Antimicrobial Agents: Tetracyclines and Antifungals
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Questions and Answers

What is the objective of this lecture?

The objective of the lecture is to discuss the pharmacology of broad-spectrum antibiotics, Tetracyclines and Chloramphenicol and pharmacology of antifungal drugs.

Which of the following are considered broad-spectrum antibiotics?

  • Tetracyclines (correct)
  • Chloramphenicol (correct)
  • Antifungal drugs

    • What is the mechanism of action of tetracyclines?

    Tetracyclines inhibit protein synthesis by binding to the 30S ribosome in susceptible organisms, inhibiting the binding of aminoacyl tRNA to mRNA, ultimately preventing the growth of the peptide chain.

    What is the primary source of tetracyclines?

    <p>Soil actinomycetes</p> Signup and view all the answers

    Tetracyclines are primarily bacteriocidal.

    <p>False</p> Signup and view all the answers

    The indiscriminate use of tetracyclines has led to the development of resistant strains.

    <p>True</p> Signup and view all the answers

    What is the primary route of administration for tetracyclines?

    <p>Oral</p> Signup and view all the answers

    Tetracyclines are generally well absorbed in the presence of food.

    <p>False</p> Signup and view all the answers

    Which of the following is NOT a commonly reported adverse effect of tetracyclines?

    <p>Hemolytic anemia</p> Signup and view all the answers

    What precautions should be taken when administering tetracyclines?

    <p>Tetracyclines should not be used during pregnancy, lactation, or in children. Cautious use is advised in patients with renal or hepatic insufficiency. It's essential to never use tetracyclines beyond their expiry date.</p> Signup and view all the answers

    What is the mechanism of action of chloramphenicol?

    <p>Chloramphenicol is bacteriostatic and binds to the 50S ribosome, inhibiting protein synthesis.</p> Signup and view all the answers

    Chloramphenicol is particularly effective against Salmonella typhi.

    <p>True</p> Signup and view all the answers

    What is a major concern associated with the use of chloramphenicol?

    <p>Aplastic anemia</p> Signup and view all the answers

    What are some of the common uses of chloramphenicol?

    <p>Chloramphenicol is primarily used for treating pyogenic meningitis and enteric fever.</p> Signup and view all the answers

    What are some examples of fungal infections that are commonly treated with antifungal drugs?

    <p>Common fungal infections include candidiasis, dermatophytosis, aspergillosis, and leishmaniasis.</p> Signup and view all the answers

    Define 'Fungus'.

    <p>A plant-like organism that does not make chlorophyll. Examples include mushrooms, yeasts, and molds.</p> Signup and view all the answers

    Fungal infections have become more prevalent since the 1950s due to the use of broad-spectrum antibiotics, corticosteroids, and immunosuppressant drugs.

    <p>True</p> Signup and view all the answers

    What is the mechanism of action of amphotericin B?

    <p>Amphotericin B is fungicidal and works by binding to ergosterol, a component of fungal cell membranes, forming pores that allow for the leakage of essential ions and molecules, leading to cell death.</p> Signup and view all the answers

    Amphotericin B is considered one of the most toxic antibiotics.

    <p>True</p> Signup and view all the answers

    What are some of the common uses of amphotericin B?

    <p>Amphotericin B is effective against a wide range of yeasts and fungi, including Candida, Histoplasma, and Aspergillus. It's also used for the treatment of leishmaniasis, a parasitic disease.</p> Signup and view all the answers

    What is the primary route of administration for amphotericin B?

    <p>Intravenous</p> Signup and view all the answers

    What is the mechanism of action of caspofungin?

    <p>Caspofungin inhibits the synthesis of the beta-1,3 glucan component of fungal cell walls by inhibiting the enzyme beta-glucan synthase, leading to fungal cell death.</p> Signup and view all the answers

    Caspofungin is a prototype member of the echinocandin class of antifungal drugs.

    <p>True</p> Signup and view all the answers

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

    <p>Hepatitis</p> Signup and view all the answers

    What are the common uses of caspofungin?

    <p>Caspofungin is used for the treatment of deep and invasive candidiasis and aspergillosis.</p> Signup and view all the answers

    Describe the mechanism of action of griseofulvin.

    <p>Griseofulvin interferes with the mitotic process of fungi, inhibiting their growth and development.</p> Signup and view all the answers

    Griseofulvin is effective against both Candida and deeper mycoses.

    <p>False</p> Signup and view all the answers

    Griseofulvin is absorbed more effectively when taken with a fatty meal.

    <p>True</p> Signup and view all the answers

    What is the primary use of griseofulvin?

