Drugs Used in Skin Disorders Practice Questions

Q: Apremilast is:

A PDE 4 inhibitor. **Explanation:** **Apremilast** is an oral small-molecule inhibitor of **Phosphodiesterase 4 (PDE4)**. In inflammatory cells, PDE4 is the dominant enzyme responsible for the degradation of cyclic adenosine monophosphate (cAMP). By inhibiting PDE4, Apremilast increases intracellular cAMP levels, which in turn downregulates the inflammatory response by modulating the expression of pro-inflammatory cytokines (like TNF-α, IL-23, and IFN-γ) and increasing anti-inflammatory cytokines (like IL-10). **Analysis of Options:** * **Option B (Correct):** Apremilast specifically targets PDE4. It is FDA-approved for the treatment of **moderate-to-severe plaque psoriasis** and **psoriatic arthritis**. * **Option A:** PDE3 inhibitors (e.g., **Milrinone**, Amrinone) are primarily used as inotropes in acute heart failure to increase cardiac contractility and cause vasodilation. * **Option C:** PDE5 inhibitors (e.g., **Sildenafil**, Tadalafil) are used for erectile dysfunction and pulmonary arterial hypertension by increasing cGMP levels. * **Option D:** PDE6 is found in the retina. Inhibition of PDE6 (often a side effect of PDE5 inhibitors) leads to visual disturbances, such as the "blue-tint" vision (cyanopsia). **High-Yield Clinical Pearls for NEET-PG:** * **Route:** Administered **orally**, making it a preferred alternative to biologicals for patients who prefer to avoid injections. * **Side Effects:** The most common side effects are **diarrhea, nausea**, and upper respiratory tract infections. A significant psychiatric side effect to remember is **depression and weight loss**. * **Indications:** Plaque psoriasis, Psoriatic arthritis, and **Behçet’s disease** (for oral ulcers). * **Mechanism Mnemonic:** Apremilast = **4**premilast (PDE**4**).

Q: Which of the following statements is NOT true regarding silver sulfadiazine used in the management of burns?

It is primarily used for treating established infections.. **Explanation:** Silver sulfadiazine is a topical sulfonamide widely used in burn management. The correct answer is **Option B** because silver sulfadiazine is primarily used for the **prophylaxis (prevention)** of infection in burn wounds, rather than the treatment of deep-seated, established infections. It has limited eschar penetration, making it less effective once an infection has become deep or systemic. **Analysis of Options:** * **Option A (Incorrect):** Local side effects like burning, itching, and rashes are common adverse reactions to topical application. * **Option C (Incorrect):** Beyond burns, it is clinically indicated for preventing infections in chronic pressure sores and leg ulcers. * **Option D (Incorrect):** The mechanism involves the slow release of silver ions, which are toxic to bacteria (bactericidal) by damaging the cell wall and DNA. The sulfadiazine component also provides additional antimicrobial activity. **High-Yield Clinical Pearls for NEET-PG:** * **Spectrum:** It is effective against a broad range of organisms, including *Pseudomonas aeruginosa* and *Candida albicans*. * **Adverse Effects:** A unique systemic side effect is **transient leukopenia** (usually occurs 2-3 days after starting therapy). * **Contraindications:** Avoid in pregnancy (near term), premature infants, and neonates due to the risk of **kernicterus** (sulfonamides displace bilirubin from albumin). * **Mafenide Acetate:** Unlike silver sulfadiazine, Mafenide acetate penetrates thick eschar well but can cause **metabolic acidosis** (via carbonic anhydrase inhibition).

Q: Permethrin is used in the treatment of which condition?

Scabies. **Explanation:** **Permethrin** is a synthetic pyrethroid [1] and is currently considered the **drug of choice (DOC) for Scabies** (caused by *Sarcoptes scabiei*) [2]. It acts by disrupting the sodium channel current in the neuronal membranes of the parasites, leading to delayed repolarization, paralysis, and death of the mite [1]. For scabies, it is applied as a 5% cream over the entire body (neck down) and left for 8–12 hours before washing [1], [2]. **Analysis of Incorrect Options:** * **B. Leprosy:** This is a chronic infectious disease caused by *Mycobacterium leprae*. It is treated with **Multidrug Therapy (MDT)** consisting of Rifampicin, Dapsone, and Clofazimine. * **C. Body Louse:** While Permethrin 1% is used for Head Lice (*Pediculus humanus capitis*) [1], the primary treatment for Body Lice involves **decontamination of clothing and bedding** (where the lice live), as they only move to the skin to feed. * **D. Leishmaniasis:** This protozoal infection (Kala-azar) is treated with drugs like **Liposomal Amphotericin B** (DOC), Miltefosine, or Paromomycin. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** Permethrin 5% is the DOC for Scabies; Permethrin 1% is the DOC for Head Lice [1], [2]. * **Safety Profile:** It is preferred over Lindane because it is less toxic and safe for use in infants (>2 months) and pregnant women [1]. * **Oral Alternative:** **Ivermectin** (200 μg/kg) is an effective oral alternative for scabies, especially in institutional outbreaks or crusted (Norwegian) scabies. * **Mechanism:** It targets the **voltage-gated sodium channels**, similar to the mechanism of DDT [1].

