Dermatology Pharmacology MSK II Fall 2024

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Questions and Answers

What is the predominant organism responsible for cellulitis in outpatient settings?

E. coli

MRSA

MSSA

β-hemolytic streptococcus spp. (correct)

Which of the following is true about the first line treatment for cellulitis?

Penicillin VK is an effective option for treating Strep. spp. (correct)

Doxycycline is the primary treatment option.

Amoxicillin/clavulanic acid targets exclusively MRSA.

Cephalexin does not inhibit cell wall synthesis.

What mechanism of action do beta-lactams like Penicillin VK use?

Inhibits DNA replication

Disrupts metabolic pathways

Inhibits cell wall synthesis via peptidoglycan (correct)

Inhibits protein synthesis

In patients with moderate cellulitis, what is the typical recommendation for treatment?

Inpatient admission for IV antibiotics is often necessary. Signup and view all the answers

Why is MRSA coverage usually unnecessary in the general population when treating cellulitis?

MRSA is not common in cellulitis cases. Signup and view all the answers

What is a notable side effect of topical treatments?

Localized burning Signup and view all the answers

Which medication is indicated for use in cases of both pyrantel pamoate allergy and vice versa?

Ivermectin Signup and view all the answers

Which is NOT a side effect associated with Atovaquone?

CNS effects Signup and view all the answers

What is the mechanism of action for Praziquantel?

Disrupts ion transport by increasing cell membrane permeability Signup and view all the answers

In which condition should Praziquantel be avoided?

Ocular cysticercosis Signup and view all the answers

What type of infection is cellulitis classified as?

Bacterial infection Signup and view all the answers

Which of the following conditions is NOT classified under fungal infections?

Erysipelas Signup and view all the answers

Which adverse effect is most commonly associated with the treatment of dermatologic infections?

Gastrointestinal upset Signup and view all the answers

Varicella belongs to which category of dermatologic infections?

Viral infections Signup and view all the answers

What characterizes acute bacterial skin and skin structure infections (ABSSSI)?

Includes both nonpurulent and purulent wound infections Signup and view all the answers

Which of the following represents a notable interaction with dermatologic medications?

Increased risk of hyperglycemia with steroid use Signup and view all the answers

Which of the following infections is caused by a viral agent?

Herpes simplex Signup and view all the answers

What is a primary consideration when selecting treatment for bacterial skin infections?

Known drug allergies Signup and view all the answers

Which of the following conditions is primarily associated with the treatment of endoparasitic infections?

Babesiosis Signup and view all the answers

Which of the following best describes the mechanism of action for antifungal medications?

Disrupting cell membrane integrity Signup and view all the answers

What is the mechanism of action of Sulfamethoxazole/trimethoprim?

Inhibits dihydrofolate reductase Signup and view all the answers

Which of the following is a potential adverse effect of linezolid when used for a prolonged duration?

Myelosuppression Signup and view all the answers

What should be monitored when prescribing Sulfamethoxazole/trimethoprim to a patient on warfarin?

PT/INR levels Signup and view all the answers

In which circumstance is clindamycin indicated for use?

Limited Streptococcus spp. coverage Signup and view all the answers

What condition must be considered when prescribing linezolid due to potential drug interactions?

Serotonin syndrome Signup and view all the answers

Which antibiotic is recommended for treating severe purulent skin infections?

Daptomycin Signup and view all the answers

How should clindamycin be used cautiously?

In patients with a history of C.diff infections Signup and view all the answers

Which of the following organisms can be treated with clindamycin?

MSSA Signup and view all the answers

What is the primary mechanism of action for Permethrin and pyrethrins in treating lice?

Disrupting sodium transport across neuronal membranes Signup and view all the answers

Which treatment for lice is contraindicated in patients with a Chrysanthemum allergy?

Pyrethrins Signup and view all the answers

How does Spinosad cause its neurotoxic effects?

By causing neuronal hyperexcitation through acetylcholine receptors Signup and view all the answers

What measure should be taken after treating a lice infestation?

Treating bedding and clothing is important Signup and view all the answers

What is the treatment of choice for scabies?

Topical Permethrin or Topical Spinosad or Oral Ivermectin Signup and view all the answers

What should be done regarding nits after lice treatment?

They must be combed out thoroughly Signup and view all the answers

Which of the following is NOT a feature of topical Permethrin treatment?

Has no side effects Signup and view all the answers

What is the role of Piperonyl butoxide in lice treatment?

It enhances the action of permethrin Signup and view all the answers

Study Notes

Learning Objectives

Describe medications for skin disorders: mechanism of action, key adverse effects, contraindications, and notable drug-drug interactions.
Formulate a treatment plan based on patient case scenarios.

Dermatologic Infections

Categories of Infections: Bacterial, Fungal, Viral.
Bacterial Infections Include:
- Cellulitis
- Furuncle/Carbuncle
- Erysipelas
- Impetigo
- Leprosy
- Cutaneous Anthrax
Fungal Infections Include:
- Tinea group
- Candidiasis
- Histoplasmosis
- Blastomycosis
- Paracoccidioidomycosis
- Sporotrichosis
- Coccidioidomycosis
Viral Infections Include:
- Herpes simplex
- Varicella
- Endoparasitic infections such as babesiosis and schistosomiasis.

Cellulitis

Predominant Organism: β-hemolytic streptococcus spp. (Strep pyogenes) (57-75%).
First-Line Treatment: Oral Beta-lactams (Penicillin VK, Amoxicillin/clavulanic acid, Cephalexin).
Mechanism of Action for Beta-lactams: Inhibit cell wall synthesis via peptidoglycan.
Alternatives:
- Dicloxacillin: Covers Strep spp., MSSA.
- Doxycycline: Covers Strep spp., MSSA, limited MRSA (inhibits 30S ribosomal subunit).
MRSA Coverage: Generally unnecessary in the general population; moderate cases may require inpatient IV antibiotics.

Drug Options for Cellulitis

Sulfamethoxazole/trimethoprim (SMX-TMP): Inhibits dihydrofolate reductase; be cautious with sulfa allergies.
Clindamycin: Limited coverage for Strep spp.; can cause C. difficile infections.
Linezolid: Inhibits protein synthesis (50S ribosomal subunit); risk of serotonin syndrome with MAOIs.

Severe Cellulitis Treatment

Severe/Inpatient Management: Vancomycin, Daptomycin, Linezolid, Ceftaroline.

Endoparasitic Infections

Atovaquone: Selectively inhibits mitochondrial electron transport; may cause GI disturbances.
Praziquantel: Disrupts ion transport; avoid in ocular cysticercosis and during pregnancy.

Treatment for Ectoparasites

Lice Treatment:
- Preferred: Topical Permethrin 1% or Pyrethrins, Spinosad (causes neurotoxicity).
- Mechanism: Disrupts sodium transport in neuronal membranes leading to paralysis.
- Precautions: Contraindicated in Chrysanthemum allergies; treat bedding and clothing.
Scabies Treatment:
- First-Line: Topical Permethrin or Spinosad, Oral Ivermectin.
- Mechanism: Disrupts sodium transport across neuronal membranes, causing neurotoxicity and paralysis.

Key Pearls

For lice and scabies, proper combing and environmental disinfection are crucial.
Repeat treatments for lice after 7 days; handle potential skin irritation from topical agents.

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Description

Test your knowledge on pharmacology related to dermatology in the MSK II course for Fall 2024. This quiz covers mechanisms of action, adverse effects, contraindications, and drug interactions for medications used in treating skin disorders. Additionally, you will formulate treatment plans based on patient scenarios.