L-23 Antifungal Agents and Pathogenic Fungi

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Questions and Answers

Which of these medications can be used to treat oral candidiasis?

  • Griseofulvin
  • Nizoral
  • Amphotericin B
  • Nystatin (correct)

Which of the following medications is not recommended for use in pregnancy?

  • Amphotericin B
  • Nizoral (correct)
  • Nystatin
  • Griseofulvin

Which medication listed inhibits mitosis at metaphase by disrupting spindle formation?

  • Nystatin
  • Amphotericin B
  • Nizoral
  • Griseofulvin (correct)

Which medication is specifically indicated for the treatment of tinea infections?

<p>Nizoral (A)</p> Signup and view all the answers

Which of these medications is primarily used for Candida infections of the mucosa, skin, intestinal tract, and vagina ?

<p>Nystatin (B)</p> Signup and view all the answers

Which of the following medications shares a similar structure and mechanism of action to Amphotericin B?

<p>Nystatin (B)</p> Signup and view all the answers

What is the primary role of polyene antibiotics like Amphotericin B in antifungal treatment?

<p>Form pores in the fungal cell membrane (C)</p> Signup and view all the answers

Which type of fungi is least likely to require prolonged antifungal therapy due to the nature of their infections?

<p>Superficial mycoses (C)</p> Signup and view all the answers

Which antifungal agent is classified as an echinocandin?

<p>Caspofungin (A)</p> Signup and view all the answers

What is the primary reason invasive mycosis infections are difficult to treat?

<p>They often occur in patients with underlying immunosuppression. (C)</p> Signup and view all the answers

Which of the following antifungal agents primarily targets the fungal cell wall?

<p>Echinocandins (B)</p> Signup and view all the answers

What mechanism do imidazole antifungal agents utilize against fungal infections?

<p>They disrupt the formation of fungal cell membranes. (B)</p> Signup and view all the answers

What enzyme is inhibited by azoles, leading to the disruption of fungal growth?

<p>Sterol 14-alpha demethylase (C)</p> Signup and view all the answers

Which of the following is NOT a common adverse effect associated with azole antifungals?

<p>Seizures (D)</p> Signup and view all the answers

Which azole is specifically noted for its use in the suppressive therapy of histoplasmosis in HIV seropositive patients?

<p>Itraconazole (C)</p> Signup and view all the answers

Which of the following conditions can fluconazole effectively treat?

<p>Oropharyngeal candidiasis (C)</p> Signup and view all the answers

What is a primary characteristic that differentiates itraconazole from ketoconazole?

<p>Water solubility (A)</p> Signup and view all the answers

Ketoconazole was the first antifungal agent available for what type of infections?

<p>Deep systemic mycoses (C)</p> Signup and view all the answers

Which azole is known for its effective activity against cryptococcal meningitis in AIDS patients?

<p>Fluconazole (A)</p> Signup and view all the answers

What is a major characteristic of imidazoles compared to triazoles?

<p>Specificity towards fungi (C)</p> Signup and view all the answers

What type of candidiasis does fluconazole specifically treat?

<p>Mucosal candidiasis (C)</p> Signup and view all the answers

Among the following, which is least likely to be used for deep systemic mycoses?

<p>Clotrimazole (C)</p> Signup and view all the answers

What is a primary clinical use of liposomal formulations of antifungal medications?

<p>Fungal meningitis and systemic infections (C)</p> Signup and view all the answers

What adverse effect is associated with the use of Amphotericin B?

<p>Flushing and chills (B)</p> Signup and view all the answers

Which fungi can be treated with Flucytosine?

<p>Cryptococcus and systemic candidiasis (D)</p> Signup and view all the answers

What is the mechanism of action of Flucytosine?

<p>Inhibits thymidylate synthase by converting to 5-FU (B)</p> Signup and view all the answers

Why are lipid formulations of amphotericin B preferred over conventional formulations?

