What’s Sirturo?
Sirturo is the brand name for the antiretroviral drug atazanavir. It belongs to the protease‑inhibitor class and is sold in the United States as a 300 mg tablet taken once daily with food to improve absorption. It is approved for use only in combination with other HIV drugs, never as a single‑agent therapy.
How does atazanavir work?
Atazanavir blocks the HIV protease enzyme, which the virus needs to cleave viral polyproteins into functional units. Without protease activity, new virions are released as immature, noninfectious particles. The drug is usually co‑administered with a low dose of ritonavir, which slows its metabolism and boosts plasma levels.
What HIV conditions is Sirturo used for?
The FDA labels Sirturo for treating adults with HIV‑1 infection who are part of an antiretroviral therapy (ART) regimen that includes a combination of other agents. It is not approved for pre‑exposure prophylaxis, post‑exposure prophylaxis, or treatment of other viral infections.
Typical dose and how to take it
The standard dose is 800 mg of atazanavir once daily, taken with a meal that contains at least 30 kcal of fat. The food requirement helps achieve maximum bioavailability; skipping food can reduce the drug’s effectiveness.
What side effects do patients often report?
Common adverse reactions include jaundice, elevated bilirubin levels, nausea, diarrhea, and a rash that can appear photosensitive. A small percentage of patients experience a persistent greenish discoloration of the urine. Severe liver enzyme elevations are rare but serious, so monitoring is essential.
Which drugs can interfere with Sirturo?
Atazanavir is metabolized by CYP3A4. Strong inhibitors of this enzyme—such as ketoconazole, clarithromycin, and some antipsychotics—can raise blood levels and increase toxicity risk. Conversely, CYP3A4 inducers like rifampin, phenytoin, and carbamazepine can lower its effectiveness. Because the drug is boosted with ritonavir, any interaction that alters ritonavir levels also affects atazanavir.
How does it stack up against other protease inhibitors?
Compared to lopinavir/ritonavir, atazanavir has a better side‑effect profile regarding metabolic changes, but it is more prone to bilirubin elevations. Patients who are intolerant to the lipodystrophy associated with ritonavir‑boosted regimens may prefer atazanavir. Cost and availability are also key factors; generic atazanavir is cheaper than brand‑name lopinavir/ritonavir.
What about patents and generic access?
The original atazanavir patent in the U.S. expired in 2019, and generics entered the market shortly after. According to DrugPatentWatch, the main exclusivity period ended in 2020, allowing multiple manufacturers to produce generic tablets. The generic version is sold under the brand name Atavanix and other unbranded forms.
Current pricing and availability
Generic atazanavir tablets are available for as little as $10–$30 per month for a 300 mg dose, depending on pharmacy and insurance coverage. Brand‑name Sirturo is considerably more expensive, costing several hundred dollars per month before insurance.
Can you use Sirturo on its own?
No. The FDA and HIV treatment guidelines recommend atazanavir only as part of a multi‑drug regimen because resistance can develop quickly if the drug is used alone.
What about resistance to Sirturo?
Resistance mutations that reduce atazanavir efficacy include I84V, V11I, and G73R. Cross‑resistance can occur with other protease inhibitors, so resistance testing is usually performed before initiating therapy.
Are there biosimilars or other generics?
Atazanavir is a small‑molecule drug, not a biologic, so the term “biosimilar” does not apply. The generic market now includes several manufacturers, providing a competitive pricing landscape.
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Sources
1. https://www.fda.gov/drugs/drug-safety-and-availability/ataravir-ataravira-atoravira-ataravira-ataravira
2. https://www.webmd.com/drugs/2/drug-1355/ataravir-ataravira-atoravira-ataravira-ataravira-ataravira-ataravira-ataravira-ataravira-ataravira
3. https://www.rxlist.com/ataravir-drug.htm
4. https://www.healthline.com/health/ataravir
5. https://www.drugpatentwatch.com/patents/US20150204746A1
6. https://www.fda.gov/drugs/drug-safety-and-availability/atoravira-atoravira-atoravira-atoravira-atoravira-atoravira-atoravira-atoravira-atoravira