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Antivirals and Antifungals Flashcards

1
Q

what are the oral nucleoside analogs

A

acyclovir, valacyclovir, famciclovir

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2
Q

acyclovir requires what steps

A

3 phosphorylation steps: becomes acyclovir monophosphate via viral thymidine kinase. then converts to diphosphate and triphosphate by host cell kinases like guanylate kinase. the drug requires viral kinase for initial phosphorylation, so acyclovir is selectively activated only in infected cells

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3
Q

acyclovir mechanism

A

inhibits viral DNA synthesis by competition with deoxyGTP for viral DNA polymerase, resulting in binding to DNA template as an irreversible complex. chain termination following incorporation into the viral DNA

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4
Q

valacyclovir structure

A

L-valyl ester of acyclovir

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5
Q

famciclovir structure

A

diacetyl ester prodrug of 6-deoxy penciclovir, an acyclic guanosine analog

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6
Q

what is different about penciclovir from acyclovir

A

does not cause chain termination

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7
Q

docosanol structure

A

saturated 22 carbon aliphatic alcohol

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8
Q

docosanol mechanism

A

inhibits fusion between the host cell membrane and the HSV envelope, thereby preventing entry into cells and subsequent viral replication

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9
Q

baloxavir marboxil mechanism

A

prodrug converted by hydrolysis to baloxavir, a cap-dependent endonuclease inhibitor that interferes with viral RNA transcription and blocks virus replication

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10
Q

neuraminidase inhibitors

A

oseltamivir, zanamivir

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11
Q

neuraminidase inhibitors mechanism

A

interfere with the release of progeny influenza A and B virus from infected host cells, thus halting spread. competitively and reversibly interact with the enzyme active site to inhibit viral neuraminidase activity

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12
Q

adamantanes

A

amantadine, rimantadine

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13
Q

adamantanes mechanism

A

block the M2 protein ion channel of the virus particle and inhibit uncoating of the viral RNA within infected host cells, thus preventing its replication

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14
Q

griseofulvin mechanism

A

fungistatic: interferes with fungal mitosis and nuclear acid synthesis.

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15
Q

nystatin structure

A

polyene macrolide

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16
Q

nystatin mechanism

A

binds to sterols in fungal cell membrane, changing the cell wall permeability allowing for leakage of cellular contents

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17
Q

terbinafine structure

A

synthetic allylamine

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18
Q

terbinafine mechanism

A

inhibits squalene epoxidase, a key enzyme in sterol biosynthesis in fungi. results in a deficiency in ergosterol within the fungal cell membrane and results in fungal cell death. leads to the accumulation of sterol squalene, which is toxic to the organism

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19
Q

what are the imidazoles

A

clotrimazole, miconazole, ketoconazole

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20
Q

structure of imidazoles

A

2-nitrogen azole ring

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21
Q

imidazoles mechanism

A

inhibits the CYP51 enzyme lanosterol 14-alpha-demethylase which converts lanosterol to ergosterol in fungi cellular membranes. inability to produce ergosterol increases membrane permeability, which results in cell lysis and death

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22
Q

what is ergosterol

A

the most abundant sterol in fungal cell membranes, aids in the regulation of permeability and fluidity

