Exam 3: Antivirals Flashcards
Describe the mechanisms of Antivirals
- Alter uncaring of virus
- virus uncoats to begin replication
- drugs prohibit this phase, so cannot penetrate host
- Polymerase inhibitors
- Inhibit viral protein synthesis
What antiviral drugs are indicated for Influenza A?
amantadine (Symmetril)
rimantidine (Flumadine)
Mechanism of amantadine and rimantidine
Blocks uncaring of virus preventing penetration into host
- rimantidine is significantly more active than amantadine
Side effects of amantadine and rimantidine
- CNS stimulation
- enhanced by antihistamines and caffeine
- Insomnia
- Grand Mal Seizures
Indications for Tamiflu
Influenza A or B
What drug is considered the classic prodrug?
Tamiflu
- hydrolyzed to active form
Action of Tamiflu
Neuraminidase inhibitor
- drug is an enzyme inhibitor that cleaves the budding viral progeny from its cellular envelope attachment point just prior to release
Indications for ribavirin (Rebetol, Virazole)
Treatment of respiratory syncytial virus
Mechanism of ribavirin
prevents synthesis of viral proteins encoded by viral mRNA
- inhibits virus RNA polymerase
- Disrupts transcription, translation or promotes degradation of viral RNA
Side effects of ribavirin
mutagenic
teratogenic
carcinogenic
Indications for trifluridine (Viroptic)
herpes simplex keratitis (in eye)
keratoconjunctivitis
Mechanism of trifluridine
interferes with viral replication by incorporating into viral DNA in place of thymidine, causing formation of defective proteins
What is the IV drug of choice for HSV encephalitis?
acyclovir (Zovirax)
Action of acyclovir (Zovirax)
Inhibits viral DNA polymerase preferentially (Cell cycle specific)
Indications for acyclovir
IV drug of choice for HSV encephalitis
- primary and recurrent herpes in immunocompromised patients
How often does acyclovir need to be used?
Every 3 hours, which is consistent with cycle phases of viruses
Indication of ganciclovir (Cytovene)
human cytomegalovirus (CMV) - treats CMV retinitis
Action of ganciclovir (Cytosine)
inhibits viral DNA synthesis
Which drugs are indicated to treat recurrent genital herpes
famciclovir and valacyclovir
T or F, famciclovir and valacyclovir are classic prodrugs
true
What are interferons?
a family of naturally occurring, inducible glycoproteins that interfere with the ability of viruses to infect cells
- antiviral, cytotoxic, immunomodulatory actions
3 types of interferons?
alpha
beta
gamma
How are interferons administered?
intralesionally
subcutaneously
IV
Mechanism of Interferons
Not completely understood…
- Induction of host cell enzymes that inhibit viral RNA translation, ultimately leading to the degradation of viral mRNA and tRNA
Most common indications of Inteferons
Hepatitis B and C
Multiple Sclerosis
- Also used for some cancers
Adverse effects of Inteferons
- Flu-like symptoms
- bone marrow suppression
- neurotoxicity
- CNS effects
- Severe fatigue
- Severe weight loss
- Autoimmune disorders
- Cardiovascular
- Oral
Name the new drugs for Hepatitis C
- ledipasvir + sofosbuvir (Harvoni)
- simeprevir (Olysio)
- sofosbuvir (Sovaldi)
- boceprevir (Victrelis)
- telaprevir (Incivek)
What is the challenge with antiretrovirals
To kill the virus, host cells are often harmed
- Antivirals that alter viral replication processes are often toxic to host cells
Explain the mechanism of Antiretrovirals
- Inhibiting viral attachment and entry limits spread of virus within body
- Alter genome replication = polymerase inhibitors
- Immunization = provides antibodies against viral envelop proteins
Name the drug that was the first antiviral HIV agent that inhibits viral entry into host cells
enfuvirtide (Fuzeon)
Target of antiretrovirals for Retrovirsuses?
