MSK II Fall 2024 Derm Pharmacology Lecture Notes PDF

Derm Pharmacology MSK II – Fall 2024 Kelly Rudd, PharmD LEARNING OBJECTIVES 1. For each of the medications used to treat skin disorders: Describe the mechanism of action Key adverse effects Contraindications Notable drug-drug intera...

Derm Pharmacology MSK II – Fall 2024 Kelly Rudd, PharmD LEARNING OBJECTIVES 1. For each of the medications used to treat skin disorders: Describe the mechanism of action Key adverse effects Contraindications Notable drug-drug interactions 2. Given a patient case scenario, be able to formulate a treatment plan which includes but is not limited to appropriate indication, medication treatment, and applicable factors from Objective 1.  Dermatologic Infections (“Other Dermatoses” to follow) Bacterial infections Fungal infections Viral infections Cellulitis Tinea group Herpes simplex Furuncle/Carbuncle Candidiasis Varicella Erysipelas Histoplasmosis Impetigo Blastomycosis Endoparasitic infections Leprosy Paracoccidioidomycosis American Trypanosomiasis Cutaneous Anthrax Sporotrichosis Babesiosis Coccidioidomycosis Hookworms & Threadworms Schistosomiasis Lice Scabies  Dermatologic Infections Bacterial infections Fungal infections Viral infections Cellulitis Tinea group Herpes simplex Erysipelas Candidiasis Varicella Folliculitis/Furuncle/Carbuncle Histoplasmosis Impetigo Blastomycosis Endoparasitic infections Leprosy Paracoccidioidomycosis American Trypanosomiasis Cutaneous Anthrax Sporotrichosis Babesiosis Coccidioidomycosis Hookworms & Threadworms Schistosomiasis Lice Scabies Sanford Guide: Antibacterial Agents: Spectra of Activity (openathens.net)  Dermatologic Infections Bacterial infections Fungal infections Viral infections Cellulitis Tinea group Herpes simplex Erysipelas Candidiasis Varicella Folliculitis/Furuncle/Carbuncle Histoplasmosis Impetigo Blastomycosis Endoparasitic infections Leprosy Paracoccidioidomycosis American Trypanosomiasis Cutaneous Anthrax Sporotrichosis Babesiosis Coccidioidomycosis Hookworms & Threadworms Schistosomiasis Lice Scabies  ABSSSI Acute bacterial skin and skin structure infections Encompasses wound infections that are : nonpurulent (cellulitis, erysipelas) -and- purulent (major cutaneous abscesses) Stevens DL, et al. CID 2014;59(2):e10-52. Antimicrobials (this should not be new) Cellulitis Outpatient: The predominant organism is β-hemolytic streptococcus spp. (Strep. pyogenes) = 57-75% Agent Antimicrobial Spectrum Pearls First Line: Oral Beta-lactams Penicillin VK or Strep. spp, MSSA MOA: Inhibits cell wall synthesis via Amoxicillin/clavulanic acid or peptidoglycan Cephalexin (or cephalosporin) Alternatives Dicloxacillin Strep. spp, MSSA MOA: Inhibits cell wall synthesis or Doxycycline Strep. spp, MSSA, limited MRSA MOA: Inhibits 30S ribosomal subunit GI irritant, causes photosensitivity Avoid in pregnancy, if possible MRSA coverage is usually unnecessary in the general population. Moderate disease often requires inpatient admission for IV antibiotics, and similar meds as to those above. Above assuming the patient is not a diabetic. Sanford Guide: Cellulitis, Erysipelas: Extremities (openathens.net) infxn = infection, PCN = penicillin, MSSA = methicillin-sensitive S. aureus, MRSA = methicillin-resistant S. aureus Periorbital Cellulitis Is a big deal – organisms include gram-positive, gram-negative, and anaerobes Agent Pearls Primary Regimen: Vancomycin MOA: Inhibits cell wall synthesis via D-ala-D-ala PLUS one of the following: (Ceftriaxone and Metronidazole) MOA ceftriaxone: Inhibits cell wall synthesis (peptidoglycan) MOA metronidazole: induces DNA damage via free-radicals Piperacillin-tazobactam MOA: Inhibits cell wall synthesis via peptidoglycan Ampicillin-sulbactam Tazobactam & sulbactam are the beta-lactamase inhibitors Sanford Guide: Orbital cellulitis, periorbital cellulitis (openathens.net)  Erysipelas vs. Cellulitis Erysipelas is a superficial infection (affecting the dermis and superficial lymph vessels), while cellulitis affects the deeper tissues (deep dermis layers and subcutaneous fat). Erysipelas and cellulitis | MSF Medical Guidelines Erysipelas The predominant organism is Group A Strep (S. pyogenes) – assuming non-diabetic Agent MOA Pearls Oral Agents (choose one agent) Penicillin VK or MOA: Inhibits cell wall synthesis via Like Cellulitis Amoxicillin/clavulanic acid or peptidoglycan Cephalexin (or cephalosporin) Clindamycin MOA: Inhibits 50S ribosomal subunit alternatives Erythromycin Increased GI irritation P450 Inhibitor Intravenous (choose one agent) Procaine Penicillin G MOA: inhibits cell wall synthesis via *different formulations for IV and IM Cefazolin or Ceftriaxone peptidoglycan Caution with PCN allergy* Azithromycin MOA: Inhibits 50S ribosomal subunit Or potentially clindamycin Consider for severe penicillin allergy *There is about a 10% cross-sensitivity between PCN and Cephalosporins. Avoid Cephalosporins if serious (anaphylactic) reaction to PCN. Sanford Guide: Cellulitis, Erysipelas: Extremities (openathens.net) Abscesses: furuncles, carbuncles, etc. The predominant organism is MRSA/MSSA up to 75% - often requires I&D plus antimicrobial therapy Agent Antimicrobial Spectrum Pearls First Line (chose one agent) Dicloxacillin Strep. spp, MSSA *Only if Low suspicion of MRSA* Sulfamethoxazole/trimethoprim MOA: Inhibits dihydrofolate reductase (SMX-TMP) Drug interaction with warfarin *Watch Sulfa allergy MSSA + MRSA Caution in pregnancy (maybe OK in 2nd/3rd trimester) Clindamycin Limited Strep. spp coverage MOA: Inhibits 50S ribosomal subunit GI irritant, C. difficile infections Alternatives (chose one agent) Clindamycin Strep. spp, MSSA, limited MRSA See previous Linezolid Strep. spp, MSSA, MRSA MOA: Inhibits 50S ribosomal subunit (at the * Placeholder: has monoamine-oxidase inhibitor 23S ribosomal RNA – not a macrolide) (MAOI) and selective serotonin-reuptake inhibitor (SSRI) Myelosuppression after 2 weeks of therapy drug interactions & can cause serotonin syndrome! Neuropathy after 4 weeks of therapy Sanford Guide: Skin Abscess, Boils, Furuncles (openathens.net)  Cellulitis & Abscesses: Severe disease (inpatient) Purulent, Vancomycin or Daptomycin Severe: or Linezolid or Ceftaroline. Non-purulent, Vancomycin AND Severe or Sepsis: piperacillin/tazobactam If concern for (Carbapenem or Pip/tazo) + necrotizing infection: (MRSA) + (Clindamcyin) Stevens DL, et al. CID 2014;59(2):e10-52. Pic: iStock Impetigo The predominant organisms are Group A Strep (S. pyogenes) and Staph. aureus Agent MOA Pearls First-line is Topical Therapy: Mupirocin Ointment MOA: inhibits isoleucyl-transfer RNA Effective against MRSA (halting protein & RNA synthesis) If oral antibiotics are required (choose one agent): Penicillin VK or dicloxacillin MOA: inhibits cell wall synthesis via First line oral antibiotic Cephalexin peptidoglycan Option if penicillin allergy SMX-TMP If allergy to penicillins & cephalosporins. See previous for MOAs. Clindamycin SMX-TMP: sulfamethoxazole-trimethoprim Sanford Guide: Impetigo (openathens.net)  Leprosy The predominant organism is Mycobacterium leprae Agent MOA Pearls Combination therapy