Treatment of HIV and Opportunistic Infections Flashcards
Why can full eradication of HIV not be achieved through antiretrovirals?
A pool of latently infected CD4 cells is established during early stages of HIV infection
Why might it be difficult to achieve viral suppression in some cases?
Due to pre-existing mutations, even in patients which haven’t seen therapy before
What are the 6 different classes of HIV drugs? Which are never relied on unless last line?
- Nukes - Nucleoside Reverse Transcriptase Inhibitors
- Nonnukes - Non-nucleoside RT inhibitors
- Protease Inhibitors
- Integrase inhibitors
- CCR5 antagonists
- Fusion inhibitors
5/6 never relied upon unless resistance
What do first line treatment regimens consist of?
Two NRTIs + a backbone
What is a backbone?
An integrase inhibitor (first line) or Boosted PI or One NNRTI (no longer first line due to CNS effects)
What are the two most common 2-NRTI backbones?
- Abacavir / lamivudine
2. Tenofovir / emtricitabine
Why are integrase inhibitors really good?
Low pill burden
Well tolerated
Fewer drug interactions
Newest agent + high barrier to resistance
What was the first integrase inhibitor available and what are its side effects?
Raltegravir
Well-tolerated minus GI side effects
Potential CPK elevations / rhabdomyolysis (similar to daptomycin)
What are the two drug interactions we worry about with raltegravir?
Substrate of secondary metabolism enzymes (not a CYP inhibitor):
Dose must be doubled with rifampin
Binds divalent cations
What is Elvitegravir and what does it need to be given with?
An integrase inhibitor, needs to be given with cobicistat, a CYP3A4 inhibitor, for boosting
What side effects do we worry about with elvitegravir / cobicistat?
Cobicistat inhibits creatinine secretion like TMP
Tenofovir is given with elvitegravir and is nephrotoxic - patient needs a creatinine clearance of >30 (nitrofurantoin was >60)
What is one drug interaction of ALL integrase inhibitors?
Binds divalent cations - similar to FQ and tetracyclines
Which integrase inhibitor is super lit and why?
Dolutegravir - has a long-halflife so you can do once-daily dosing
Also has higher genetic barrier to resistance than other integrase inhibitors
In what way is dolutegravir similar to colbicistat?
Slightly blocks tubular secretion of creatinine
What drug-drug interactions do we worry about with dolutegravir?
Other than divalent cations:
It doubles metformin concentrations, and it is CYP-metabolized so dose needs to be doubled with Rifampin
What is the mechanism of action of protease inhibitors?
Bind HIV protease, which are needed to activate the HIV polyproteins
What is Ritonavir and its use?
It is a PI, but mainly used in HIV regimens as a POTENT CYP3A4 inhibitor, as a booster. All PIs interact with CYP3A4 to some degree
Being used less with colbicistat on the market now
What is the preferred PI based regimen?
Darunavir + ritonavir
What are the side effects of PI based regimens?
Dyslipidemia, fat maldistribution, insulin resistance, GI side effects including diarrhea, and skin rash
What are the advantages and disadvantages of PI based regimens?
Advantages: High genetic barrier to resistance
Disadvantages: Metabolic complications, GI side effects, and CYP3A4 issues
What is the preferred NNRTI? When is it not preferred?
Efavirenz
Not preferred during pregnancy because it will “Ef” your baby up with neural tube defects
What is the preferred alternative to Efavirenz during pregnancy?
Nevirapine - it’s “nevir” gonna fuq up your baby
What is the mechanism of action of NNRTI’s and what about them is both good / bad?
Suicide inhibitor of RT.
Their long halflife is good and bad: fewer pills are needed, but if compliance is not at least 95% there will be subtherapeutic concentrations and resultant low barrier to resistance
What are the scary adverse effects of Efavirenz other than NTDs?
- CNS / psychiatric symptoms leading to a 2-fold increase in suicide
- Rash / Steven-Johnsons Syndrome is possible
What are the side effects of concern with Nevirapine?
Skin rash and hepatotoxicity
What is the mechanism of action of NTRIs?
Like acyclovir, they implant into the RT chain and act as chain terminators
What are the two class adverse events to remember for NRTI’s?
- Lactic acidosis
2. Hepatic steatosis / lipoatrophy
What is the reaction to test for in Abacavir (part of the standard Abacavir / lamivudine regimen)?
