. While the question mentions "Addison's disease," in the context of dermatology, this refers to the systemic suppression of the Hypothalamic-Pituitary-Adrenal (HPA) axis, but the options provided focus on the **local cutaneous side effects** of topical steroids. **Why Photosensitivity is the Correct Answer:** Photosensitivity is not a recognized side effect of topical corticosteroids. In fact, steroids are often used to *treat* inflammatory photodermatoses (like Polymorphous Light Eruption) due to their potent anti-inflammatory and immunosuppressive properties. **Analysis of Incorrect Options (Local Side Effects of Steroids):** * **Skin Atrophy:** Steroids inhibit keratinocyte proliferation and reduce collagen synthesis by fibroblasts, leading to thinning of the epidermis and dermis. * **Telangiectasia:** Chronic use causes the release of nitric oxide and thinning of the dermal matrix, leading to permanent dilation of superficial capillaries. * **Folliculitis:** Steroids cause local immunosuppression and can induce "Steroid Acne" or "Steroid Folliculitis" (monomorphic pustules without comedones) by altering the local flora and follicular epithelium. **High-Yield Clinical Pearls for NEET-PG:** * **Systemic Side Effects:** Prolonged use of potent topical steroids over large surface areas can cause **Iatrogenic Cushing’s Syndrome** or **HPA axis suppression** (Secondary Adrenal Insufficiency). * **Tachyphylaxis:** This refers to the rapid decrease in response to a drug (tolerance) after repeated doses, common with topical steroids. * **Striae Distensae:** These are permanent linear scars (stretch marks) caused by dermal collagen degradation; they are irreversible even after stopping the drug. * **Classification:** Remember the **Stoughton-Cornell Classification** (7 classes), where Class I (Clobetasol propionate) is the most potent and Class VII (Hydrocortisone) is the least.

Question 17: What is the drug of choice for Type II Lepra Reaction?

A. Thalidomide
B. Steroids (Correct Answer)
C. Clofazamine
D. Rifampicin

Explanation: **Explanation:** **Type II Lepra Reaction (Erythema Nodosum Leprosum - ENL)** is a Type III hypersensitivity reaction (immune-complex mediated) occurring primarily in multibacillary leprosy (BL/LL). It presents with tender subcutaneous nodules, fever, and systemic involvement (neuritis, arthritis, iritis). **Why Steroids are the Correct Answer:** Systemic **Corticosteroids (Prednisolone)** are the first-line drug of choice for Type II reactions because they provide rapid anti-inflammatory and immunosuppressive action. They are essential to prevent permanent nerve damage and manage acute systemic symptoms. While Thalidomide is highly effective, steroids remain the standard initial treatment, especially in cases involving neuritis. **Analysis of Incorrect Options:** * **A. Thalidomide:** It is the drug of choice specifically for **chronic, recurrent, or steroid-dependent** ENL. However, it is contraindicated in women of childbearing age (teratogenic) and acts slower than steroids in acute settings. * **C. Clofazimine:** Used as a steroid-sparing agent in chronic ENL. It has anti-inflammatory properties but takes 4–6 weeks to show effect, making it unsuitable for acute management. * **D. Rifampicin:** This is a bactericidal component of MDT. It has no role in managing the immunological reaction itself; in fact, reactions occur due to the release of antigens from dead bacilli. **High-Yield Clinical Pearls for NEET-PG:** * **Type I Reaction:** Delayed hypersensitivity (Type IV); Drug of Choice: **Steroids**. * **Type II Reaction:** Immune-complex mediated (Type III); Drug of Choice: **Steroids** (Thalidomide for recurrent cases). * **MDT during reactions:** Never stop Multi-Drug Therapy (MDT) during a Lepra reaction. * **Thalidomide side effect:** Phocomelia (seal-like limbs) in the fetus.

Question 18: All of the following are side effects of topical steroids EXCEPT:

A. Skin atrophy
B. Telangiectasia
C. Folliculitis
D. Photosensitivity (Correct Answer)

Explanation: **Explanation:** Topical corticosteroids are among the most frequently prescribed medications in dermatology, but their prolonged or inappropriate use leads to predictable local side effects. **Why Photosensitivity is the Correct Answer:** Photosensitivity is **not** a recognized side effect of topical steroids. In fact, steroids are often used therapeutically to *treat* inflammatory photodermatoses (like Polymorphous Light Eruption) due to their potent anti-inflammatory and immunosuppressive properties. **Analysis of Incorrect Options (Side Effects of Topical Steroids):** * **Skin Atrophy (Option A):** This is the most common side effect. Steroids inhibit keratinocyte proliferation and fibroblast function, leading to thinning of the epidermis and loss of dermal collagen/ground substance. * **Telangiectasia (Option B):** Steroids cause the release of nitric oxide, leading to persistent dilatation of superficial dermal capillaries. This is often seen alongside atrophy, making the vessels more visible. * **Folliculitis (Option C):** Topical steroids can cause "Steroid Acne" or "Steroid Folliculitis." They are also immunosuppressive, which can predispose the hair follicles to secondary bacterial or fungal infections. **High-Yield Clinical Pearls for NEET-PG:** * **Tinea Incognito:** A classic exam favorite where a fungal infection's appearance is modified (less inflamed but more widespread) due to inappropriate steroid use. * **Striae Distensae:** Irreversible "stretch marks" caused by dermal collagen degradation. * **Tachyphylaxis:** A decrease in therapeutic response to a drug after repeated use; common with potent steroids. * **Systemic Absorption:** Can lead to Cushing’s syndrome or HPA axis suppression, especially in infants or when used under occlusion.

