Antivirals 1 and 2 Flashcards
Five major classes of antiretroviral meds:
- nucleoside reverse transcriptase inhibitors (NRTI’s); subset is nucleotide RTI’s (tenofovir)
- Non-nucleoside reverse transcriptase inhibitors (NNRTI’s)
- Protease inhibitors (PI’s)
- Entry inhibitors: enfuvirtide and CCR5 antagonists
- Integrase inhibitors
List NRTI’s:
Lamivudine, abacavir, tenofovir, emtricitabine;
TEAL
Mech of action of NRTI’s and analog posers:
viral DNA chain termination via inhibition of reverse transcriptase enzyme;
thymidine: zidovudine and stavudine (STarZ)
adenosine: didanosine, tenofovir (TAD)
Cytosine: zalcitabine, lamivudine, emtricitabine (CELZer)
Guanine: abacavir
List NRTI SE’s and the class SE’s:
- Tenofovir: nephrotoxicity (Fanconi, RTA)
- Abacavir: hypersens reaction (immune-mediated: if stopped do NOT restart; maybe HLA allele associated)
- Lamivudine/emtricitabine: few
- Zidovudine: anemia;
Lactic acidosis (much less common with new agents), and GI SE’s (N/V, diarrhea)
List of NNRTI’s, mech of action, and SE’s:
Efavirenz, nevirapine, rilpivirine, etravirine;
bind directly to reverse transcriptase and inhibits its action;
efavirenz: CNS symptoms like vivid dreams and drowsiness, and TERATOGENIC
Nevirapine: rash; hepatitis and hepatic necrosis
Etravirine: rash, increased LFT’s
Rilpivirine: rash, QT prolongation
Protease inhibitors and mech of action and class toxicities:
Ritonavir, fosamprenavir, lopinavir/ritonavir, atazanavir, darunavir;
Mech: bind within active pocket of protease, inhibiting binding of virus; without protease clevage, virus cannot cause infection (more flexibility regarding resistance);
Class toxicities: GI intolerances like N/V, diarrhea, with metabolic toxicities: dyslipidemia, hyperglycemia, lipodystrophy
What’s good about ritonavir:
Ritonavir at low doses ENHANCES blood levels of other PI’s when given together;
Inhibits P4503A4 inhibition in liver and gut, and inhibition of P-glycoprotein transport;
1. reduce dosing freq
2. improve adherence/reduce ADR’s
3. suppress strains of resistant virus
4. improve efficacy of regimen
Fusion inhibitors:
Enfuvirtide (salvage drug that can help after resistance develops); injection;
SE’s: local injection sight reaction, increased rate of bacterial pneumonia, hypersens rxn;
Maraviroc (CCR5 inhibitors)
SE’s: hepatotoxicity (rare); cough, fever, URI’s, rash, musculoskeletal symptoms, abdo pain, dizziness
Integrase inhibitors:
Raltegravir, elvitegravir, dolutegravir;
Mech: inhibits viral enzyme (integrase), which is necessary for insertion of viral DNA into human genomic DNA;
SE’s: Usually few adverse effects; nausea, headache, diarrhea, pyrexia; some MYOPATHY and RHABDO
Strength of recommendation for ART depends on; basics of HAART involves; examples for HAART
pre-treatment CD4 count;
combo therapy with at least 3 active agents (try to get 3 agents representative of 2 classes of agents);
- PI (maybe with ritonavir boosting) and 2 NRTIs
- NNRTI + 2 NRTIs
- Integrase inhibitor + 2 NRTIs
Goals of HAART:
- Undetectable viral load (within 24-48 wks of therapy, and if goal not reached, maybe change)
- CD4 response: should see rise in this count, but this will lag behind VL response
- Improve quality of life
- Reduce HIV-related morbidity and mortality
- Minimize resistance (if you develop it to antiretroviral it’s permanent, and cross-resistance can occur within classes; it’s directly associated with adherence and attainment of virologic goals)
When can we stop HIV treatment?
WE DON’T!!
HCV basics:
- No effective vaccine available
- Curable with effective drug therapy
- About 20% of individuals exposed to HCV will clear infection and not develop chronic HCV
From acute HCV infection, can progress to
chronic HCV infection, compensated cirrhosis, decompensated cirrhosis, and HCC, transplantation and death
For HCV, what is equivalent to a viral cure?
Sustained viral response (get undetectable HCV RNA 12-24 wks after therapy completion)
Interferon:
Mech: induce IFN-stimulated genes that help establish an antiviral state within cells (think pegylated form, and response not virus-specific);
SE’s: flu-like symptoms, cytopenias, depression, fatigue (FFCD); tough to finish treatment course; think contraindications
Ribavarin:
Nucleoside analog
SE: hemolytic anemia (major), teratogenic
Sofosbuvir:
Mech: inhibitor of HCV NS5B RNA-dependent RNA polymerase; once phosphorylated, competes with naturla viral nucleotide (uridine) to cause chain termination of HCV RNA (active across ALL HCV genotypes);
Toxicity: think fatigue, headache, GI SE’s, anemia
Ledipasvir
Mech: inhibits HCV NS5A, a viral phosphoprotein required for viral replication; combined with sofosbuvir;
SE’s: fatigue, headache, GI SE’s
Simeprevir, boceprevir, telaprevir
Mech: prevent viral maturation through inhibition of protein synthesis;
SE’s: anemia, rash, itching, GI SE’s, drug interactions (GRAID)
Approach to HCV therapy:
combo therapy is standard;
e.g. sofosbuvir and pegylated IFN and ribavarin for 12 wks
sofosbuvir and simeprevir w/w/o ribavirin for 12 wks
Acyclovir: what are some associated therapies also?
Mech: after phosphorylation by cellular enzymes, acyclovir triphosphate competes with DNA analogues to cause viral DNA chain termination
Thera: think HSV and VZV
SE’s: CNS (malaise, headache, confusion), N/V, diarrhea, renal dysfunction (high doses)
Misc: IV, oral, and topical formulations;
valacyclovir (prodrug of acyclovir converted to acyclovir after oral admin),
penciclovir has structure and MOA similar to acyclovir and given topically often;
famciclovir: prodrug of penciclovir that is given ORALLY!!
Ganciclovir:
Thera: HSV, VZV, and DEF CMV!!
Misc: IV/PO (valganciclovir is the prodrug with better bioavailability with food)
SE’s: myelosuppression (neutropenia), CNS toxicity (headaches, seizures, confusion), hepatoxicity and GI intolerance
Foscarnet
Mech: directly inhibits herpesvirus DNA polymerase or HIV reverse transcriptase; active against acyclovir/penciclovir/ganciclovir resistant viruses
Thera: inhibitory effect on herpesviruses and HIV
SE’s: nephrotoxicity, hypo/hypercalcemia, hypo/hyperphosphatemia, hypomagnesemia, hypokalemia; CNS SE’s (Hallucinosis, Irritability, SEIZURES, Tremors: HISTory), myelosuppression
