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Antifungal agents
1. Fungal infections are common in immunocompromised patients and those taking immunosuppressive drugs. They are harder to treat than bacterial infections. 2. There are two main types of fungal infections - superficial infections affecting the skin and mucous membranes, and deep infections affecting internal organs like the lungs and brain. 3. Major antifungal drug classes include azoles like fluconazole and itraconazole, polyenes like amphotericin B, and allylamines like terbinafine. They work by disrupting the fungal cell membrane or inhibiting fungal enzyme activity.
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Antifungal agents
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- 2. ANTIFUNGAL AGENTS • commonin Diabetes Mellitus, Cancer, AIDS, Pregnancy and in patients on immunosuppressive therapy such as prolonged course of corticosteriods, broad spectrum antibiotics, anticancer drugs, etc. • Treatment of fungal infections is somewhat difficult than bacterial infection because of various factors.
- 3. Antifungal Drugs • Fungalinfectious occur due to : • 1- Abuse of broad spectrum antibiotics • 2- Decrease in the patient immunity
- 4. FUNGAL INFECTIONS/CAUSATIVE ORGANISMS SUPERFICIAL MYCOSIS •Dermatophytes • Epidermophyton • Trichophyton • Microsporum • Candida • Malassezia Furfur DEEP MYCOSIS • Asperigillus • Blastomyces • Cryptococcus • Coccidioides • Candida • Histoplasma • Mucormycosis • Sporotrichosis
- 5. Types of fungalinfections • 1. Superficial : Affect skin – mucous membrane. e.g. • Dermatophytes : Fungi that affect keratin layer of skin, hair, nail.e.g.tinea pedis ,ring worm infection • Candidiasis : Yeast-like, oral thrush, vulvo-vaginitis , nail infections.
- 6. 2- Deep infections •Affect internal organs as : – Lung – Heart – Brain – Endocarditis – Meningitis.
- 7. 1. ANTIBIOTICS A)Polyenes: amphotericinB, Nystatin, Hamycin, Natamycin B)Heterocyclic Benzofuran: Griseofulvin 2. Antimetabolite: Flucytosine (5-FC) 3. Azoles: A)Imidazoles (topical): Clotrimazole, Econazole, Miconazole, Oxiconazole. Systemic: ketoconazole. B)Trizoles (systemic): Fluconazole, Itraconazole, Voriconazole. Classification of Antifungal Drugs
- 8. 4. Allylamine: Terbinafine 5.Other topical agents: Tolnaftate Undecylenic acid Benzoic acid Quiniodochlor Ciclopirox olamine Butenafine Sodium thiosulfate.
- 10. Classification According toRoute of Administration • Systemic : • Griseofulvin , Amphotericin- B , Ketoconazole , Fluconazole , Terbinafine. • Topical • In candidiasis : • Imidazoles : Ketoconazole , Miconazole. • Triazoles : Terconazole. • Polyene macrolides : Nystatin , Amphotericin-B • Gentian violet : Has antifungal & antibacterial.
- 12. Amphotericin B • AmphotericinA & B are antifungal antibiotics. • Amphotericin A is not used clinically. • It is a natural polyene macrolide • (polyene = many double bonds ) • (macrolide = containing a large lactone ring )
- 13. Pharmacokinetics • Poorly absorbedorally, is effective for fungal infection of gastrointestinal tract. • For systemic infections given as slow I.V.I. • Highly bound to plasma protein . • Poorly crossing BBB. • Metabolized in liver • Excreted slowly in urine over a period of several days. • Half-life 15 days.
- 14. Mechanism of action •It is a selective fungicidal drug. • Disrupt fungal cell membrane by binding to ergosterol , so alters the permeability of the cell membrane leading to leakage of intracellular ions & macromolecules ( cell death ).
- 18. Resistance to AmphotericinB • If ergosterol binding is impaired either by : • Decreasing the membrane concentration of ergosterol. • Or by modyfing the sterol target molecule.