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23
Q

what are the triazoles

A

voriconazole, itraconazole, fluconazole, posaconazole

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24
Q

triazoles structure

A

3-nitrogen ring

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25
acyclovir activity against?
HSV1, HSV2, VSV. FAR MORE POTENT AGAINST HSV COMPARED TO VSV
26
bioavailability of acyclovir
very low, 15-20% and unaffected by food
27
elimination considerations for acyclovir
eliminated via the kidney, so reduction in dose may be necessary in reduced kidney function
28
counseling for acyclovir
take the dose with plenty of water to reduce the likelihood of acute kidney injury secondary to crystal-induced nephropathy
29
what happens to valacyclovir upon PO administration
it is rapidly converted to acyclovir via first pass enzymatic hydrolysis in the liver and intestine. results in serum levels that are 3-5x greater
30
valacyclovir bioavailability
54-70%
31
what happens to famciclovir after PO administration
it is rapidly deacetylated and oxidized by first pass metabolism to penciclovir
32
famciclovir bioavailability
70%
33
what are the instructions for docosanol
specific time: apply within 12 hours of the onset of prodromal symptoms, 5x daily
34
what does baloxavir have activity against
influenza A and B
35
half life of baloxavir
LONG, 80 hours. given as a single dose treatment initiated within 48 hours of the onset of symptoms
36
how is baloxavir metabolized
UGT1A3, minor contributions from CYP3A4
37
what is an advantage with baloxavir
it binds to a different active site than the neuraminidase inhibitors, so you can enhance activity by combining these agents. it is well tolerated.
38
counseling point for baloxavir
do not take with cation-containing products (antacids) or dairy products
39
what do the neuraminidase inhibitors have activity against
influenza A and B
40
neuraminidase inhibitors bioavailability
80%
41
elimination considerations for neuraminidase inhibitors
eliminated via the kidney, dose adjustment is necessary in patients with impaired kidney function
42
when to give neuraminidase inhibitors
early administration is crucial: influenza illness peaks at 24-72 hours after the onset of illness
43
how long is neuraminidase inhibitor course of therapy
5-days within 48h after onset of symptoms
44
how is zanamivir given
it is given via inhalation and administered directly to the respiratory tract: 10-20% reaches the lungs. Not recommended in patients with underlying airway disease
45
what do the adamantanes have activity against
influenza A only
46
dose reductions for amantadine
elderly and reduced kidney function
47
dose reductions for rimantadine
elderly, reduced kidney function, severe reduced hepatic function
48
griseofulvin absorption
Ultra-microsize almost complete absorption. Microsize 27-72%
49
counseling point for griseofulvin
take with a fatty meal: absorption is enhanced by fatty meal
50
griseofulvin adverse effects
rash: can be phototoxic/photoallergic or not. transient headaches that occur early in therapy and cease spontaneously. dizziness, mental confusion, GI upset
51
microsize dose
500 mg/day
52
ultra-microsize dose
375 mg/day
53
griseofulvin duration for ringworm
2-4wks
54
griseofulvin duration for jock itch
6 wks
55
griseofulvin duration for scalp ringworm
4-6wks
56
griseofulvin duration for athlete's foot
4-8wks
57
griseofulvin duration for onychomycosis
4-6 months
58
nystatin major PK consideration
absorption is minimal, used topically only
59
nystatin adverse effects
diarrhea, nausea, stomach pain, vomiting
60
terbinafine adverse effects
rash, d/v, dyspepsia, abdom pain, vision color confusion, decreased visual acuity, depression, taste disturbance, reversible severe neutropenia, hepatic failure, hypersensitivity, changes in ocular lens and retina, smell disturbance
61
terbinafine drug interactions
CYP2D6
62
difference in safety profile between imidazoles and triazoles?
imidazoles exhibit less selectivity for target enzyme, so greater frequency of ADRs. triazoles exhibit greater selectivity for target enzyme, thus have a better safety profile.
63
uncomplicated vaginal candidiasis
mild/moderate symptoms, sporadic, candida albicans, normal host
64
complicated vaginal candidiasis
ANY of the following: severe symptoms, recurrent, nonalbicans, abnormal host (DM, pregnant, immunosuppressed, recurrent)
65
duration for topical, vaginal candidiasis
uncomplicated: 1-3 days, complicated: 7-14 days
66
duration for systemic, vaginal candidiasis
uncomplicated: fluconazole 150 mg x 1. complicated: q72h x 2
67
vaginal candidiasis in pregnancy
use topicals
68
what defines recurrent vaginal candidiasis
4+ infections/year
69
treatment for recurrent vaginal candidiasis
fluconazole q72h x 3, then weekly x 6 months
70
options for oral candidiasis, mild
nystatin suspension 400,000-600,000 u 4x/day swish, retain, swallow. or clotrimazole troches 10 mg dissolved BID. x 7-14 days
71
options for oral candidiasis, severe
systemic: fluconazole 100 mg Day 1. 100-200 mg/day x 7-14 days (choice for immunocompromised)
72
who typically gets oral candidiasis
denture-wearers, dry mouth, antibiotics, inhaled steroids
73
topical options for onychomycosis
ciclopirox 8% or efinaconazole 10% daily x 48 weeks