is recommended Rifampin MOA: inhibits DNA-dependent RNA polymerase Potent P450 Enzyme inducer (Ramps up) (inhibiting RNA synthesis) Red-orange secretions Pulmonary- & hepato-toxic and Dapsone MOA: antagonist of para-aminobenzoic acid and Causes blood dyscrasias prevents use of PABA for synthesis of folic acid Check for G6PD deficiency (risk for hemolytic anemia) The two above with or without Clofazimine MOA: unknown?!?! Only available in the US via “expanded access programs” via an FDA investigational drug protocol Sanford Guide: Mycobacterium leprae, Leprosy (openathens.net) Cutaneous Anthrax The predominant organism is Bacillus anthracis Agent MOA Pearls No evidence of systemic disease (choose one agent) Ciprofloxacin MOA: Inhibits DNA gyrase For ages 1 month to adult (including pregnant) Doxycycline MOA: Inhibits 30S ribosomal subunit For newborns < 1 month of age Alternatives (choose one agent) Other Quinlones See above Ages 1 month to adult (NON-PREGNANT) Clindamycin MOA: Inhibits 50S ribosomal subunit Pen VK or MOA: Inhibits cell wall synthesis via ONLY if you know the strain is susceptible Amoxicillin peptidoglycan Sanford Guide: Anthrax, Cutaneous (openathens.net)  Dermatologic Infections Bacterial infections Fungal infections Viral infections Cellulitis Tinea group Herpes simplex Erysipelas Candidiasis Varicella Folliculitis/Furuncle/Carbuncle Histoplasmosis Impetigo Blastomycosis Endoparasitic infections Leprosy Paracoccidioidomycosis American Trypanosomiasis Cutaneous Anthrax Sporotrichosis Babesiosis Coccidioidomycosis Hookworms & Threadworms Schistosomiasis Lice Scabies  Antifungal Therapies β-glucan Diarrhea Flushing (histamine) Liver Toxicity Binds ergosterol = leaky pores ↓DNA/RNA Renal Toxicity P450 Anemia synthesis by conversion to Arrhythmias 5-FU Hypotension Liver Toxicity & P450 Inhibition* Myelosuppression *Notable P450 interactions: theophylline, warfarin, amiodarone/flecainide, antidepressants (TCAs & SSRIs) Antifungal Pharmacology Fluconazole, itraconazole, clotrimazole, & friends (Azoles): Inhibits ergosterol synthesis (by inhibiting the P450 enzyme that converts lanosterol to ergosterol.) POTENT P450 inhibitor. Can cause hepatotoxicity (monitor LFTs) and QT prolongation. Caspofungin & Micafungin: Echinocandins that inhibit fungal cell wall synthesis via B-glucan inhibition. Can cause GI upset (diarrhea) and flushing. Amphotericin B (aka Ampho-terrible, a Polyene): Binds ergosterol, forming membrane pores and electrolyte leakage. Causes hypotension, arrhythmias, anemia, IV phlebitis, fever/chills, & SERIOUS nephrotoxicity. Antifungal Pharmacology Fluconazole, itraconazole, clotrimazole, & friends (Azoles): Inhibits ergosterol synthesis (by inhibiting the P450 enzyme that converts lanosterol to ergosterol.) POTENT P450 inhibitor. Can cause hepatotoxicity (monitor LFTs) and QT prolongation. Caspofungin & Micafungin: Echinocandins that inhibit fungal cell wall synthesis via B-glucan inhibition. Can cause GI upset (diarrhea) and flushing. Amphotericin B (aka Ampho-terrible, a Polyene): Binds ergosterol, forming membrane pores and electrolyte leakage. Causes hypotension, arrhythmias, anemia, IV phlebitis, fever/chills, & SERIOUS nephrotoxicity. NEW Terbinafine & Tolnaftate: An allylamine antifungal that inhibits squalene epoxidase (also known as squalene monooxygenase) to prevent the formation of ergosterol. Can cause liver toxicity if taken orally. Flucytosine: An antimetabolite which is metabolized in the fungal cell to 5-fluorouracil (5-FU), which inhibits nucleic acid synthesis. Can cause