Abacavir hypersensitivity reactions, with fever, rash, fatigue, and abdominal pain
Associated with one particular HLA allele - test for this!
What is the safest and most well tolerated NRTI?
Lamivudine
What are the side effects of concern with tenofovir and how has this been mitigated?
Renal toxicity / Fanconi syndrome - avoided in renal insufficiency
Now made as a prodrug which converts to active form in target cells, keeping serum concentrations lower
Why is zidovudine now rarely used?
It was the original NRTI (AZT)
No longer used due to bone marrow toxicity
What is currently the only drug in the fusion inhibitor class, and what is its mechanism of action?
Enfuvirtide
Binds to gp41, needed for entry of virus into cell
What is the the major side effect of concern for enfuvirtide?
Injection site reactions, since it must be given twice daily subcutaneously
What is Maraviroc? When is it useful?
A CCR5 antagonist -> given to treatment experienced patients whose HIV is still M-tropic
What is the metabolism of Maraviroc?
CYP3A4
What are the three side effects of concern for Maraviroc?
- Rash / pruritis (From immune dysfunction)
- Hepatotoxicity
- Arthralgia / myalgia
At which CD4 count do we worry about PCP and what is the prophylaxis?
CD4 <200
Prophylaxis: TMP / SMX, or dapsone (similar to sulfa, PABA antagonist), also pentamidine
What is secondary prophylaxis as it relates to PCP pneumonia?
If patient has had PCP, they will get TMP/SMX prophylaxis for life
What is the PCP treatment of choice?
High dose TMP/SMX for 21 days, with option of corticosteroids to reduce inflammation in moderate/severe
What is pentamidine and when is it used?
Can be used in PCP for prophylaxis or leishmania
Interferes with protozoal RNA / DNA/protein synthesis
What are the adverse drug effects and interactions of pentamidine?
ADE: Bone marrow suppression, hepatoxicity, nephrotoxicity
Interactions: CYP2C19 substrate - interacts with AZOLE antifungals
When should Mycobacterium avium complex prophylaxis start? What is it? When should it be stopped?
When CD4 < 50, it is Azithromycin or Clarithromycin once weekly
Stopped when CD4 > 100 for 3 months
What is the MAC treatment?
Two or more anti-mycobacterial drugs to prevent resistance.
First line: Clarithromycin + Ethambutol + sometimes rifabutin
What is rifabutin?
A derivative of rifampin, still induces CYP3A4 though
What patients are at greatest risk of Cryptosporidiosis? What is the presentation?
When CD4 <100
Present with acute onset of non-bloody watery diarrhea and abdominal symptoms
What is the prophylaxis and treatment for Cryptosporidiosis??
Prophylaxis - none, just get CD4 count back up
Treatment: symptomatically rehydrate. Possible Nitazoxanide (Knit-Sox)
When is T. gondii prophylaxis recommended, and what is the most common presentation? What is the prophylaxis?
CD4 < 100
Prophylaxis: TMP / SMX or dapsone
What is the treatment for T. gondii encephalitis and why?
Pyrimethamine (pyramid hat) + sulfadiazine (sulfur eggs next to cat)
Penetrates BBB well and you need to treat CNS infection
What is the mechanism of action of pyrimethamine?
Inhibits parasitic dihydrofolate reductase (similar to TMP, synergistic with sulfadiazine, a sulfa derivative)
What is co-administered with pyrimethamine / sulfadiazine and why?
Pyrimethamine causes bone marrow suppression.
Leucovorin is a reduced form of folic acid, allows purine synthesis in our cells but not the parasite
What is the metabolism of pyrimethamine? Pentamidine?
Pyrimethamine: CYP3A4
Pentamidine: CYP2C19
At what CD4 count are we worried about CMV and what is its most common presentation?
CD4 < 100, same concern as Toxo and Crypto
Concern for retinitis, but can also caused colitis, pneumonitis, and neurological disease
What is the primary treatment for CMV + side effect?
Ganciclovir / valganciclovir. Worry about bone marrow suppression
How do you remember the two protease inhibitors given together?
In the sketchy sketch: ritonavir = right on! kids high-fiving
Darunavir - looks like old times, kid pulling the sword from the stone. Runescape! Da Runa -vir!