<p>They have fewer adverse effects related to renal function (A)</p> Signup and view all the answers

Which azole antifungal is mentioned in the document?

<p>Imidazoles and triazoles (A)</p> Signup and view all the answers

What is a potential toxicity of Flucytosine?

<p>Dose-dependent GI effects (A)</p> Signup and view all the answers

What is the primary method of administering Amphotericin B in patients with meningitis?

<p>Intrathecally (B)</p> Signup and view all the answers

Flashcards

What is the mechanism of action of imidazoles and triazoles?

Imidazoles and triazoles are types of antifungal drugs that work by inhibiting the enzyme sterol 14-alpha demethylase, leading to disruption of fungal cell membrane formation.

Give some examples of imidazoles and triazoles.

Ketoconazole, miconazole, clotrimazole, fluconazole, and itraconazole are examples of commonly used antifungal drugs.

Antifungal Agents

Antifungal agents are medications used to treat fungal infections. They are categorized based on their mode of action and target specific fungal components, primarily the cell membrane or cell wall, to inhibit fungal growth and kill fungal cells.

What is Fluconazole’s main use in AIDS patients?

Fluconazole is particularly effective against Cryptococcus neoformans, a fungus that causes meningitis in immunocompromised patients, especially those with AIDS.

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Polyenes (e.g., Amphotericin B)

Polyenes, like amphotericin B, are a class of antifungal drugs that target the fungal cell membrane. Amphotericin B binds to ergosterol, a vital component of fungal membranes, forming pores that lead to cell leakage and death.

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What is Itraconazole used for?

Itraconazole is effective for treating deep mycoses (serious fungal infections) and is especially helpful for suppressing Histoplasma capsulatum infections in HIV-positive individuals.

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What is Ketoconazole, and how is it used?

Ketoconazole is a systemic imidazole antifungal that was one of the first oral drugs available for treating serious fungal infections. It is also effective against Candida albicans, which causes oral and pharyngeal candidiasis in patients with advanced AIDS.

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Flucytosine

Flucytosine, a synthetic antifungal drug, inhibits the synthesis of fungal DNA and RNA. It's often used in combination with amphotericin B.

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Griseofulvin

Griseofulvin is a antifungal drug that inhibits fungal cell division by interfering with microtubule formation. It's primarily used for dermatophyte infections.

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What are some potential side effects of imidazoles and triazoles?

Adverse effects of imidazole and triazole drugs include nausea, vomiting, gastric pain, headache, rashes, and more rarely, seizures, anaphylaxis, and exfoliative dermatitis.

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Imidazoles (e.g., Fluconazole)

Imidazoles, like fluconazole, are broad-spectrum antifungal drugs that also target the fungal cell membrane. They inhibit the synthesis of ergosterol, disrupting the fungal cell membrane.

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Echinocandins

Echinocandins, a newer class of antifungal drugs, target fungal cell wall synthesis. They inhibit the synthesis of glucan, a crucial component of the fungal cell wall.

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Amphotericin B (Fungizone)

A broad-spectrum antifungal medication used to treat various serious fungal infections including Candida, Histoplasma, Cryptococcus neoformans, Blastomyces dermatitidis, Histoplasma capsulatum, Coccidiodes immitis, Paracoccidioides, Aspergillus, Penicillium, and Mucormycosis.

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Lipid Formulations of Amphotericin B

A type of Amphotericin B that is less toxic to the kidneys than the conventional form. It binds to mammalian membranes less readily, reducing kidney damage.

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Flucytosine (Ancobon)

An antifungal medication that functions as an antimetabolite. It is converted to 5-fluorouracil (5-FU) by cytosine deaminase, which inhibits thymidylate synthase, an enzyme crucial for DNA synthesis.

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Azoles (Imidazoles and Triazoles)

A class of antifungal medications that target fungal cell membranes, primarily the ergosterol biosynthesis pathway. They disrupt the formation of ergosterol, a vital component of fungal cell membranes, leading to fungal cell death.