myelosuppression. Nystatin: A polyene, like amphotericin, but only used topically. Few side effects (rarely hypersensitivity, SJS) Antifungal Pharmacology Fluconazole, itraconazole, clotrimazole, & friends (Azoles): Inhibits ergosterol synthesis (by inhibiting the P450 enzyme that converts lanosterol to ergosterol.) POTENT P450 inhibitor. Can cause hepatotoxicity (monitor LFTs) and QT prolongation. Caspofungin & Micafungin: Echinocandins that inhibit fungal cell wall synthesis via B-glucan inhibition. Can cause GI upset (diarrhea) and flushing. Amphotericin B (aka Ampho-terrible, a Polyene): Binds ergosterol, forming membrane pores and electrolyte leakage. Causes hypotension, arrhythmias, anemia, IV phlebitis, fever/chills, & SERIOUS nephrotoxicity. Terbinafine & Tolnaftate: An allylamine antifungal that inhibits squalene epoxidase (also known as squalene monooxygenase) to prevent the formation of ergosterol. Can cause liver toxicity if taken orally. Flucytosine: An antimetabolite which is metabolized in the fungal cell to 5-fluorouracil (5-FU), which inhibits nucleic acid synthesis. Can cause myelosuppression. Nystatin: A polyene, like amphotericin, but only used topically. Few side effects (rarely hypersensitivity, SJS) Fungal Infections Infection Treatment of Choice Tinea Topical azoles or topical tolnaftate (superficial epidermal infections) -or- dermatophytes Oral azoles or oral terbinafine (deeper infections: follicles, dermis, nails) *Nystatin is NOT effective. Avoid concurrent topical steroids. Candidiasis Skin: nystatin, clotrimazole topical, oral fluconazole if severe Vaginal: oral fluconazole or topical azole Oral or esophageal: nystatin S&S, clotrimazole troche, or oral fluconazole Systemic: fluconazole, echinocandins, or amphotericin B Histoplasmosis Itraconazole (limited disease) Blastomycosis Amphotericin B (severe disease) Coccidioidomycosis Sporotrichosis Paracoccidioidomycosis Itraconazole (limited disease) Amphotericin B (severe disease) If CNS Involvement: SMX/TMP or Amphotericin B Tinea infections of various locations that metabolize and subsist upon keratin in the skin, hair, and nails. Tinea corporis – infection of body surfaces (”ringworm”) Tinea pedis – feet/soles (“athlete’s foot”) Tinea cruris – groin, inner thighs, buttocks (“jock itch”) Tinea faciei – face Tinea manuum – hand/palm Tinea capitis – scalp hair and head Tinea barbae – beard hair Causative organisms: Trichophyton, Microsporum, Epidermophyton Fungal Infections Infection Treatment of Choice Tinea Topical azoles or topical tolnaftate (superficial epidermal infections) -or- dermatophytes Oral azoles or oral terbinafine (deeper infections: follicles, dermis, nails) *Nystatin is NOT effective. Avoid concurrent topical steroids. Candidiasis Skin: nystatin, clotrimazole topical, oral fluconazole if severe Vaginal: oral fluconazole or topical azole Oral or esophageal: nystatin S&S, clotrimazole troche, or oral fluconazole Systemic: fluconazole, echinocandins, or amphotericin B Histoplasmosis Itraconazole (limited disease) Blastomycosis Amphotericin B (severe disease) Coccidioidomycosis Sporotrichosis Paracoccidioidomycosis Itraconazole (limited disease) Amphotericin B (severe disease) If CNS Involvement: SMX/TMP or Amphotericin B Fungal Infections Infection Treatment of Choice Tinea Topical azoles or topical tolnaftate (superficial epidermal infections) -or- dermatophytes Oral azoles or oral terbinafine (deeper infections: follicles, dermis, nails) *Nystatin is NOT effective. Avoid concurrent topical steroids. Candidiasis Skin: nystatin or