- 19. Adverse Effects 1- Immediatereactions ( Infusion –related toxicity ). Fever, muscle spasm, vomiting ,headache, hypotension. Can be avoided by : A. Slowing the infusion B. Decreasing the daily dose C. Premedication with antipyretics, antihistamincs or corticosteroids.
- 20. Slower toxicity • Mostserious is renal toxicity (nearly in all patients ). • Hypokalemia • Hypomagnesaemia • Impaired liver functions • Thrombocytopenia • Anemia
- 21. Clinical uses • Hasa broad spectrum of activity • Fungicidal action. • The drug of choice for life-threatening mycotic infections. • Also, for chronic therapy & preventive therapy of relapse. • In cancer patients with neutropenia who remain febrile on broad –spectrum antibiotics.
- 22. Routes of Administration •1- Slow I.V.I. For systemic fungal disease. • 2- Intrathecal for fungal C.N.S. infections. • Topical drops & direct subconjunctival injection for Mycotic corneal ulcers. • 3- Local injection into the joint in fungal arthritis. • 4- Bladder irrigation in Candiduria.
- 23. Liposomal preparations ofamphotericin B • Amphotericin B is packaged in a lipid- associated delivery system to reduce binding to human cell membrane , so reducing : A. Nephrotoxicity B. Infusion toxicity • Also, more effective • More expensive
- 24. Azoles • A groupof synthetic fungistatic agents with a broad spectrum of activity . • They have antibacterial antiprotozoal anthelminthic antifungal activity .
- 26. Mechanism of Action 1-Inhibitthe fungal cytochrome P450 enzyme, (α-demethylase) which is responsible for converting lanosterol to ergosterol ( the main sterol in fungal cell membrane ). 2- Inhibition of mitochondrial cytochrome oxidase leading to accumulation of peroxides that cause autodigestion of the fungus. 3- Imidazoles may alter RNA& DNA metabolism.
- 27. Imidazoles • Ketoconazole • Miconazole •Clotrimazole • They lack selectivity ,they inhibit human gonadal and steroid synthesis leading to decrease testosterone & cortisol production. • Also, inhibit human P-450 hepatic enzyme.
- 28. Ketoconazole • Well absorbedorally . • Bioavailability is decreased with antacids, H2 blockers , proton pump inhibitors & food . • Cola drinks improve absorption in patients with achlorhydria. • Half-life increases with the dose , it is (7-8 hrs). • Inactivated in liver & excreted in bile (feces ) & urine. • Does not cross BBB.
- 29. Clinical uses Adverseeffects • Used topically or systematic (oral route only ) to treat : • 1- Oral & vaginal candidiasis. • 2- Dermatophytosis. • 3- Systemic mycoses & mucocutaneous candidiasis. • Nausea, vomiting ,anorexia • Hepatotoxic • Inhibits human P 450 enzymes • Inhibits adrenal & gonadal steroids leading to : • Menstrual irregularities • Loss of libido • Impotence • Gynaecomastia in males
- 30. Triazoles • Fluconazole • Itraconazole •Voriconazole • They are : • Selective • Resistant to degradation • Causing less endocrine disturbance
- 31. Fluconazole • Water soluble,Completely absorbed from GIT • Excellent bioavailability after oral administration • Bioavailability is not affected by food or gastric PH • Conc. in plasma is same by oral or IV route • Penetrates well BBB so, it is the drug of choice of cryptococcal meningitis • Safely given in patients receiving bone marrow transplants (reducing fungal infections) • Excreted mainly through kidney • Half-life 25-30 hours • Resistance is not a problem
- 32. Clinical uses • Candidiasis(is effective in all forms of mucocutaneous candidiasis) • Cryptococcus meningitis • Histoplasmosis, blastomycosis, , ring worm. • Not effective in aspergillosis Side effects • Nausea, vomiting, headache, skin rash , diarrhea, abdominal pain , reversible alopecia. • Hepatic failure may lead to death • Highly teratogenic ( as other azoles) • Inhibit P450 cytochrome • No endocrine side effects
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