Pharmacology Flashcards
Anti-fungal (Polyene)
Binds to ergosterol and forms artificial membrane pores causing leakage of intracellular ions and macromolecules from fungal cell
Very broad spectrum of action, fungicidal
Resistance due to efflux pumps
IV; available in salt and lipid formulations
Excreted slowly, can accumulate in tissues causing toxicity
Poor CNS penetration, intrathecal for meningitis
Toxicity is mostly related to binding to cholesterol in host cells
After infusion: chills, fever, muscle spasms, headache, vomiting, hypotension (reduced by slowing infusion, using antipyretics/antihistamines, and sodium loading)
Long term: renal damage is first reversible (decreased perfusion) and then irreversible (tubular injury); limit cumulative dose (not good for long term therapy)
Serious life-threatening systemic mycotic infections (broadest spectrum)
Can be used in pregnancy
Amphotericin B
Anti-fungal (Polyene)
Binds to ergosterol and forms artificial membrane pores causing leakage of intracellular ions and macromolecules from fungal cell
Very broad spectrum of action, fungicidal
Resistance due to efflux pumps
Too toxic for parenteral administration; available in creams, ointments, suppositories for application to skin and mucous membranes
Localized candida infections including oropharyngeal thrush and vaginal candida
Nystatin
Anti-fungal (azole)
Broad spectrum, resistance is more frequent because of increased clinical use of azoles (mutation of drug target)
Decrease synthesis of ergosterol by inhibiting a fungal cytochrome P450 enzyme (14-alpha-sterol demethylase)
Inhibits human P450s leading to drug interactions
Oral or IV; renal excretion
Best penetration of all the azoles into the CSF; therapeutic index is highest of the azoles
Potent inhibitor of CYP2C9 (increases serum concentration of phenytoin and warfarin)
Relatively safe with few adverse effects
Rash, Stevens-Johnson syndrome (erythema multiforme major)
Nausea, alopecia with longer treatment
Drug of choice for cryptococcal meningitis and prophylaxis in high risk patients with recurrent oral or esophageal candidiasis (resistance is a concern)
Teratogenic – contraindicated in pregnancy
Fluconazole
Anti-fungal (azole)
Broad spectrum, resistance is more frequent because of increased clinical use of azoles (mutation of drug target)
Decrease synthesis of ergosterol by inhibiting a fungal cytochrome P450 enzyme (14-alpha-sterol demethylase)
Poor CNS penetration; reduced bioavailability with rifamycins
Potent inhibitor of CYP3A4 (contraindicated with statins)
Can result in congestive heart disease
Drug of choice for dimorphic fungi Histoplasma, blastomyces and sporothrix; also effective against dermatophytes
Avoid in patients with ventricular dysfunction
Itroconazole
Anti-fungal (azole)
Broadest spectrum of the azoles, resistance is more frequent because of increased clinical use of azoles (mutation of drug target)
Decrease synthesis of ergosterol by inhibiting a fungal cytochrome P450 enzyme (14-alpha-sterol demethylase)
Oral and IV
Visual disturbances are common (blurring, changes in color vision/brightness) and occur in the first 30 min of dose and are reversible
Drug of choice for treatment of invasive aspergillosis (better outcomes and less toxicity than amphotericin B)
Voriconazole
Anti-fungal (echinocandin)
Inhibits synthesis of beta(1-3) glucan; disrupts the fungal cell wall
IV
GI discomfort, flushing, drug interactions
Hepatotoxicity (increased in combination with cyclosporine
Limited to Aspergillus and Candida
Used in invasive asperogillosis in patients not responsive to voriconazole
Contraindicated in pregnancy
Caspofungin
Anti-fungal
Derived from penicilium; fungistatic mitotic inhibitor that interferes with microtubule assembly
Administered orally in microcrystalline form
Deposited in newly growing keratin of skin and nails; treatment must persist until old infected tissue is no longer present
CNS effects, allergic syndrome similar to serum sickness, hepatotoxicity, GI disturbance P450 inducer (increased metabolism of warfarin, phenobarbital, OCPs)
Used for dermatophytosis only
Griseofulvin
Anti-fungal
Inhibits fungal squalene epoxidase which results in increased levels of squalene (toxic)
Oral
Keratophilic but also has direct fungicidal properties (potentially shorter treatment)
Generally well tolerated, no P450 drug interactions, some GI disturbance and headache
Treatment of dermatophytoses, especially onychomycosis (fingernail and toenail infections)
Contraindicated in pregnancy
Terbinafine
Anti-fungal (antimetabolite)