    <p>Griseofulvin is mainly used for the treatment of dermatophytosis, which includes fungal infections of the skin, nails, and hair.</p> Signup and view all the answers

    What is the mechanism of action of imidazoles and triazoles?

    <p>Imidazoles and triazoles inhibit the fungal cytochrome P450 enzyme, lanosterol 14-demethylase, which is essential for ergosterol synthesis. The impairment of ergosterol synthesis leads to membrane abnormalities, resulting in fungistatic and fungicidal effects.</p> Signup and view all the answers

    Imidazoles and triazoles have a high affinity for mammalian cytochrome enzymes, resulting in significant toxicity.

    <p>False</p> Signup and view all the answers

    What are some of the common uses of clotrimazole?

    <p>Clotrimazole is a topical imidazole drug used for treating Tinea infections (ringworms), otomycosis, and oral and vaginal candidiasis.</p> Signup and view all the answers

    What are some of the common uses of miconazole?

    <p>Miconazole is highly efficacious for treating Tinea and otomycosis, as well as oral and vaginal candidiasis. It has good penetration into the skin and nails.</p> Signup and view all the answers

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

    <p>Hemolytic anemia</p> Signup and view all the answers

    Ketoconazole can interact with various medications, including those metabolized by the cytochrome P450 system.

    <p>True</p> Signup and view all the answers

    Fluconazole's bioavailability is significantly influenced by food intake.

    <p>False</p> Signup and view all the answers

    What is the mechanism of action of terbinafine?

    <p>Terbinafine is fungicidal and works as a non-competitive inhibitor of squalene epoxidase. This inhibition leads to an accumulation of squalene within fungal cells, ultimately causing fungal cell death.</p> Signup and view all the answers

    Terbinafine has a high affinity for keratin.

    <p>True</p> Signup and view all the answers

    What are some of the common uses of terbinafine?

    <p>Terbinafine is used topically and orally for the treatment of dermatophytosis, fungal infections affecting the skin, nails, and hair. It's also used for treating onychomycosis, a fungal infection of the nails.</p> Signup and view all the answers

    Tolnaftate is the preferred treatment for fungal infections involving the nails and soles.

    <p>False</p> Signup and view all the answers

    What are some of the common uses of tolnaftate?

    <p>Tolnaftate is used topically for treating dermatophytosis, specifically Tinea cruris and corporis.</p> Signup and view all the answers

    Ciclopirox oleamine is a newer antifungal drug with excellent systemic absorption.

    <p>False</p> Signup and view all the answers

    What are some of the common uses of ciclopirox oleamine?

    <p>Ciclopirox oleamine is used for treating Tinea infections, Pityriasis versicolor, onchomycosis, and vaginal candidiasis.</p> Signup and view all the answers

    What is candidiasis?

    <p>Candidiasis is a fungal infection caused by an overgrowth of Candida albicans, a type of yeast commonly found on the skin, vagina, and mouth.</p> Signup and view all the answers

    Which type of candidiasis affects the skin in folds, like underarms and under breasts?

    <p>Cutaneous candidiasis</p> Signup and view all the answers

    What is the common name for oral candidiasis?

    <p>Oral candidiasis is commonly known as thrush.</p> Signup and view all the answers

    Candida granuloma is typically a mild fungal infection.

    <p>False</p> Signup and view all the answers

    Invasive candidiasis occurs due to a weakened immune system or an uncontrolled medical condition.

