Atazanavir Cannot Be Combined with Antacids Due to Decreased Absorption
Atazanavir is the antiretroviral drug that cannot be combined with antacids because its absorption is significantly reduced in higher gastric pH environments, potentially leading to treatment failure and development of resistance. 1, 2
Mechanism of Interaction
- Atazanavir requires an acidic gastric environment for proper dissolution and absorption 2
- Antacids increase gastric pH, which significantly reduces atazanavir's solubility and bioavailability 1
- This interaction results in decreased minimum concentration, area under the curve, and maximum concentration of atazanavir 2
- The reduced drug levels can lead to subtherapeutic concentrations, increasing the risk of virologic failure and development of HIV drug resistance 2
Clinical Management Options
- If antacid therapy is absolutely necessary in patients taking atazanavir: 2
- Use atazanavir boosted with ritonavir (300mg atazanavir/100mg ritonavir) to partially mitigate the interaction
- Consider therapeutic drug monitoring of atazanavir levels
- Separate administration times (give antacids at least 2 hours before or 6 hours after atazanavir) 3
- Consider alternative antiretroviral options that don't interact with antacids: 4
- Lopinavir/ritonavir has been shown not to have significant interactions with acid-reducing agents
Other Antiretrovirals and Acid-Reducing Agents
- Ledipasvir (used in HCV/HIV coinfection) also has decreased solubility as pH increases, requiring careful management with acid-reducing agents 5
- Indinavir is another protease inhibitor requiring acidic environment for absorption 2
- Daclatasvir, sofosbuvir, and raltegravir do not have clinically significant interactions with antacids 5
Important Caveats
- The interaction between atazanavir and acid-reducing agents extends beyond antacids to include: 1, 2
- Proton pump inhibitors (omeprazole, esomeprazole, etc.)
- H2-receptor antagonists (ranitidine, famotidine, etc.)
- Even with ritonavir boosting, concurrent use of atazanavir with proton pump inhibitors may still result in suboptimal drug levels 2
- Didanosine formulations contain buffers that can act as antacids, requiring separation of dosing with atazanavir 3
Monitoring Recommendations
- If a patient on atazanavir requires acid-reducing therapy: 2
- Monitor HIV viral load more frequently to ensure continued virologic suppression
- Watch for signs of treatment failure (increasing viral load)
- Consider checking atazanavir drug levels if available
- Be vigilant for development of resistance mutations