Presentation on theme: "Antifungal Drugs Infectious diseases caused by fungi are called mycoses, and they are often chronic in nature. Fungal infectious occur due to : 1- Abuse."— Presentation transcript:
1Antifungal DrugsInfectious diseases caused by fungi are called mycoses, and they are often chronic in nature.Fungal infectious occur due to :1- Abuse of broad spectrum antibiotics2- Decrease in the patient immunity
2They have rigid cell walls composed largely of a polymer of N-acetylglucosamine rather than peptidoglycan (a characteristic component of most bacterial cell walls).The fungal cell membrane contains ergosterol rather than the cholesterol found in mammalian membranes.These chemical characteristics are useful in targeting chemotherapeutic agents against fungal infections
3Types of fungal infections 1. Superficial : Affect skin – mucous membrane. e.g.Tinea versicolorDermatophytes : Fungi that affect keratin layer of skin, hair, nail. e.g. tinea pedis ,ring worm infectionCandidiasis : Yeast-like, oral thrush, vulvo-vaginitis , nail infections.
42- Deep infectionsAffect internal organs as : lung ,heart , brain leading to pneumonia , endocarditis , meningitis.
9Amphotericin B Amphotericin A & 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 )
10PharmacokineticsPoorly absorbed orally , 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 liverExcreted slowly in urine over a period of several days.Half-life 16 days.
11Mechanism 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 ).
13Resistance to amphotericin B If ergosterol binding is impaired either by :Decreasing the membrane concentration of ergosterol.Or by modifying the sterol target molecule.
14Adverse Effects 1- Immediate reactions (Infusion –related toxicity). Fever, muscle spasm, vomiting, headache, hypotension.Can be avoided by:A. Slowing the infusionB. Decreasing the daily doseC.Premedication with antipyretics, antihistamincs or corticosteroids.D. A test dose.
152- Slower toxicityMost serious is renal toxicity (nearly in all patients ).HypokalemiaHypomagnesaemiaImpaired liver functionsThrombocytopeniaAnemia
16Clinical uses Has a broad spectrum of activity & fungicidal action. The drug of choice for life-threatening mycotic infections.For induction regimen for serious fungal infection.Also, for chronic therapy & preventive therapy of relapse.In cancer patients with neutropenia who remain febrile on broad –spectrum antibiotics.
17Routes of Administration 1- Slow I.V.I. For systemic fungal disease.2- Intrathecal for fungal C.N.S. infections.3- Topical drops & direct subconjunctival injection for Mycotic corneal ulcers & keratitis.3- Local injection into the joint in fungal arthritis.4- Bladder irrigation in Candiduria.
18Liposomal preparations of amphotericin B Amphotericin B is packaged in a lipid- associated delivery system to reduce binding to human cell membrane , so reducing :A. NephrotoxicityB. Infusion toxicityAlso, more effectiveMore expensive
20NystatinIt is a polyene macrolide ,similar in structure & mechanism to amphotericin B.Too toxic for systemic use.Used only topically.It is available as creams, ointment , suppositories & other preparations.Not significantly absorbed from skin, mucous membrane, GIT .
21Clinical usesPrevent or treat superficial candidiasis of mouth, esophagus, intestinal tract.Vaginal candidiasisCan be used in combination with antibacterial agents & corticosteroids.
22AzolesA group of synthetic fungistatic agents with a broad spectrum of activity .They have antibacterial , antiprotozoal anthelminthic & antifungal activity .
23Mechanism of Action1-Inhibit the 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.
24AzolesThey are classified into :Imidazole groupTriazole group
25Imidazoles 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.
26Ketoconazole Well absorbed orally . 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).
27Ketoconazole (cont.)Inactivated in liver & excreted in bile (feces ) & urine.Does not cross BBB.
28Clinical usesUsed topically or systematic (oral route only ) to treat :1- Oral & vaginal candidiasis.2- Dermatophytosis.3- Systemic mycoses.
29Adverse Effects Nausea, vomiting ,anorexia Hepatotoxic Inhibits human P 450 enzymesInhibits adrenal & gonadal steroids leading to:Menstrual irregularitiesLoss of libidoImpotenceGynaecomastia in males
30Contraindications & Drug interactions Contraindicated in :Prgnancy, lactation ,hepatic dysfunctionInteract with enzyme inhibitors , enzyme inducers.H2 blockers & antacids decrease its absorption
32Triazoles Fluconazole Itraconazole Voriconazole They are : Selective Resistant to degradationCausing less endocrine disturbance
33Itraconazole Lacks endocrine side effects Has a broad spectrum activityGiven orally & IVFood increases its absorptionMetabolized in liver to active metaboliteHighly lipid soluble ,well distributed to bone, sputum ,adipose tissues.Can not cross BBB
34Itraconazole (cont.) Half-life 30-40 hours Used orally in dermatophytosis & vulvo-vaginal candidiasis.IV only in serious infections.Effective in AIDS-associated histoplasmosisSide effects :Nausea, vomiting, hypokalemia, hypertension, edema, inhibits the metabolism of many drugs as oral anticoagulants.
