DR. MABANAG-ANTIFUNGAL DRUGS PART2 Flashcards
● Divided into Triazoles and Imidazoles
● Selective (Triazoles > Imidazoles) affinity (ergo,
toxicity) to fungal than human/ mammalian CY P450
enzyme
AZOLES
● Inhibition of fungal cytochrome P450 dependent Lanosterol α-demethylase ⟶ Disruption in the synthesis of Ergosterol ⟶ Damage to the cell membrane, increasing its permeability ⟶ Cell lysis and death.
AZOLES
● Many Candida spp, C. neoformans, the endemic
mycoses (blastomycosis, coccidioidomycosis, histoplasmosis), the dermatophytes. Are all susceptible.
● Aspergillus infections - Itraconazole, Posaconazole, Isavuconazole, Voriconazole, the newer Azoles.
● Tx of intrinsically AmB-resistant sp. like P. boydii
AZOLES
● Tx of intrinsically AmB-resistant sp. like P. boydii
○ Remember that AmB is inherently resistant to P. boydii, so in these cases we use Azoles.
● 1st oral azole for clinical use
● Less selective to fungal CYP450 compared to
newer Triazoles
● Greater propensity to inhibit mammalian CYP 450
Imidazoles:Ketoconazole
● Requires an acidic gastric pH for optimal absorption
○ Potent inhibitor of CYP3A4 (CYP450 enzyme 3A4)
○ potent inhibitor CY3A4 and substrate and inhibitor
for P-gp
KETOCONAZOLE
P-gp glycoprotein (P-gp) is an efflux transporter that takes drug molecules from the cell cytoplasm and transports them back into the intestinal lumen for excretion.
KETOCONAZOLE
ADVERSE REACTIONS
- LIVERTOXICITY
- GI STRESS
- PRURITUS
4.INHIBITION OF THE SYNTHESIS OF ADRENAL STEROID AND TESTOSTERONE -SPECIAL EFFECT
● Azole of choice for treatment of dimorphic fungi disease Histoplasma, Blastomyces, Sporothrix
● Activity against Aspergillus sp
● Widely used for treatment of dermatophytoses &
onychomycosis
Triazoles:Itraconazole
● DI (drug interaction): decreased bioavailability when taken w/ Rifamycins (Rifampin, Rifabutin,
Rifapentine)
● Does not affect mammalian steroid synthesis like
ketoconazole
● Less effect (vs Ketoconazole) on the metabolism
of concomitant hepatically cleared drugs
Triazoles:Itraconazole
Good CSF penetration used for fungal CNS infections
Better GI tolerance
● Kind of safe because of its widest therapeutic index
among azoles → more aggressive dosing in fungal
infections
Triazoles:Fluconazole
● Azole of choice in Tx & prophylaxis of
cryptococcal meningitis
● MC DRUG FOR mucocutaneous candidiasis
● Active vs dimorphic fungi limited to coccidioidal meningitis (remove need for intrathecal AmB)
Triazoles:Fluconazole
● Written in the clinical practice guidelines for UTI, it is the first-line antifungal for those with urinary
fungal infections.
Triazoles:Fluconazole
Clinically relevant CYP3A4 inhibitor - reduce dose
of concomitant meds: CSA, FK 506, HMG-CoA reductase inhibitors (statins)
○ There is drug interaction, in this case, when mixed with Cyclosporin A, FK 506, statins, decreasing the dose of this drug.
Triazoles:Voriconazole
Triazoles:Voriconazole
ADVERSE DRUG REACTIONS
-RASH
-INC. LIVER ENZYMES
-VISUAL DISTURBANCES (BLURRING OF VISION, VISUAL CHANGES)
-PHOTOSENSITIVITY DERMATITIS
Tx of choice for invasive aspergillosis (less toxic
than AmB) & some environmental molds (Exserohilum rostratum)
○ E. rostratum, which was called “black mold” became an epidemic in 2013 in one state in the USA, and the Tx was voriconazole.
VORICONAZOLE
● Broadest spectrum azole
● Activity vs most Candida sp & Aspergillus sp
● 1st azole with significant activity vs
mucormycosis
● Licensed for salvage treatment (Tx) in invasive resistant aspergillosis
Triazoles:Posaconazole
● Prophylaxis during leukemia induction chemotherapy, allogeneic bone marrow transplant (BMT) Pts with graft-versus-host disease
POSACONAZOLE