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Imidazoles

A type of azole antifungal used to treat various fungal infections, especially Candida infections.

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Triazoles

A type of azole antifungal used to treat a wider range of fungal infections, including systemic mycoses.

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Systemic Fungal Infection

A severe fungal infection that can affect several organs, often caused by various fungal species, particularly Candida, Cryptococcus neoformans, and Aspergillus.

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Fungal Meningitis

A type of fungal infection that primarily affects the membranes surrounding the brain and spinal cord, often caused by Cryptococcus neoformans.

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What is a common antifungal drug used to treat tinea infections?

A broad-spectrum antifungal drug effective against dermatophytes, yeasts, dimorphic fungi, eumycetes, and actinomycetes. Commonly used to treat tinea infections.

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What antifungal drug is primarily used for Candida infections and administered orally?

An antifungal medication primarily used for Candida infections of the mucosa, skin, intestinal tract, and vagina. It's given orally but never parenterally (injection).

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How does Griseofulvin exert its antifungal effect and what is its primary use?

A fungistatic agent that disrupts microtubule function and inhibits mitosis at metaphase. It binds to keratin and is primarily used for systemic treatment of skin, hair, and nail infections caused by dermatophytes.

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What are some adverse effects associated with prolonged use of Nizoral?

Adverse effects include endocrinological abnormalities due to inhibition of steroid biosynthesis, which can lead to decreased libido and gynecomastia. Other adverse effects include hepatitis after prolonged treatment. Not recommended in pregnancy and nursing mothers.

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What fungal species are commonly targeted by Nystatin?

It is active against Cryptococcus, Candida, Histoplasma, Blastomyces, and dermatophytes like Epidermophyton, Trichophyton, and Microsporum.

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What is the primary clinical application of topical Nystatin?

Topical nystatin is the preferred treatment for oral candidiasis (thrush), denture stomatitis, and intestinal and pharyngeal candidiasis.

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Study Notes

Antifungal Agents

  • Many fungal infections are self-limiting and don't need chemotherapy
  • Superficial mycoses are often treated topically to limit host toxicity
  • Invasive or systemic fungal infections requiring prolonged antifungal use are often associated with underlying immunosuppression
  • Invasive mycoses are among the most difficult infectious diseases to treat successfully

Pathogenic Fungi

  • Superficial and subcutaneous fungi: Dermatophytes, Malassezia, Sporothrix, and Pigmented Molds
  • Opportunistic fungi: Candida, Aspergillus, Zygomycetes, and Pneumocystis
  • Systemic fungal pathogens: Cryptococcus, Histoplasma, Blastomyces, Coccidioides, and Paracoccidioides

Prototype Drugs

  • Polyenes: Amphotericin B (Fungizone, Abelcet, AmBisome, Amphotec), Nystatin (Mycostatin)
  • Flucytosine (5-FC, Ancobon)
  • Griseofulvin (Grifulvin, Grisactin, Fulvicin)
  • Imidazoles: Clotrimazole, Fluconazole, Itraconazole, Ketoconazole, Miconazole, and many more
  • Echinocandins: Anidulafungin, Micafungin, Caspofungin
  • Terbinafine (Lamisil)
  • Butenafine, Haloprogin, Naftifine, Natamycin, Tolnaftate

Targets of Antifungal Drugs

  • Most antifungals target the fungal cell membrane or cell wall
  • Flucytosine and Griseofulvin are exceptions

Amphotericin B (Ablecet, Ambisome, Amphocin, Fungizone, Amphotec)

  • Polyene antibiotic from Streptomyces
  • Mechanism of action: Forms pores in the fungal membrane, making it permeable to ions, causing leakage
  • Clinical uses: Various severe fungal infections (Candida, Histoplasma, Cryptococcus, Blastomyces, Coccidioides, etc.)
  • Adverse effects: Flushing, chills, fever, phlebitis, headache, anemia, reversible decreased renal function (nephrotoxicity), azotemia