35Fluconazole Water soluble Completely absorbed from GIT Excellent bioavailability after oral administrationBioavailability is not affected by food or gastric PHConcentrated in plasma is same by oral or IV routeHas the least effect on hepatic microsomal enzymes
36Fluconazole (cont.) Drug interactions are less common Penetrates well BBB so, it is the drug of choice of cryptococcal meningitisSafely given in patients receiving bone marrow transplants (reducing fungal infections)Excreted mainly through kidneyHalf-life hoursResistance is not a problem
37Clinical uses Candidiasis ( is effective in all forms of mucocutaneous candidiasis)Cryptococcus meningitisHistoplasmosis, blastomycosis, , ring worm.Not effective in aspergillosis
38Side effectsNausea, vomiting, headache, skin rash , diarrhea, abdominal pain , reversible alopecia.Hepatic failure may lead to deathHighly teratogenic ( as other azoles)Inhibit P450 cytochromeNo endocrine side effects
39Voriconazole A broad spectrum antifungal agent Given orally or IV High oral bioavailabilityPenetrates tissues well including CSFInhibit P450Used for the treatment of invasive aspergillosis & serious infections.Reversible visual disturbances
40FlucytosineSynthetic pyrimidine antimetabolite (cytotoxic drug ) often given in combination with amphotericin B & itraconazole.Systemic fungistatic
41Mechanism of actionConverted within the fungal cell to 5- fluorouracil (Not in human cell ), that inhibits thymidylate synthetase enzyme that inhibits DNA synthesis.(Amphotericin B increases cell permeability , allowing more 5-FC to penetrate the cell, they are synergistic).
42Phrmacokinetics Rapidly & well absorbed orally Widely distributed including CSF.Mainly excreted unchanged through kidneyHalf-life 3-6 hours
43Clinical uses Severe deep fungal infections as in meningitis Generally given with amphotericin BFor cryptococcal meningitis in AIDS patients
44Adverse Effects Nausea, vomiting , diarrhea, severe enterocolitis Reversible neutropenia, thrombocytopenia, bone marrow depressionAlopeciaElevation in hepatic enzymes
45CaspofunginInhibits the synthesis of fungal cell wall by inhibiting the synthesis of β(1,3)-D-glucan, leading to lysis & cell death.Given by IV route onlyHighly bound to plasma proteinsHalf-life 9-11 hoursSlowly metabolized by hydrolysis & N-acetylation.Elimination is nearly equal between the urinary & fecal routes.
46Clinical uses Effective in aspergillus & candida infections. Second line for those who have failed or cannot tolerate amphotericin B or itraconazole.Adverse effects :Nausea, vomitingFlushing (release of histamine from mast cells)Very expensive
47Griseofulvin Fungistatic, has a narrow spectrum Given orally (Absorption increases with fatty meal )Half-life 26 hoursTaken selectively by newly formed skin & concentrated in the keratin.Induces cytochrome P450 enzymesShould be given for 2-6weeks for skin & hair infections to allow replacement of infected keratin by the resistant structure
48Griseofulvin(cont.)Inhibits fungal mitosis by interfering with microtubule functionUsed to treat dermatophyte infections ( ring worm of skin, hair, nails ).Highly effective in athlete,s foot.Ineffective topically.Not effective in subcutaneous or deep mycosis.Adverse effects ;Peripheral neuritis, mental confusion, fatigue, vertigo, GIT upset, enzyme inducer, blurred vision.Increases alcohol intoxication.
49TOLNAFTATE Effective in most cutaneous mycosis. Ineffective against Candida.Used in tinea pedis ( cure rate 80% ).Used as cream, gel, powder, topical solution.Applied twice daily.
50NAFTIFINE Broad spectrum fungicidal . Available as cream or gel. Effective for treatment of tinea cruris.
51TERBINAFINE Drug of choice for treating dermatophytes (onychomycoses). Better tolerated ,needs shorter duration of therapy.Inhibits fungal squalene epoxidase, decreasesThe synthesis of ergosterol .(Accumulation of squalene ,which is toxic to the organism causing death of fungal cell).
52Fungicidal ,its activity is limited to candida albicans & dermatophytes. Effective for treatment of onychomycoses6 weeks for finger nail infection & 12 weeks for toe nail infections .Well absorbed orally , bioavailability decreases due to first pass metabolism in liver.
53Highly protein binding Accumulates in skin , nails, fat.Severely hepatotoxic, liver failure even death.Accumulate in breast milk , should not be given to nursing mother.GIT upset (diarrhea, dyspepsia, nausea )Taste & visual disturbance.