Antibiotics part 3
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Antifungal antibiotics Griseofulvin Polyenes
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Antibiotics part 3
- 2. • Fungal infections are normally less virulent in nature. • There are very few antifungal antibiotics that can be used systemically.
- 3. Infections antifungals can treat • Fungal infections commonly treated with antifungals include: • ringworm • athlete's foot • fungal nail infection • vaginal thrush • some kinds of severe dandruff • serious fungal infections: (develop deep inside the body tissues) • aspergillosis, which affects the lungs • fungal meningitis, which affects the brain
- 4. Types of antifungal medicines • Antifungal medicines are available as: • Topical antifungals – a cream, gel, ointment or spray you can apply directly to your skin, hair or nails • Oral antifungals – a capsule, tablet or liquid medicine that you swallow • Intravenous antifungals – an injection into a vein in your arm, usually given in hospital • Intravaginal antifungal pessaries – small, soft tablets you can insert into the vagina
- 5. How antifungal medicines work • Antifungal medicines work by either: • killing the fungal cells – for example, by affecting a substance in the cell walls, causing the contents of the fungal cells to leak out and the cells to die • preventing the fungal cells growing and reproducing
- 6. • Different classes of drugs target the plasma membrane, sterol biosynthesis, DNA biosynthesis, and β-glucan biosynthesis • Fungal membranes and sterol biosynthetic enzymes are different enough from ours that these agents can kill fungi but not us • Fungi make β-glucan, we don’t, so drugs that target β-glucan biosynthesis have low side-effects
- 7. Antifungal Medicines • Amphotericin • Flucytosine • Itraconazole • Voriconazole • Caspofungin • Micafungin • Clotrimazole • Econazole • Miconazole • Terbinafine • Fluconazole • Ketoconazole
- 8. Griseofulvin • Penicillium griseofulvum • Griseofulvin was first isolated in 1939. • Its antifungal activity was discovered in 1958. • It is active against the dermatophytic fungi, i.e. those such as Trichophyton causing ringworm. Penicillium patulum
- 9. • Ineffective against Candida albicans (Yeast) • causative agent of oral thrush and intestinal candidiasis • There is no disturbance of the normal bacterial flora of the gut. • Griseofulvin is administered orally in the form of tablets
- 10. • Griseofulvin -deposited in the deeper layers of the skin and in hair keratin. • Employed in chemotherapy
- 11. Side Effects • Loss of taste sensation • Nausea • Yeast infection in mouth • Diarrhoea • Dizziness • Fatigue • Headache • Skin rashes • Swelling • Impairment of liver enzymatic activity Brand Names • Crivicin • Grifulvin V • Gris OD 375 • Gris-PEG • Grison-250 • Grisovin-FP • S-Fulvin
- 12. Polyenes • Characterized by possessing a • large ring -containing a lactone group and • a hydrophobic region -consisting of a sequence of four to seven conjugated double bonds. • The most important polyenes are nystatin and amphotericin B. Ergosterol: the main sterol in the fungal cell membrane depolarization of the membrane increases the membrane permeability leads to cell death
- 13. • Nystatin has a specific action on C. albicans only. • poorly absorbed from the gastrointestinal tract. • administered orally in the treatment of oral thrush and intestinal candidiasis infections.
- 14. • Amphotericin B is particularly effective against systemic infections caused by C. albicans and Cryptococcus neoformans. • poorly absorbed from the gastrointestinal tract; • administered by intravenous injection • Amphotericin B methyl ester is water-soluble, unlike amphotericin B itself, and can be administered intravenously as a solution.
Editor's Notes
- Fungal infections are normally less virulent in nature than are bacterial or viral ones but may, nevertheless, pose a problem in individuals with a depressed immune system. In contrast to the wide range of antibacterial antibiotics, there are very few antifungal antibiotics that can be used systemically. Lack of toxicity is, as always, of paramount importance, but the differences in structure of, and some biosynthetic processes in, fungal cells mean that antibacterial antibiotics are usually inactive against fungi. Athlete’s foot Ringworm (circular red flat sore) Yeast infections
- Less commonly, there are also more serious fungal infections that develop deep inside the body tissues, which may need to be treated in hospital. You're more at risk of getting one of these more serious fungal infections if you have a weakened immune system – for example, if you're taking medicines to suppress your immunity.
- Antifungals work by exploiting differences between mammalian and fungal cells to kill the fungal organism with fewer adverse effects to the host. Unlike bacteria, both fungi and humans are eukaryotes. Thus, fungal and human cells are similar at the biological level. This makes it more difficult to discover drugs that target fungi without affecting human cells. As a consequence, many antifungal drugs cause side-effects. Some of these side-effects can be life-threatening if the drugs are not used properly.
- Antifungals work by exploiting differences between mammalian and fungal cells to kill the fungal organism with fewer adverse effects to the host. Unlike bacteria, both fungi and humans are eukaryotes. Thus, fungal and human cells are similar at the biological level. This makes it more difficult to discover drugs that target fungi without affecting human cells. As a consequence, many antifungal drugs cause side-effects. Some of these side-effects can be life-threatening if the drugs are not used properly.
- clotrimazole econazole miconazole terbinafine fluconazole ketoconazole
- This is a metabolic by-product of Penicillium griseofulvum. Griseofulvin was first isolated in 1939, but it was not until 1958 that its antifungal activity was discovered. It is produced industrially by fermenting the fungus Penicillium patulum
- It is ineffective against Candida albicans, the causative agent of oral thrush and intestinal candidasis, and against bacteria, and there is thus no disturbance of the normal bacterial flora of the gut. It is not totally absorbed when given orally, and one method of increasing absorption is to reduce the particle size of the drug.
- Griseofulvin is deposited in the deeper layers of the skin and in hair keratin, and is therefore employed in chemotherapy of fungal infections of these areas caused by susceptible organisms. Employed in chemotherapy of fungal infections of these areas caused by susceptible organisms.
- Polyene antibiotics are characterized by possessing a large ring containing a lactone group and a hydrophobic region consisting of a sequence of four to seven conjugated double bonds. Polyene antifungals bind to ergosterol, the main sterol in the fungal cell membrane, and cause depolarization of the membrane. This increases the membrane permeability and leads to cell death.
- Yeast ..common member of the human gut flora Nystatin has a specific action on C. albicans and is of no value in the treatment of any other type of infection. Poorly absorbed from the gastrointestinal tract; even after very large doses, the blood level is insignificant. They are not absorbed when given orally, so are used to treat fungal infections of the gastrointestinal tract, such as oral thrush. For treatment of systemic fungal infections they need to be administered intravenously.
- Encapsulated yeast Organic compound made by replacing the hydrogen of an acid by alkyl or other organic group. Many naturally occurring fats and essential oils are esters of fatty acids. The two forms have equal antifungal activity but higher peak serum levels are obtained with the ester. Although the ester is claimed to be less toxic, neurological effects have been observed.