Course content Chemotherapeutic agents Mechanism of actions 5/8/2018 Chemotherapeutic agents Mechanism of actions Indications Contraindications/Cautions Drug interactions Side-effects/Adverse reactions Dosage regimen (occasionally) C.Agyare

Reference Books Pharmacology by Rang, Dale, Ritter, Gardner 5/8/2018 Pharmacology by Rang, Dale, Ritter, Gardner Clinical Pharmacology textbooks British National Formulary (BNF) C.Agyare

Antifungal agents 5/8/2018 C.Agyare

Most fungi are commensals or live in the environment. But increasing incidence and severity of human fungal infections Fungal infections are termed mycoses and in Generally can be divided into: 1) Superficial infections 2) Cutaneous infections 3) Sub-cutaneous infections 4) Systemic infections 5/8/2018 C.Agyare

FUNGAL INFECTIONS blastomycosis candidiasis histoplasmosis 5/8/2018 C.Agyare blastomycosis candidiasis histoplasmosis mucorymycosis ringworm

Factors increasing incidence and severity of human fungal infections Widespread use of broad-spectrum antibiotics (antimicrobial drugs) Reduced immune responses caused by AIDS Use of immunosuppressant drugs Administration of anticancer drugs (cancer chemotherapy) Chronic use of steroids (spreading of an infection) 5/8/2018 C.Agyare

FUNGAL INFECTIONS Fungal infections are usually more difficult to treat than bacterial infections Fungal organisms grow slowly Fungal infections often occur in tissues that are poorly penetrated by antimicrobial agents Eg: devitalized or avascular tissues . 5/8/2018 C.Agyare

ANTIFUNGAL AGENTS The Azoles Griseofulvin Flucytosine The polyenes 5/8/2018 The Azoles Griseofulvin Flucytosine The polyenes Echinocandin antifungals (new) C.Agyare

Antifungals damaging permeability of the cell membrane Imidazoles: Bifonazole, Clotrimazole, Econazole, Ketoconazole, Miconazole Triazoles: Fluconazole, Itraconazole, Voriconazole Allylamines: Terbinafine, Naftifine Morpholines: Amorolfine Thiocarbamates: Tolciclate, Tolnaftate Substituted pyridones: Ciclopirox Polyene antibiotics: Amphotericin B, Nystatin 5/8/2018 C.Agyare

II. Antifungals inhibiting cell wall synthesis Echinocandins: Caspofungin, anidulafungin and micafungin III. Antifungals inhibiting synthesis of nucleic acids Flucytosine Griseofulvin????? 5/8/2018 C.Agyare

5/8/2018 C.Agyare

AZOLES Comprise the imidazoles and triazoles 5/8/2018 C.Agyare

Miconazole Bifonazole Ketoconazole Butoconazole Clotrimazole Econazole Imidazoles: Miconazole Bifonazole Ketoconazole Butoconazole Clotrimazole Econazole Fenticonazole Tioconazole Isoconazole Oxiconazole Sertaconazole Sulconazole Triazoles: Fluconazole Itraconazole Ravuconazole Posaconazole Voriconazole 5/8/2018 C.Agyare

Mechanism of action Azoles inhibit the enzyme cytochrome P450 14α- demethylase. This enzyme converts lanosterol to ergosterol, and is required in fungal cell membrane synthesis 5/8/2018 C.Agyare

Azoles Reduced fungal membrane ergosterol concentrations result in damaged, leaky cell membranes Azoles inhibiting cytochrome P450 enzymes (inhibits biosynthesis of adrenal and gonadal steroid hormones) The toxicity of these drugs depends on their relative affinities for mammalian and fungal cytochrome P450 enzymes. The triazoles tend to have fewer side effects, better absorption, better drug distribution in body tissues, and fewer drug interactions. 5/8/2018 C.Agyare

KETOCONAZOLE Spectrum of activity includes ٭ Candida species ٭ Coccidioides immitis ٭ Cryptococcus neoformans * Dermatophytes & Pityriasis versicolor 5/8/2018 C.Agyare

Pharmacokinetics An acid environment is necessary for ketoconazole absorption Administration of food with ketoconazole appears to increase absorption due possibly to: 1) increased bile secretions 2) delayed gastric emptying Does not cross the intact blood-brain barrier except in meningitis. Urinary concentrations of ketoconazole are usually low, but vaginal and vaginal tissue concentrations correlate with those in serum. 5/8/2018 C.Agyare

KETOCONAZOLE Metabolized through oxidation, dealkylation, aromatic hydroxylation. Excreted into the bile, faeces and the urine Bile Faeces Urine 5/8/2018 C.Agyare