clotrimazole topical or oral fluconazole if severe Vaginal: oral fluconazole or topical azole Oral or esophageal: nystatin S&S or clotrimazole troche* or oral fluconazole Systemic: fluconazole, echinocandins, or amphotericin B Histoplasmosis Itraconazole (limited disease) Blastomycosis Amphotericin B (severe disease) Coccidioidomycosis Sporotrichosis Paracoccidioidomycosis Itraconazole (limited disease) Amphotericin B (severe disease) If CNS Involvement: SMX/TMP or Amphotericin B *A troche is similar to a lozenge, S&S = swish and spit. Fungal Infections Infection Treatment of Choice Tinea Topical azoles or topical tolnaftate (superficial epidermal infections) dermatophytes Oral azoles or oral terbinafine (deeper infections: follicles, dermis, nails) *Nystatin is NOT effective. Avoid concurrent topical steroids. Candidiasis Skin: nystatin, clotrimazole topical, oral fluconazole if severe Vaginal: oral fluconazole or topical azole Oral or esophageal: nystatin S&S, clotrimazole troche, or oral fluconazole Systemic: fluconazole, echinocandins, or amphotericin B Histoplasmosis Itraconazole (limited disease) -or- Blastomycosis Amphotericin B (severe disease) Coccidioidomycosis Sporotrichosis Paracoccidioidomycosis Itraconazole (limited disease) Amphotericin B (severe disease) If CNS Involvement: SMX/TMP or Amphotericin B Fungal Infections Infection Treatment of Choice Tinea Topical azoles or topical tolnaftate (superficial epidermal infections) -or- dermatophytes Oral azoles or oral terbinafine (deeper infections: follicles, dermis, nails) *Nystatin is NOT effective. Avoid concurrent topical steroids. Candidiasis Skin: nystatin, clotrimazole topical, oral fluconazole if severe Vaginal: oral fluconazole or topical azole Oral or esophageal: nystatin S&S, clotrimazole troche, or oral fluconazole Systemic: fluconazole, echinocandins, or amphotericin B Histoplasmosis Itraconazole (limited disease) -or- Blastomycosis Amphotericin B (severe disease) Coccidioidomycosis Sporotrichosis Paracoccidioidomycosis Itraconazole (limited disease) -or- Amphotericin B (severe disease) -or- If CNS Involvement: SMX/TMP or Amphotericin B Fungal Infections Infection Treatment of Choice Tinea Topical azoles or topical tolnaftate (superficial epidermal infections) -or- dermatophytes Oral azoles or oral terbinafine (deeper infections: follicles, dermis, nails) *Nystatin is NOT effective. Avoid concurrent topical steroids. Candidiasis Skin: nystatin or clotrimazole topical or oral fluconazole if severe Vaginal: oral fluconazole or topical azole Oral or esophageal: nystatin S&S or clotrimazole troche or oral fluconazole Systemic: fluconazole, echinocandins, or amphotericin B Histoplasmosis Itraconazole (limited disease) -or- Blastomycosis Amphotericin B (severe disease) Coccidioidomycosis Sporotrichosis Paracoccidioidomycosis Itraconazole (limited disease) -or- Amphotericin B (severe disease) -or- If CNS Involvement: SMX/TMP or Amphotericin B  Dermatologic Infections Bacterial infections Fungal infections Viral infections Cellulitis Tinea group Herpes simplex Erysipelas Candidiasis Varicella Folliculitis/Furuncle/Carbuncle Histoplasmosis Impetigo Blastomycosis Endoparasitic infections Leprosy Paracoccidioidomycosis American Trypanosomiasis Cutaneous Anthrax Sporotrichosis Babesiosis Coccidioidomycosis Hookworms & Threadworms Schistosomiasis Lice Scabies Antivirals acyclovir/valacyclovir: guanosine analogs that cause chain termination by inhibiting viral DNA polymerase Adverse Events: Obstructive crystalline nephropathy & AKI if not adequately hydrated Viral