Flucytosine (Ancobon)

  • Fluorinated pyrimidine related to fluorouracil
  • Mechanism: Deaminated to 5-fluorouracil (5-FU), inhibiting thymidylate synthase
  • Clinical use: Systemic candidiasis, cryptococcal infections, chromomycosis
  • Adverse effects: Reversible bone marrow suppression, dose-dependent GI effects

Imidazoles and Triazoles

  • Azole antifungals (Imidazoles and Triazoles) with similar spectra and mechanisms of action
  • Mechanism of action: Inhibit fungal ergosterol biosynthesis, disrupting phospholipid packing
  • Drugs: Ketoconazole, Miconazole, Clotrimazole, Butoconazole, Tioconazole, Oxiconazole, Sulconazole, Itraconazole, Fluconazole, Posaconazole, Terconazole
  • Itraconazole (Sporanox): Water-soluble triazole, used for deep mycoses and histoplasmosis in HIV-positive patients; similar to ketoconazole but more fungal specific
  • Fluconazole (Diflucan): Water-soluble imidazole, effective against various fungal infections especially for immunocompromised patients and cryptococcal meningitis.

Ketoconazole (Nizoral)

  • Commonly used orally for deep systemic mycoses, including Candida (oral and pharyngeal) in advanced AIDS
  • Metabolites appear in feces
  • Adverse effects: Endocrine abnormalities (decreased libido, gynecomastia), hepatitis in some patients after prolonged treatment; not recommended for pregnancy or nursing mothers

Nystatin (Mycostatin, Biostatin, Nyamyc, Nystat, tablet, and troche)

  • Structure and mechanism similar to Amphotericin B
  • Active against: Cryptococcus, Candida, Histoplasma, Blastomyces, dermatophytes (Epidermophyton, Trichophyton, Microsporum)
  • Given orally (not parenterally)
  • Topically used for oral moniliasis, thrush, denture stomatitis, and intestinal/pharyngeal candidiasis

Griseofulvin (Fulvicin, Grifulvin, Grisactin, Fulvin P/G)

  • Fungistatic agent insoluble in water
  • Mechanism: Disrupts mitosis by interfering with spindle formation
  • Clinical use: Diseases of the skin, hair, and nails due to Microsporum, Epidermophyton, and Trichophyton
  • Adverse effects: Neurological disturbances (mostly headache); hepatic microsomal enzyme induction; hematologic disorders (like leukopenia, neutropenia); vasodilation

Echinocandins (Anidulafungin, Micafungin, Caspofungin)

  • Anidulafungin: Inhibits fungal glucan synthase, crucial for cell wall synthesis
  • Micafungin: Intravascular use for esophageal candidiasis, candidemia, acute disseminated candidiasis, Candida infections; prophylaxis in stem cell transplant recipients.
  • Caspofungin: Mucosal and invasive candidiasis; invasive aspergillosis, Pneumocystis carinii infection

Terbinafine (Lamisil)

  • Inhibits fungal squalene epoxidase
  • Effective orally for onychomycosis and aspergillosis
  • Also approved for tinea capitis
  • Decreased risk of hepatotoxicity compared to itraconazole

Other Antifungals

  • Ciclopirox (Loprox): Broad spectrum antimycotic (cream or lotion)
  • Haloprogin (Halotex): Topical solution (discontinued)
  • Tolnaftate (Aftate, Tinactin, Ting): Topical cream/powder/aerosol for dermatophyte infections
  • Naftifine (Naftin): Topical allylamine, targeting squalene epoxidase
  • Undecylenic acid (Cruex, Desenex): Fatty acid with fungistatic activity for topical use
  • Butenafine (Mentax): Benzylamine related to allylamine; topical for superficial dermatophytosis

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