Side effects Impotence Gynaecomastia Reduced sperm count Decreased libido Hepatotoxicity Nausea/vomiting Pruritis Dizziness Photophobia 5/8/2018 C.Agyare

Contraindications/Precautions Achlorhydria Hypochlorhydria Alcoholism Breast-feeding Children Hepatic disease Pregnancy 5/8/2018 C.Agyare

Drug interactions Antacids H2 blockers Omeprazole Isoniazid Corticosteroids Ethanol Phenytoin Rifampicin Astemizole Amphotericin B 5/8/2018 C.Agyare

Miconazole, Econazole, Clotrimazole Bioavailability is low when administered orally Usually used topically. 5/8/2018 C.Agyare

Fluconazole Does not require an acidic environment, as does ketoconazole, for GI absorption. About 80 to 90% absorbed from GIT. Thet1/2 of the drug is 27 to 37 h, permitting once-daily dosing in patients with normal renal function. Only 11% of the circulating drug is bound to plasma proteins. 5/8/2018 C.Agyare

Fluconazole The drug penetrates widely into most body tissues eg CSF therefore effective for treating fungal meningitis. About 80% of the drug is excreted unchanged in the urine. Dosage reductions are required in the presence of renal insufficiency. Alopecia and hepatic necrosis have been reported as adverse effects 5/8/2018 C.Agyare

Itraconazole Lipophilic and water insoluble Requires a low gastric pH for absorption. Oral bioavailability is variable (20 to 60%). It is highly protein bound (99%) Metabolized in the liver and excreted into the bile. Useful in the treatment of disseminated histoplasmosis in AIDS, nonmeningeal blastomycosis and sporotrichosis 5/8/2018 C.Agyare

Itraconazole Contraindicated in conditions of hepatic and renal impairment, pregnancy and breastfeeding mothers Side effects include nausea, abdominal pain and rash. Flatulence, constipation, menstrual disorders and alopecia may occur. 5/8/2018 C.Agyare

GRISEOFULVIN Fermentation product of Penicillium griseofulvum Mode of action not exactly understood but involves nucleic acid synthesis and cell mitosis Dermatophyte infections of the skin, scalp, hair and nails Infections where susceptible strains of Trichophyton, Microsporum and Epidermaphyte are implicated. Griseofulvin also is deposited in keratin cells on the surface of the skin making it difficult for fungus to invade the skin and other tissues 5/8/2018 C.Agyare

Pharmacokinetics Well absorbed after oral administration. Presence of fat in the diet appears increase absorption of griseofulvin Metabolized in the liver and then excreted in urine 5/8/2018 C.Agyare

Drug Interactions Barbiturates ( e.g. Phenobarbitone) Warfarin Oestrogen Progesterone preparations 5/8/2018 C.Agyare

Toxicity and Side Effects Headache Abdominal discomfort Rashes Fatigue, Dizziness (enhance effect of alcohol) Confusion and impaired co-ordination 5/8/2018 C.Agyare

POLYENE ANTIFUNGALS Amphotericin B Mechanism of Action: Destroys the integrity of cellular membrane of susceptible organism by binding to ergosterol Active against most fungi and yeast Treatment of systemic fungal infections. Not absorbed from the gut Given by IV infusion 5/8/2018 C.Agyare

5/8/2018 C.Agyare

Toxic Effects Anorexia, Nausea, Vomiting, diarrhoea, epigastric pain 5/8/2018 Anorexia, Nausea, Vomiting, diarrhoea, epigastric pain Headache, Muscle and Joint pain Disturbances in renal and liver functions Neurological and blood disorders C.Agyare

Clinical Uses Drug of choice in most systemic mycoses Candidiasis Cryptococcosis Aspergillosis Mucormycosis. 5/8/2018 C.Agyare

Nystatin Produced from Streptomyces noursei Active against Candida albicans infections of skin and mucous membranes Not absorbed when given by mouth Its activity is affected by long exposure to light, and heat 5/8/2018 C.Agyare

Side Effects Nausea Vomiting and Diarrhoea (at high doses) Oral irritation Rashes (topical and vaginal forms) 5/8/2018 C.Agyare

Flucytosine (5-flucytosine, 5-FC) Fluorinated purimidine related to fluouracil and floxuridine An analogue of cytosine that was originally synthesized for possible use as an antineoplastic agent. 5-FC is converted to 5-fluorouracil inside the cell by the fungal enzyme cytosine deaminase. The active metabolite 5-fluorouracil interferes with fungal DNA synthesis by inhibiting thymidylate synthetase. Incorporation of these metabolites into fungal RNA inhibits protein synthesis. Indicated for :Crytococcus neoformans (Crytococcal), Candida infections (UTI’s) and Torulopsis glabrata 5/8/2018 C.Agyare