Reverse transcriptase (1st class to be used) - main enzyme used by virus to copy genome into DNA
3 primary classes of Antiretroviral drugs for HIV
- Nucleoside reverse transcriptase inhibitors
- Protease inhibitors
- Nonnucleoside reverse transcriptase inhibitors
What are the drug concepts for HIV?
- Drugs target structural and functional differences between viral and human proteins
- Treatment of HIV infection requires combination therapy = HAART (Highly Active AntiRetroviral Therapy)
- “cocktails”
Define a typical cocktail
all of the primary classes of antiretroviral drugs
- nucleoside reverse transcriptase inhibitor
- non-nucleoside reverse transcriptase
- protease inhibitors
When are antiretrovirals started in a patient?
when immunosuppression becomes pronounced
- CD4
What is a Triple Cocktail?
2 nucleoside reverse transcriptase inhibitors
1 Protease inhibitor
Side effects of Antiretrovirals
- Anemia (toxic to bone marrow and blood cells)
- Leukopenia and granulocytopenia
- Hepatotoxicity
- Peripheral neuropathy
- Pancreatitis
T or F, Nucleoside Reverse transcriptase inhibitors are not classified as prodrugs
False,
Must be biotransformed/bioactivated to work
Action of Nucleoside Reverse transcriptase inhibitors
Drug is integrated into DNA polymerase so that synthesis of viral DNA is terminated
- Inhibits viral enzyme reverse transcriptase
- **Drugs have no effect on cells already containing HIV
T or F, Reverse transcriptase of HIV is 1100 times less susceptible to inhibition than are normal human cells making them harder to target
False,
1100 times more susceptible
List the Nucleoside reverse transcriptase inhibitors
abacavir (Ziagen) (B) didanosine (Videx) emtricitabine (Emtriva) lamivudine (Epivir) stavudine (Zerit) zalcitabine (Hivid) (B) zidovudine (Retrovir) = AZT
Action of AZT
Inhibits HIV synthesis and reduces morbidity/mortality from AIDS and AIDS-related complex
Side effects of AZT
- Very toxic = bone marrow depression
- CNS effects
- Nausea
- Oral effects = altered taste, tongue edema, bleeding gingiva
What drugs have interactions that inhibit metabolism of AZT
NSAIDS
Aspirin
List the Non-nucleoside reverse transcriptase inhibitors
delavirdine (Rescriptor)
efavirenz (Sustiva)
etravirine (Intelence)
nevirapine (Viramune)
Action of Non-nucleoside reverse transcriptase inhibitors
block reverse transcriptase
- Drugs inhibit the catalytic reaction of reverse transcriptase that is independent of nucleotide binding
T or F, Non-nucleoside reverse transcriptase inhibitors are classified as prodrugs
false, Do not require bioactivation
Action of Protease Inhibitors
Drugs suppress viral replication by inhibiting protease, the enzyme responsible for cleaving viral precursor peptides into infective virions
- Prevents maturation of HIV-infected cells
What is the primary difference of protease inhibitors vs the other 2 classes of antiretrovirals
Interfere with the action of HIV-infected cells
List the Protease inhibitors
atazanavir (Reyataz) darunavir (Prezista) fosamprenavir (Lexiva) (B) indinavir (Crixivan) (B) nelfinavir (Viracept) ritonavir (Norvit) (B) saquinavir (Invirase) tipranavir (Aptivus)
Action of Nucleotide Reverse transcriptase inhibitors
Interferes with HIV viral RNA dependent DNA polymerase resulting in inhibition of viral replication
Name the Nucleotide Reverse Transcriptase inhibitor drug
tenofovir (Viread)
Action of Integrase Inhibitors
Inhibits integrase, the enzyme that helps to insert the viral cDNA strand produced by reverse transcriptase into the human genome
- prevents integration of proviral gene into human DNA
Name the Integrase Inhibitor drugs
raltegravir (Isentress)
dolutegravir (Tivicay)
What is complera
A NEW combination drug used for initial treatment of HIV-infected individuals
Complera contains what 3 medications
emtricitabine
rilpivirine
tenofovir disoproxil fumarate