Taken up in fungal cells by cytosine permease, converted to 5-fluorouracil (5-FU) by cytosine deaminase; 5-FU metabolized to nucleotide that blocks DNA and RNA synthesis
Humans do not convert it to 5-fluorouracil
Oral; excreted unchanged by the liver
Converted to 5-FU in intestine by gut microflora resulting in hematotoxicity especially in renal insufficiency or AIDS
Narrow spectrum of action (only used in combinations, synergistic)
Contraindicated in pregnancy
Flucytosine
Anti-helminthic
Used for nematodes and certain cestodes/trematodes
Stage killed: eggs, larvae, adults
Mechanism of action: inhibit microtubule polymerization, inhibit energy production
Adverse effects: GI disturbances, bone marrow suppression
Resistance: switch beta-tubulin isotype, beta-tubulin point mutation
Benzimidazoles
Anti-helminthic
Used for nematodes: Onchocerciasis (in combination with steroids), lymph filariasis (in combination with benzimidazoles)
Ineffective against trematodes and cestodes
Contraindicated in loiasis
Stage killed: microfilariae
Mechanism of action: activates glutamate-gated Cl- channels, causing flaccid paralysis
Adverse effects: Mazzotti-like reaction due to dying microfilariae (use steroids)
Resistance: P-glycoprotein, mutation in channel
Ivermectin
Avermectin
Anti-helminthic
Use for nematodes: loiasis, lymph filariasis (in combination with benzimidazoles)
Contraindicated in Onchoceriasis
Stages killed: microfilariae, adults
Mechanism of action: stimulate host immune response
Adverse effects: Mazzotti-like reaction due to dying microfilariae (use steroids)
Resistance: typically not a problem
Diethylcarbamazine (DEC)
Anti-helminthic
Used for nematodes in the GI lumen
Stages killed: larvae, adults
Mechanism of action: stimulate nicotinic receptor, increases ACh release, spastic paralysis
Adverse effects: GI disturbances, headaches
Resistance: typically not a problem
Pyrantel
Anti-helminthic
Used for trematodes (schistosomiasis) and cestodes
Ineffective against nematodes
Contraindicated in intraocular cysticercosis
Stages killed: immature stages, adults
Mechanism of action: increase membrane permeability to calcium, spastic paralysis
Adverse effects: GI disturbances, headaches
Resistance: typically not a problem, mutation in VGCC?
Praziquantel
Targeted cancer drug
Metastatic colon cancer, metastatic non-small cell lung cancer
Mechanism of action: monoclonal Ab against VEGF-A to inhibit angiogenic VEGF signaling pathway
Adverse effects: hypertensive crisis, arterial thromboembolism
black box warning: GI perforations, wound healing complications, hemorrahge
Resistance/Considerations: resistance due to VEGF gene amplification
Bevacizumab
Targeted cancer drug
EGFR/ERBB1 overexpressed in metastatic colon cancer; ERBB1 overexpressed in head and neck cancer
Mechanism of action: monoclonal Ab against ERBB1 extracellular domain to prevent stimulation by EGF
Adverse effects: infusion reaction, renal failure, interstitial lung disease
Black box warning: cardiopulmonary arrest and sudden death in head and neck cancer patients
Resistance/Considerations: patients must have wild-type K-RAS prior to therapy; 50% of patients have primary resistance due to K-RAS mutation (pharmacogenetic testing)
Cetuximab
Targeted cancer drug
CML, Philadelphia chromosome positive ALL
Mechansim of action: small molecule inhibitor of intracellular kinase domain of BCR-ABL
Adverse effects:
D: myelosuppression, thrombocytopenia, QT prolongation
Resistance/Considerations:
D: greater efficacy than imitanib, used for imitanib-resistant BCR-ABL mutants with exception of T315I mutation
use P for T315I mutation
Dasatinib
Ponatinib
Targeted cancer drug
Non-small cell lung cancer (NSCLC)
Mechanism of action: small molecule inhibitor of intracellular kinase domain of EGFR
Adverse effects: serious, potentially life-threatening; interstitial lung disease, GI perforations
Resistance/Considerations: patients eligible for treatment must have exon 19 deletion mutation or L858R point mutation in ERBB1 tend to be non-responders
Acquired resistance due to T790M mutation in ERBB1 or amplification of MET oncogene leading to alternative activation of RAS-MAPK pathway
Erlotinib
Getfitnib
Targeted cancer drug
CML, Philadelphia chromosome positive ALL
Mechanism of action: small molecule inhibitor of intracellular kinase domain of BCR-ABL
Adverse effects: edema, myelosuppression, hepatotoxicity
Resistance/Considerations: acquired resistance due to up-regulation of MDR1, amplification of BCR-ABL oncogene, resistance mutations in kinase domain of BCR-ABL
Imitanib