    <p>True</p> Signup and view all the answers

    Study Notes

    Antimicrobial Agents: Tetracyclines, Chloramphenicol, and Antifungals

    • Antibiotics are compounds produced by microorganisms that inhibit other microorganisms.
    • Tetracyclines are a class of antibiotics with a nucleus of 4 cyclic rings. They are obtained from soil actinomycetes and are broad-spectrum antibiotics.
    • Tetracyclines inhibit protein synthesis by binding to 30S ribosomes in susceptible organisms, preventing the binding of aminoacyl tRNA to mRNA, thus hindering peptide chain growth.
    • Tetracyclines have a wide antimicrobial spectrum initially, but indiscriminate use has led to the development of antibiotic resistance in numerous species.
    • Common tetracycline types are demeclocycline, minocycline, and doxycycline.
    • Doxycycline has better oral bioavailability and isn't affected by food chelates as much as other tetracyclines.
    • Tetracyclines are administered orally and widely distributed in the body. They are mainly excreted by the kidneys.
    • Adverse effects of tetracyclines may include: epigastric pain, nausea, vomiting, diarrhea, hepatotoxicity (fatty liver infiltration, jaundice), nephrotoxicity. (renal problems excluding Doxycycline), phototoxicity, tooth discoloration, hyper sensitivity. These problems can be more severe with degraded tetracycline use.
    • Tetracyclines should not be used during pregnancy, lactation, or in children, and caution is advised in renal or hepatic insufficiency patients.
    • Chloramphenicol is an older antibiotic, initially derived from bacteria, now chemically synthesized.
    • Chloramphenicol's mechanism of action is bacteriostatic, binding to 50S ribosome and inhibiting protein synthesis. It's similar to other tetracyclines in spectrum, but highly effective against Salmonella typhi.
    • Chloramphenicol is rapidly absorbed orally, and conjugated by the liver with glucuronic acid. Use with caution in patients with cirrhosis and/or immature livers (neonates).
    • Adverse effects of Chloramphenicol include bone marrow suppression (aplastic anemia, agranulocytosis), myelosuppression, and idiosyncratic reactions, including fatal aplastic anemia.
    • Uses for Chloramphenicol are extremely limited due to resistant strains and safer alternatives. It’s currently used in pyogenic meningitis and enteric fever.
    • Antifungal drugs treat both superficial and deep (systemic) mycosis.
    • Fungal infections emerged in the 1950s due to the use of broad-spectrum antibiotics, corticosteroids, chemotherapy, and immunosuppressants, and the emergence of AIDS.
    • Antifungal drugs include polyenes, azoles, allylamines, and echinocandins.
    • Amphotericin B is a polyene antibiotic with numerous double bonds that inhibits fungi, specifically targeting ergosterol in fungal membranes.
    • The administration of Amphotericin B is done intravenously.
    • Adverse effects of Amphotericin B are usually dose-dependent acute/short-term (chills, fever, pain, nausea, vomiting, dyspnea) and long-term nephritis, and potentially fatal bone marrow suppression.
    • Liposomal Amphotericin B formulations have decreased toxicity compared to standard Amphotericin B.
    • Nystatin is another polyene antibiotic, derived from Streptomyces noursei, with similar properties to Amphotericin B but with higher systemic toxicity.

    Antifungal Drug Classifications

    • Polyenes:
      • Amphotericin B
      • Nystatin
    • Azoles:
      • Clotrimazole
      • Miconazole
      • Oxiconazole
      • Ketoconazole
      • Fluconazole
      • Itraconazole
      • Voriconazole
    • Allylamines:
      • Terbinafine
    • Echinocandins:
      • Caspofungin
    • Griseofulvin

    Specific Antifungal Drug Details

    • Griseofulvin:
      • Fungistatic and effective against dermatophytes.
      • Poor oral absorption; better absorption with fatty meals.
      • Keratophilic, deposits in keratin-producing cells of skin, nails, and hair and persists for weeks.
    • Fluconazole:
      • Water-soluble triazole with good oral bioavailability.
      • Less anti-androgenic activity compared to other drugs, less likely to cause undesirable hormonal effects.
    • Itraconazole:
      • Variable oral absorption; affected by food and gastric acid.
    • Voriconazole:
      • Second-generation broad-spectrum azole; used for invasive fungal infections like aspergillosis, candidiasis, histoplasmosis, and blastomycosis.
    • Terbinafine:
      • Orally and topically active against dermatophytes and candida spp.
      • Inhibits squalene epoxidase.
    • Tolnaftate:
      • Poor skin penetration; primarily topical.
    • Ciclopirox olamine:
      • Newer for tinea infections, good keratin penetration but poor systemic absorption.

    Candidiasis

    • Candidiasis is a fungal infection caused by Candida albicans.
    • Different types of candidiasis exist based on location
    • Vaginal, Oral, Cutaneous, Invasive infections, and Candida granuloma.

    Antifungal Drug Administration, Toxicity, and Uses

    • Amphotericin B is usually administered intravenously (IV).
    • Administration of other antifungal drugs such as fluconazole is usually oral.
    • Many antifungal drugs show some degree of toxicity, including acute, short-term effects (chills, pain, vomiting) and more severe, longer-term adverse effects like kidney damage.
    • Careful attention to patient needs and treatment response are essential to managing fungal infections.

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    Tetracyclines, Anti-fungals (Lecture 77) - PDF

    Description

    This quiz covers key concepts related to antimicrobial agents, focusing on tetracyclines and antifungals. You'll learn about the mechanism of action of tetracyclines, their spectrum, and issues related to antibiotic resistance. Additionally, it touches on common types of tetracyclines and their pharmacokinetics.

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