Antivirals, Antifungals & Antiprotozoans Flashcards
antiviral agents are designed to do what?
inhibit viral replication or proliferation
enveloped or non-enveloped:
can stay on surfaces longer without the fear of drying out
nonenveloped
enveloped or nonenveloped:
can be killed with alcohol, hydrogen peroxide, chlorine, etc.
enveloped
what are some examples of enveloped viruses?
- herpesvirus
- retrovirus
- coronavirus
what are some examples of nonenveloped viruses?
adenovirus & parvovirus
what virus is a cold virus that is the most common cause of eye infections? what kind of eye infections does it cause?
adenovirus → highly infectious conjunctivitis and/or keratitis
which serotype of adenovirus is the most common cause of epidemic keratoconjunctivitis (EKC)?
adenovirus 8
what is the incubation period of adenovirus 8?
~8 days
on days 8-16, what signs appear in an adenovirus 8 infection?
conjunctivitis & fine SPK
in an adenovirus 8 infection, what appears on day 8?
focal epithelial keratitis
in an adenovirus 8 infection, 8 days after day 8, what sign(s) appears?
subepithelial infiltrates
what is the treatment for EKC?
no FDA-approved treatment → normally self-resolving
- palliative care & good hygiene
what are some clinical findings in EKC?
follicles, palpable PA node, pseudomembranes
what treatment is not FDA approved, but can be used to treat EKC?
Betadine protocol (povidone-iodine)
which virus is the most common virus of the human body & why?
herpesvirus → resides in nerve ganglia for life
purines or pyrimidines?
two-carbon nitrogen ring bases used to produce DNA/RNA nucleotides adenine & guanine
purines
purines or pyrimidines?
one-carbon nitrogen ring bases that are used to produce DNA/RNA nucleotides thymine/uracil & cytosine
pyrimidines
what antiviral agents are commonly used to treat herpes (simplex & keratitis)?
purine & pyrimidine analogs
trifluridine (Viroptic) 1% topical solution is what type of antiviral agent?
pyrimidine analog
what is trifluridine uniquely preserved with?
thimerosal 0.001%
what is the treatment regimen for herpesvirus with trifluridine 1% (Viroptic)?
1 gtt q2h until re-epithelialized → 1gtt q4h x 7 additional days
what is the maximum recommended use for trifluridine 1% & why?
21 days because it is very destructive to the cornea
what kind of antiviral agent is ganciclovir?
purine analog
what is the treatment regimen with ganciclovir 0.15% (Zirgan) for HSV keratitis?
1gtt 5x/day until healing → 1gtt TID x 7d (or it can come back)
why is ganciclovir preferred over trifluridine for HSV keratitis?
less corneal toxicity
ganciclovir has cross-resistance with which antiviral agent?
acyclovir
what class of antiviral agents is acyclovir?
purine analog
what is the therapy regimen for HSK with acyclovir?
400mg PO 5x/d x 7d
what is the therapy regimen for HZK with acyclovir?
800mg PO 5x/day x 7-10 days
when is it most important to treat HZK & why?
the first 72 hours to prevent postherpetic neuralgia
out of all the purine analogs, which has the poorest GI absorption?
acyclovir
which antiviral agent is a prodrug of acyclovir & what class is it?
valacyclovir → purine analog
what is the therapy regimen for HSK with valacyclovir?
500mg PO TID x 7-10d
what is the therapy regimen for HZK with valacyclovir?
1000mg PO TID x 7-10d
valacyclovir has cross-sensitivity with which antiviral agent?
acyclovir
which antiviral agent is better suited for deeper infections such as stromal keratitis?
valacyclovir
which antiviral agent is a penciclovir prodrug with extended plasma life? what class is it?
famciclovir → purine analog
what is the therapy regimen for HSK with famciclovir?
250mg TID x 7-10d
what is the therapy regimen for HZK with famciclovir?
500 mg TID x 7-10d
when someone is allergic to acyclovir or valacyclovir, what antiviral agent can they use?
famciclovir
what are the ocular sequelae of viral infections?
blepharitis, conjunctivitis, epithelial & stromal keratitis, uveitis, retinitis, acute retinal necrosis (in severe cases)
what are the two types of fungi that can cause fungal infections
- budding unicellular yeasts
- branching filamentous molds
what ocular structures are involved in fungal infections?
cornea, conjunctiva, lens, ciliary body, vitreous body, uvea
what are the two types of yeast that can cause ocular involvement in an infection?
candida, cryptococcus
what are the three types of molds that can cause ocular involvement in an infection?
aspergillus, fusarium, curvularia
what can enhance the risk of a fungal infection?
- CL wear
- steroids
- trauma (including LASIK)
- immunocompromised
which class of antifungals work by increase membrane permeability?
polyenes
what are the two polyenes & what do they treat?
- amphotericin B (yeasts = nonfilamentous)
- natamycin (mold = filamentous)
which polyene is the only FDA approved topical?
natamycin
are there any adverse reactions with polyenes?
amphotericin B can cause renal toxicity (esp. with IV)
what class of antifungals inhibits DNA synthesis?
pyrimidines
name a drug that is a pyrimidine, & what is its MOA?
flucytosine → inhibits thymidine synthesis
is flucytosine fungistatic or fungicidal?
fungistatic
what are the adverse reactions of flucytosine?
bone marrow toxicity & hepatotoxicity
what class of antifungals inihibit protein synthesis? what is their MOA?
azoles → impair ergosterol synthesis & inhibit some cytochrome P450 enzymes which may reduce metabolism of other drugs
what class of antifungals are these?
- ketoconazole
- fluconazole
- posaconazole
- voriconazole
- itraconazole
- miconazole
azoles
which two azoles can cause hepatotoxicity?
ketoconazole & fluconazole
what class of antifungals are cell wall inhibitors? what is their MOA?
echinocandins → inhibit glucan synthese which weakens cell walls
what are some echinocandins?
casofungin, micafungin, anidulafungin
why do echinocandins have less risk of hepatotoxicity?
because they are not metabolized by the liver
which classes of antifungals have developing resistance?
pyrimidines & azoles
what is one of the most common soil or waterborne protozoa?
acanthamoeba
which organism is responsible for the most virulent form of infectious keratitis & has the worst prognosis? what type of organism is it?
acanthamoeba - protozoa
most acanthamoeba keratitis cases are caused by what?
CL wear > trauma
what medical therapy can be used to for acanthamoeba infections? give some examples
topical biguanides qh-q3h x 3-4wks
- polyhexamethylene biguanide 0.02% (PHMB)
- bisbiguanide 0.02% (chlorhexidine)
what has similar presentation as an acanthamoeba infection?
topical anesthetic abuse syndrome
what protozoal infection comes from poorly cooked food, unwashed vegetables, exposure to cat feces?
toxoplasmosis gondii infection
- sulfadiazine + pyrimethamine (Sulfadoxine)
- sulfamethoxazole + trimethoprim (Bactrim)
- clindamycin
- spiramycin
these are all used to treat what?
acute toxoplasmosis infections
what can you use to treat latent toxoplasmosis infections?
atovaquone & clindamycin