5/8/2018 C.Agyare

Pharmacokinetics Rapidly and well absorbed in GI tract Widely distributed in the body Minimally bound to proteins Approximately 80% excreted in the urine (unchanged) Half-life 3-6 hours 5/8/2018 C.Agyare

Side Effects Leukopenia Thrombocytopenia Rash Nausea and vomiting diarrhoea. Severe enterocolitis Confusion, headache, sedation 5/8/2018 C.Agyare

Drug Interactions 5/8/2018 Amphotericin Cytotoxics C.Agyare

Allylamines Reversible noncompetitive inhibitors of the fungal enzyme squalene epoxidase, which converts squalene to lanosterol. These agents exhibit fungicidal activity against dermatophytesand fungistatic activity against yeasts. Naftifine is available for topical use only in the treatment of cutaneous dermatophyte and Candida infections. 5/8/2018 C.Agyare

5/8/2018 C.Agyare

Terbinafine Dermatophyte infections of the nails and ringworm infections Available for topical and systemic use Lipophilic and highly binds to plasma protiens Cautions Hepatic and renal impairment Pregnancy Breast feeding 5/8/2018 C.Agyare

Drug interactions 5/8/2018 Rifampicin Cimetidine Famotidine C.Agyare

Side effects Abdominal discomfort Anorexia Urticaria rash 5/8/2018 Abdominal discomfort Anorexia Urticaria rash Taste disturbance Photosensitivity C.Agyare

ECHINOCANDIN ANTIFUNGALS Mode of action: inhibit ß-(1,3) glucan synthesis, damaging fungal cell walls no drug target in mammalian cells Rapidly fungicidal against most Candida spp. Fungistatic against Aspergillus spp. Active against cyst form of Pneumocystis carinii. 5/8/2018 C.Agyare

5/8/2018 C.Agyare

Caspofungin Pharmacokinetics Administration: IV 96% plasma protein bound Predominantly hepatic metabolism (hydrolysis and N-acetylation). Distribution: urinary concentration low, CSF concentration expected to be low 5/8/2018 C.Agyare

Adverse effects Fever Hepatotoxicity Headache Phlebitis raised transaminases common in patients receiving caspofungin hepatic necrosis in animals given large doses (5-8 mg/kg) Headache Phlebitis Rash (infrequent) Haemolysis may occur but clinically significant haemolysis is rare 5/8/2018 C.Agyare

Drug interactions Slight increases in clearance with co- adminstration of: phenytoin carbamazepine dexamethasone efavirenz, nelfinavir, nevirapine Rifampicin - concentrations of both drugs increased Tacrolimus - concentration of tacrolimus decreased by ~20% Cyclosporin - increased caspofungin plasma concentration 5/8/2018 C.Agyare

Micafungin Pharmacokinetics Administration: IV 99.8% plasma protein bound Predominantly hepatic metabolism (hydrolysis and N-acetylation). Hepatic uptake slow, leading to long terminal half-life of 11-17 h also adrenal and splenic metabolism cannot be dialysed Distribution: urinary concentration low, CSF concentration is low 5/8/2018 C.Agyare

Clinical use Drug interactions Invasive aspergillosis 5/8/2018 Invasive aspergillosis Drug interactions No interactions reported C.Agyare

Adverse effects Phlebitis Abnormal liver function tests 5/8/2018 Phlebitis Abnormal liver function tests Rash (infrequent ) Headache Fever uncommon Clinically significant haemolysis rare C.Agyare

Pyridones Ciclopirox olamine is a pyridone derivative Use for the treatment of cutaneous dermatophyte infections, cutaneous C. albicans infections and tinea versicolor caused by Malassezia furfur. Mode of action: It interferes with fungal growth by inhibiting macromolecule synthesis (blocks amino acid synthesis) 5/8/2018 C.Agyare

Thiocarbamates Tolnaftate effective in the treatment of dermatophyte infections and tinea. Mechanism of action : not clear however, it is believed to inhibit squalene epoxidase, 5/8/2018 C.Agyare

Haloprogin Haloprogin is a halogenated phenolic ether administered topically for dermotaphytic (tinea)infections. Mechanism of action is unknown, but it is thought to be via inhibition of oxygen uptake and disruption of yeast membrane structure and function 5/8/2018 C.Agyare

Thanks for your attention 5/8/2018 C.Agyare