Infections Infection Treatment of Choice Herpes Simplex Oral valacyclovir (or acyclovir). Can be given for acute episodes or chronic suppression. Varicella Oral acyclovir -or- valacyclovir if within 3 days of lesion onset. *no benefit if all lesions have crusted Generally, not given for healthy children 12 & under. Immunocompromised & pregnant patients are candidates. IV therapy if varicella-complications (hepatitis, PNA, encephalitis). Zoster Oral acyclovir-or- valacyclovir if within 3 days of lesion onset. *no benefit if all lesions have crusted Consider starting antivirals beyond 3 days if immunocompromised, lesions with complications (V1 dermatome), age > 65 years, or new lesions are still forming. PNA: pneumonia Not for this Exam, but for Rotations: Treatment Approach for Genital Herpes Simplex https://www.cdc.gov/std/treatment-guidelines/pocket-guide.pdf 35 Not for this Exam, but for Rotations: Treatment Approach for Genital Herpes Simplex https://www.cdc.gov/std/treatment-guidelines/pocket-guide.pdf 36  Dermatologic Infections Bacterial infections Fungal infections Viral infections Cellulitis Tinea group Herpes simplex Erysipelas Candidiasis Varicella Folliculitis/Furuncle/Carbuncle Histoplasmosis Impetigo Blastomycosis Endoparasitic infections Leprosy Paracoccidioidomycosis American Trypanosomiasis Cutaneous Anthrax Sporotrichosis Babesiosis Coccidioidomycosis Hookworms & Threadworms Schistosomiasis Lice Scabies Endoparasitic infections Infection Treatment of Choice Chagas Disease Benznidazole (better tolerated) or nifurtimox Babesiosis Atovaquone plus azithromycin Hookworm & Threadworm Albendazole or Mebendazole or pyrantel pamoate (or last resort: ivermectin) Schistosomiasis Praziquantel pyrantel pamoate & Albendazole & nifurtimox: atovaquone: praziquantel: ivermectin: mebendazole: converted to nitro- selective inhibitor of ↑ Ca2+ permeability depolarizing microtubule anion radical that parasite to ↑ vacuolization neuromuscular inhibitor to treat damages parasite mitochondrial blocking agent, “bendy” worms macromolecules electron transport thereby causing paralysis FUN FACT: Azithromycin, a macrolide antibiotic, kills parasites by inhibiting the bacterium-like apicoplast ribosomes & inhibiting parasite blood stage development. Endoparasitic infections Albendazole (most effective), Mebendazole & Benznidazole microtubule inhibitor to treat “bendy” worms MOA: Inhibits microtubule synthesis, leading to inhibition of glucose uptake, causing worm death For the curious: albendazole inhibits tubulin polymerization & mebendazole inhibits microtubule formation Side Effects: Generally minimal. If high & repeated dosing: increased liver enzymes, increased intracranial pressure, bone marrow suppression Pearls: One-time dose usually effective, but repeat doses often given Pinworms: treat family members Chaga’s Disease – American trypanosomiasis (protozoan) Hookworm & Threadworm (parasites) Endoparasitic infections Nifurtimox MOA: When metabolized, is converted to nitro-anion radicals that damages parasite macromolecules Side effects: Significant GI disturbances, rash, seizures. Overall, more poorly tolerated than other agents. Chaga’s Disease – American trypanosomiasis (protozoan) Endoparasitic infections Pyrantel Pamoate & Ivermectin (two different classes, similar MOA) MOA: neuromuscular blocking agent causing hyperpolarization of nerves & muscle, leading to paralysis and expulsion. For the curious: pyrantel pamoate via nicotinic acetylcholine receptors & ivermectin via glutamate-gated chloride channels. Side Effects: Topical: localized burning, skin irritation Systemic: CNS effects, delayed hypersensitivity (skin rash to SJS/TEN), Mazzoti reaction (immunologic post- treatment reaction – pruritis, rash, fever, fatigue, arthralgia, tachycardia, hypotension, abdominal pain) Pearls: For lice, scabies and nematodes Can use ivermectin if pyrantel pamoate allergy & vice versa Hookworm & Threadworm (parasitic worms) Endoparasitic infections Atovaquone MOA: selective inhibitor of mitochondrial electron transport Side effects: GI disturbances, rash, low-grade fever Pearls: Often given with Azithromycin. Azithromycin kills parasites by inhibiting the bacterium-like apicoplast ribosomes & inhibiting parasite blood stage development. Babesiosis (tick-borne protozoan) Endoparasitic infections Praziquantel MOA: disrupts ion transport by increasing cell membrane permeability to calcium, leading to increased vacuolization Side effects: GI disturbances, fatigue/drowsiness, skin rash, myalgia & arthralgia, low-grade fever Pearls: AVOID in ocular cysticercosis due to the damaging effects of the destruction of the parasites. AVOID in patients who need to stay alert (driving, etc.) due to S/E of drowsiness. AVOID during pregnancy. Schistosomiasis (parasitic worm)  Dermatologic Infections Bacterial infections Fungal infections Viral infections Cellulitis Tinea group Herpes simplex Erysipelas Candidiasis Varicella Folliculitis/Furuncle/Carbuncle Histoplasmosis Impetigo Blastomycosis Endoparasitic infections Leprosy Paracoccidioidomycosis American Trypanosomiasis Cutaneous Anthrax Sporotrichosis Babesiosis Coccidioidomycosis Hookworms & Threadworms Schistosomiasis Lice Scabies Lice Treatment (1st Line): TOPICAL Permethrin 1% or Pyrethrens/piperonyl butoxide or Spinosad Mechanisms of Action: Permethrin & pyrenthrens (OTC): Disrupts sodium transport across neuronal membranes, causing neurotoxicity & paralysis (including respiratory). These agents are CONTRAINDICATED in patients with Chrysanthemum allergy. Piperonyl butoxide: synergistic with pyrethrins by inhibiting mixed-function oxidase (CYP450) metabolism of the neurotoxin Spinosad (Rx): Mixture of spinosyn A & D that causes neuronal hyperexcitation (through acetylcholine receptors) causing muscle contractions and paralysis Pearls: Must comb nits out also. Remember to treat bedding, clothing, seams of clothing, stuffed animals, etc. Repeat in 7 days (give refills). Can cause skin irritation. Scabies Treatment (1st Line): Topical Permethrin or Topical Spinosad or Oral Ivermectin Mechanisms of Action: Permethrin 5% (Rx): Disrupts sodium transport across neuronal membranes, causing neurotoxicity & paralysis (including respiratory). These agents are CONTRAINDICATED in patients with Chrysanthemum or Ragweed allergy. Spinosad (Rx): Mixture of spinosyn A & D that causes neuronal hyperexcitation (through acetylcholine receptors) causing muscle contractions and paralysis. Ivermectin (Rx): ORAL USE. Neuromuscular blocking agent causing hyperpolarization of nerves & muscle, leading to paralysis. NOT 1st line in pregnancy or children weighing azith). Acne vulgaris: Overview of management - UpToDate References/Reading: Sanford Guide: Sanford Guide (openathens.net) Infectious Disease Society of America (IDSA) Guidelines: IDSA Practice Guidelines (idsociety.org) Antiparasitic Infections & Treatment review by the National Library of Medicine (NLM): Antiparasitic Drugs - StatPearls - NCBI Bookshelf (nih.gov) And if all else fails: Current Medical Diagnosis & Treatment 2024 | AccessMedicine | McGraw Hill Medical (okstate.edu)