Question 19: Which among the following drugs does not commonly produce fixed drug eruptions?

A. Tetracycline
B. Ibuprofen
C. Sulphonamides
D. Mepacrine (Correct Answer)

Explanation: **Explanation:** **Fixed Drug Eruption (FDE)** is a distinctive type of cutaneous drug reaction characterized by recurrent, well-demarcated, erythematous or dusky plaques that appear in the **exact same anatomical location** upon re-exposure to the offending drug. **Why Mepacrine is the correct answer:** Mepacrine (Quinacrine) is an antimalarial and antiprotozoal agent. While it is notorious for causing **yellowish skin discoloration** and **lichenoid drug eruptions**, it is not a common or classic cause of Fixed Drug Eruptions. In the context of NEET-PG, FDE is most strongly associated with specific classes like NSAIDs and antimicrobials. **Analysis of Incorrect Options:** * **Sulphonamides (C):** Historically the **most common cause** of FDEs worldwide. They frequently cause lesions on the genitalia. * **Tetracyclines (A):** A very common cause of FDEs, often presenting with lesions on the glans penis. * **Ibuprofen (B):** NSAIDs (including Ibuprofen, Naproxen, and Oxyphenbutazone) are leading causes of FDEs. NSAID-induced FDEs often present as multiple or generalized lesions. **High-Yield Clinical Pearls for NEET-PG:** 1. **Most Common Site:** The glans penis is the most common site for FDEs in males. 2. **Commonest Culprits (The "S-N-A-T" Mnemonic):** **S**ulphonamides, **N**SAIDs, **A**nticonvulsants, and **T**etracyclines. 3. **Pathogenesis:** Mediated by **effector memory CD8+ T cells** that remain resident in the skin even after the lesion heals. 4. **Clinical Feature:** Lesions often heal with significant **post-inflammatory hyperpigmentation**. 5. **Bullous FDE:** A severe variant that must be differentiated from Stevens-Johnson Syndrome (SJS).

Question 20: Imiquimod is used for the treatment of which of the following conditions?

A. Molluscum contagiosum
B. Warts
C. Skin cancer
D. All of the above (Correct Answer)

Explanation: **Explanation:** Imiquimod is a potent **topical immune response modifier**. Its primary mechanism of action involves acting as an agonist for **Toll-like receptor 7 (TLR-7)**. This stimulation induces the release of pro-inflammatory cytokines, most notably **Interferon-alpha (IFN-α)**, Interleukin-6 (IL-6), and Tumor Necrosis Factor-alpha (TNF-α). These cytokines activate the innate and cell-mediated immune systems to target both viral-infected cells and tumor cells. **Why "All of the Above" is correct:** * **Warts (Option B):** Imiquimod is FDA-approved for **Anogenital warts** (Condyloma acuminata) caused by HPV. It enhances the body's ability to clear the viral load. * **Skin Cancer (Option C):** It is used for treating **Superficial Basal Cell Carcinoma (sBCC)** and **Actinic Keratosis** (a pre-malignant precursor to Squamous Cell Carcinoma). Its pro-apoptotic and anti-tumor effects make it an excellent non-invasive option for low-risk lesions. * **Molluscum Contagiosum (Option A):** While often used off-label, it is a clinically recognized treatment for Molluscum, especially in extensive or recalcitrant cases, by stimulating an immune response against the Poxvirus. **Clinical Pearls for NEET-PG:** * **Mechanism:** TLR-7 agonist $\rightarrow$ IFN-α induction. * **Common Side Effects:** Local skin reactions (erythema, itching, burning, and erosion) are expected and indicate the drug is working. * **Other Indications:** It is also used off-label for Keloids (post-excision), Bowens’s disease, and Lentigo maligna. * **Contraindication:** It should be used with caution in patients with pre-existing autoimmune conditions.

Practice by Chapter

Topical Corticosteroids

Practice Questions

Topical Antibiotics

Practice Questions

Topical Antifungals

Practice Questions

Topical Antivirals

Practice Questions

Topical Retinoids

Practice Questions

Systemic Retinoids

Practice Questions

Immunosuppressive Agents

Practice Questions

Antihistamines in Dermatology

Practice Questions

Biological Agents in Dermatology

Practice Questions

Dermatological Vehicles and Delivery Systems

Practice Questions

Phototherapeutic Agents

Practice Questions

Adverse Cutaneous Drug Reactions

Practice Questions

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