Antivirals 1 Flashcards
Why do drugs that block viral replication have limited effectiveness?
Because symptoms may appear late in the disease. AKA most viral particles have already been replicated. So drug won’t do much.
What is neurimidase?
A viral enzyme essential to the life cycle of the virus.
How do oseltamivir and zanamivir work?
Prevent the release of new visions.
Selective against type A and B
Do not interfere with the immune response to the influenza vaccine (will still build up a response)
Prevents infection prophylactically
Decreases intensity and duration of symptoms when given shortly after onset.
How are oseltamivir and zanamivir administers?
Oseltamivir: Oral
Zanamivir: Nasal.
They work exactly the same, but diff names for diff admins.
Side effects of oseltamivir?
GI problems.
Pro drug activated by liver.
Not much metabolism.
Side effects of zanamivir?
Bronchospasm.
Avoid in pts with asthma or COPD.
Spectrum of neurimidase inhibitors?
Influenza A and B
Spectrum of viral uncoating inhibitors?
Only influenza A. Effective for Tx and prevention. Does not impair body from building an immune response with vaccine.
Amantadine and rimantidine Spectrum Pharmacokinetics Adverse effects Resistance
- Only influenza A
- well absorbed orally
- GI, caution in pregnant people e
- Develops rapidly. Cross resistance between the two drugs, so now infrequently used.
Amantadine and rimantidine
Which one penetrates CNS?
Which one is extensively metabolized?
Amantidine.
Rimantidine is extensively processed by liver. Amantadine appears unchanged in urine.
Amantidine side effect
Penetrates CNS. May accumulate to toxic levels in pts with renal failure. Unchanged in urine.
Hepatitis types and what does an infection cause?
A, B, C, D, E. B and C are the most common, blood borne.
Replicate in and cause destruction of hepatocytes.
Interferon A
- MOA?
- Pharmacokinetics
- Adverse effects
- Mainly used for which hepatitis
- unknown
- Not active orally. Subcutaneous delivery common.
- Flu-like symptoms. Fatigue, mental depression. IFN retinopathy.
- Mainly use for B and C
IFN retinopathy
Presents as CWS and hemorrhages around the ON in the posterior pole.
3-5 months after tx.
Monitor pts on interferon therapy every 6 months.
Will improve if meds stop
5A inhibitors MOA
Interfere with RNA replication
Protease Inhibitor MOA
Prevent viral maturation of new particles.
Nucleotide/side inhibitors MOA
Insert themselves into RNA chain= termination of replication
DNA viruses
RNA viruses
Retro viruses
DNA: Herpes
RNA: Influenza, hepatitis.
Retro: HIV
Which two drugs can be used for hepatitis and HIV
Lamivudine and tenofovir
When are herpes virus meds effective?
Only during active/acute phase of the infection. Not effective during the latent phase, but can be used prophylactically.
Herpes Zoster signs/symptoms
Shingles- usually will come with dx by PCP
HA, malaise. After 1-2 days, skin starts hurting. Hot, hypersensitive, swelling 2-3 days later. Unilateral.
Can cause keratitis, corneal edema, or ant uveitis.
Make sure to dilate pt to check for vitritis and retinitis.
Ocular infections due to herpes zoster
Can cause keratitis, corneal edema, or ant uveitis.
Make sure to dilate pt to check for vitritis and retinitis.
Herpes Simplex virus (HSK)
Signs and symptoms
Causes herpetic keratitis.
Mild discomfort. Not as much pain as you would think due to nerve desensitization. Watery eyes, blurry VA, corneal ulceration and dendritic pattern.
How can herpetic keratitis be reactivated?
Fever, hormonal change, UV radiation, trauma to CN V.
Recurrance rate of HSK
10% in 1 year
23% at year 2
50% in 10 years
How can herpes zoster be reactivated?
Must have already had chicken pox.
Occurs most often in immunocompromised patients. Tb or HIV could also cause reactivation.
What to Rx for HSK?
Acyclovir orally, shed in tears (for active or prophylactically)
Triflurodine eye drop: 9x per day, except SPK
Gancyclovir (Zirgan) eye drop: 5x per day. More expensive.
Triflurodine vs gancyclovir
Both eye drops.
Trifluordine: 9x per day, expect significant SPK, cheaper.
Gancycovir (zircon) 5x per day, no SPK, expensive.
Acyclovir
Tx of choice for?
Most commonly used in tx of
Tx of choice for HSV encephalitis (rare)
Most commonly used in Tx of herpes simplex I or II.
Acyclovir MOA Pharmacokinetics Adverse effects Resistance
- Prodrug activated by viral enzyme. If no virus, then drug will pass thru system with no side effects. Could take prophylactically.
- IV, oral, or topical. No eye drop tho.Accumulates in pts with renal failure!!!!
- Local irritation with injection. HA, GI probs, renal disfunction at high doses.
- CMV is resistant (in the herpes family)
Which two drugs are clinically equivalent to acyclovir? What makes them different from acyclovir?
Valacyclovir and Famcyclovir
Val has higher oral bioavailability.
Both have longer 1/2 lives
Difference between acyclovir and valacyclovir
Val has higher oral bioavailability.
Which herpes drug is safest in pregnancy
Famcyclovir
Cidofovir
Tx for ?
Tx for CMV induced retinitis. Usually seen in pts with AIDs.
CMV induced retinitis= inflammation of NFL.
What to Rx for someone with CMV induced retinitis?
Cidofovir.
Cidofovir
Admin
MOA?
Contraindications
IV, intravitreal, topical.
Viral DNA damage. Does not depend on viral enzymes for activation.
Contraindicated in pts with pre-existing renal problems or pts taking any nephrotoxic drugs (NSAIDS)
Gancyclovir is 8-20x greater activity against ___
CMV.
Gancyclovir
Pharmacokinetics
Adverse effects
Pharmacokinetics: IV and ocular topical. High bioavailability. Accumulates in pts with renal failure. Penetrates CNS.
Dose dependent neutropenia (decrease neutrophils)
Triflurodine admin
Topical only- causes SPK.
Not given systemically bc it is too toxic.