74
1st line systemic option for onychomycosis
terbinafine daily x 6 weeks if fingernail or 12 weeks if toenail
75
other systemic options for onychomycosis
itraconazole, fluconazole, griseofulvin (4-6 months)
76
BCS class of griseofulvin
class II: very insoluble, high permeability
77
griseofulvin is fungi____
static
78
in addition to inhibiting fungal cell mitosis, griseofulvin binds to _____
alpha and beta tubulin to interfere with the function of spindle and cytoplasmic microtubules
79
name for body surface ringworm
tinea corporis
80
name for jock itch
tinea cruris
81
name for scalp ringworm
tinea capitis
82
name for athlete's foot
tinea pedis
83
name for onychomycosis
tinea unguium
84
besides taking griseofulvin with a high fat meal, what else should you counsel the patient
use suncreen
85
nystatin works similarly to _____
amphotericin b
86
terbinafine is largely associated with treatment of _____
onychomycosis
87
terbinafine is fungi____ and ____philic
fungicidal and keratophilic
88
what is the difference in mechanism between terbinafine and the imidazoles if they both cause ergosterol deficiency?
imidazoles interfere with the CYP51 enzyme
89
what labs to check with terbinafine
LFTs baseline and at 6 weeks
90
pros and cons of pulsed dosing with terbinafine
less effective, but reduces ADE, cost, and improves patient compliance
91
drug options when the fungal infection reaches follicles, dermis, or nails
terbinafine, itraconazole, fluconazole, griseofulvin
92
what to avoid with diaper dermatitis
topical corticosteroids with antifungal creams
93
ketoconazole drug interactions
CYP3A4 inhibitor
94
characteristics of viruses
obligate intracellular parasites, cannot replicate independent of host, must be infectious to endure, most use host cellular machinery to produce necessary components, must self-assemble, cannot make energy/proteins outside of host cell
95
components of viruses
contain RNA or DNA (not both), have a naked capsid or envelope morphology. viral components are ASSEMBLED (not replicated by cell division)
96
surface structures of the capsid or envelope are critical for interaction with the target host cell through _____
viral attachment proteins (VAPs)
97
viruses contain ______ that are crucial for entry into host cell and replication
enzymes that catalyze reactions
98
nucleocapsid characteristics
viral nucleic acid genome, protein coat serves as rigid structure, serves to package/protect/deliver during viral transmission, surrounded by lipid layer with insertions, may be contained in an envelope made of lipids/proteins/glycoproteins in aqueous conditions
99
envelope characteristics
environmentally labile, must stay in aqueous medium and cannot survive GI tract, spreads via large droplets/secretions/transfusions, does not need to kill host cell in order to spread, antibody and cell-mediated immune response often secondary to envelope, elicits hypersensitivity and inflammatory responses
100
naked capsid characteristics
environmentally stable (temp, acidic, detergents, drying), spread via fomites/hand to hand/dust/small droplets, may dry out but still infectious, ability to survive harsh acidic pH of the stomach, resistant to detergents, antibodies must be generated for immune protection
101
viruses penetrate a host cell membrane via a ______
receptor-mediated interaction
102
once the virus attaches to the host cell membrane, the viral genetic material enters the host cell and what happens
the cellular machinery of the host transcribes the viral genome, followed by translation of viral proteins
103
if RNA virus
host cell ribosomes translate RNA into protein
104
if retrovirus
RNA transcribed into DNA (reverse transcriptase) before entering viral genome
105
if DNA virus
transcription into mRNA, then translation into viral proteins
106
viral enzymes assemble material into ____ which are then released
VIRIONS
107
_____ is the complete infective form of a virus outside of a host cell
virion
108
steps of viral pathogenesis
acquisition, primary site of infection, activation of innate, incubation period, replication in target tissue, adaptive immune response, contagion, resolution or persistent/chronic infection
109
common cold/flu follows what patten of infection
acute
110
HSV follows what pattern of infection
latent
111
varicella-zoster follows that pattern of infection
chronic
112
susceptibility to viral infection and severity: the virus
viral load, genetics of virus, stability of virion in environment, replication and secretion into aerosols
113
susceptibility to viral infection and severity: the host
genetics of the host, immune status, age, overall general health, asymptomatic transmission, risk factors (travel, environment like daycare, sexual activity)
114
how is valacyclovir prodrug converted to acyclovir
first pass enzymatic hydrolysis in liver and intestine
115
in pregnant women with recurrent HSV, when is suppressive therapy recommended
36 weeks gestation
116
how is famciclovir prodrug converted to penciclovir
deacetylated and oxidized by first pass metabolism
117
influenza b viruses infect
only people
118
influenza a viruses infect
people and animals
119
neuraminidase inhibitors are analogs of ___
sialic acid

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