Q: Which of the following is the most potent topical corticosteroid?

Clobetasol. **Explanation:** The potency of topical corticosteroids is determined by their ability to cause vasoconstriction and suppress inflammation. According to the standard **Stoughton-Cornell classification**, topical steroids are divided into seven groups, ranging from Group I (Ultra-high potency) to Group VII (Low potency). **Why Clobetasol is correct:** **Clobetasol propionate (0.05%)** belongs to **Group I (Ultra-high potency)**. It is the most potent topical corticosteroid available. It is typically reserved for severe, resistant dermatoses (like recalcitrant psoriasis or lichen planus) and should not be used on the face, groin, or axilla due to the high risk of skin atrophy and systemic absorption. **Analysis of Incorrect Options:** * **A. Clobetasone:** Often confused with Clobetasol, Clobetasone butyrate is a **moderate-potency** (Group IV/V) steroid. It is much safer for use in milder conditions or sensitive areas. * **C. Betamethasone:** While certain formulations (like Betamethasone dipropionate in optimized vehicles) are high potency, Clobetasol remains superior in vasoconstrictor assays. * **D. Beclomethasone:** This is a **lower to mid-potency** steroid commonly used in inhalers for asthma or as a cream for mild inflammatory skin conditions. **High-Yield NEET-PG Pearls:** 1. **Potency Ranking:** Clobetasol > Halobetasol > Betamethasone dipropionate > Mometasone > Hydrocortisone. 2. **Least Potent:** **Hydrocortisone (1%)** is the least potent (Group VII), making it the safest for pediatric use and facial application. 3. **Side Effects:** Chronic use of high-potency steroids leads to **tachyphylaxis** (diminishing response), skin atrophy, striae, and potential HPA-axis suppression. 4. **Absorption:** Absorption is highest in areas with thin stratum corneum (Scrotum > Face > Axilla > Scalp > Trunk > Palms/Soles).

Q: Isotretinoin is:

Safe in pregnancy. **Explanation:** Isotretinoin (13-cis-retinoic acid) is a systemic retinoid and a first-generation **Vitamin A analogue**. It is the most effective treatment for severe, recalcitrant **nodulocystic acne** because it addresses all four pathogenic factors: sebum production, follicular hyperkeratosis, *C. acnes* colonization, and inflammation. **Analysis of Options:** * **A & B (Incorrect in the context of the "Correct" label):** While Isotretinoin *is* a Vitamin A analogue and *is* used in cystic acne, these are true statements. In many MCQ formats, if a single "correct" answer is pre-marked (as in this prompt), it usually indicates a test of specific contraindications or properties. However, **Option C is medically incorrect**—Isotretinoin is highly **teratogenic**. * **C (The marked answer):** This is a **distractor or an error in the provided key.** Isotretinoin is strictly contraindicated in pregnancy (FDA Category X). It causes "Retinoid Embryopathy" (craniofacial, cardiac, and CNS defects). * **D (Incorrect):** While some retinoids (like Acitretin) are used for psoriasis, Isotretinoin is primarily indicated for acne. **Clinical Pearls for NEET-PG:** 1. **Teratogenicity:** Female patients must follow the **iPLEDGE program**, requiring two forms of contraception and two negative pregnancy tests before starting therapy. Contraception must continue for 1 month after stopping. 2. **Adverse Effects:** Most common is **Cheilitis** (dry lips). High-yield systemic effects include **hypertriglyceridemia**, hepatotoxicity, and psychiatric symptoms (depression/suicidal ideation). 3. **Monitoring:** Baseline and periodic monitoring of Liver Function Tests (LFTs) and Lipid profiles are mandatory. *Note: In a standard exam, Options A and B are scientifically true, while C is a dangerous medical fallacy. Always prioritize "Teratogenicity" as the most important clinical fact regarding Isotretinoin.*

Question 1

Apremilast is:

Accepted Answer

A PDE 4 inhibitor

Answer

A PDE 3 inhibitor

Answer

A PDE 5 inhibitor

Answer

A PDE 6 inhibitor

Question 2

Which of the following statements is NOT true regarding silver sulfadiazine used in the management of burns?

Accepted Answer

It is primarily used for treating established infections.

Answer

Local side effects include burning and itching.

Answer

It is effective in preventing infection of chronic ulcers.

Answer

The released silver ion is responsible for its antibacterial activity.

Question 3

Permethrin is used in the treatment of which condition?

Accepted Answer

Scabies

Answer

Leprosy

Answer

Body Louse

Answer

Leishmaniasis

Question 4

Which of the following is the most potent topical corticosteroid?

Accepted Answer

Clobetasol

Answer

Clobetasone

Answer

Betamethasone

Answer

Beclomethasone

Question 5

Isotretinoin is:

Accepted Answer

Safe in pregnancy

Answer

A vitamin A analogue

Answer

Used in cystic acne

Answer

Used in psoriasis

Drugs Used in Skin Disorders — MCQs

Drugs Used in Skin Disorders — MCQs

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