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# Atazanavir
## Overview
Atazanavir is a protease inhibitor used in the treatment of HIV infection. It is typically used in combination with other antiretroviral agents.
## Primary Indications
* Treatment of HIV-1 infection in adults and pediatric patients (6 years and older or weighing at least 15 kg) in combination with other antiretroviral agents.
## Adult Dosing
* **Standard Dose:** 300 mg once daily, administered orally with ritonavir 100 mg once daily, and with food.
* **Alternative (without ritonavir, for specific regimens):** 400 mg once daily, administered orally with food. This dosing is less common due to higher rates of hyperbilirubinemia and virologic failure compared to the ritonavir-boosted regimen.
## Pediatric Dosing
* **Patients 6 years to 18 years of age (and weighing ≥15 kg):**
* **With ritonavir:** 100 mg/m² or 6 mg/kg once daily, capped at 300 mg, administered orally with ritonavir 100 mg once daily and food.
* **Without ritonavir:** 150 mg/m² or 12 mg/kg once daily, capped at 400 mg, administered orally with food.
* **Weight-based dosing for pediatric patients weighing less than 15 kg is not established.**
## Dose Adjustments
* **Hepatic Impairment:**
* **Mild to moderate:** No dose adjustment is recommended.
* **Severe:** Use with caution; dosage recommendations are not established.
* **Renal Impairment:** No dose adjustment is necessary in patients with mild to moderate renal impairment. Data are limited in severe renal impairment or end-stage renal disease; use with caution.
## Contraindications
* Concurrent use with rifampin, phenobarbital, carbamazepine, phenytoin, St. John's wort, and ergot derivatives.
* Known hypersensitivity to atazanavir or any of its components.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, headache, rash, abdominal pain, jaundice, indirect hyperbilirubinemia (prolonged unconjugated hyperbilirubinemia).
* **Serious:** Hepatotoxicity, severe skin reactions (including Stevens-Johnson syndrome), QT interval prolongation, rhabdomyolysis, nephrolithiasis, cholelithiasis, lipodystrophy, immune reconstitution inflammatory syndrome (IRIS).
## Key Drug Interactions
* **CYP3A4 Inducers:** Reduce atazanavir concentrations (e.g., rifampin, phenytoin, carbamazepine, phenobarbital, St. John's wort).
* **CYP3A4 Inhibitors:** May increase atazanavir concentrations (use with caution, potential for increased adverse effects).
* **P-gp Substrates:** Atazanavir may increase concentrations of P-gp substrates (e.g., digoxin, some chemotherapy agents).
* **Antacids and H2 Receptor Antagonists/Proton Pump Inhibitors:** May decrease atazanavir absorption; separate administration by at least 2 hours.
* **Didanosine:** Coadministration with buffered didanosine is not recommended. If coadministration is necessary, separate doses by at least 2 hours, and give atazanavir with ritonavir and food.
* **Statins:** Increased risk of myopathy and rhabdomyolysis. Avoid simvastatin and lovastatin; use with caution with atorvastatin and rosuvastatin, potentially with dose reduction.
* **Ergot Derivatives:** Atazanavir is contraindicated with ergot derivatives due to risk of ergotism.
* **Boceprevir, Telaprevir:** Interactions are complex and dose adjustments are required; consult specific guidelines.
## Monitoring
* **Baseline:** HIV viral load, CD4+ T-cell count, liver function tests (LFTs), renal function, serum amylase, bilirubin.
* **During Therapy:** Monitor HIV viral load and CD4+ T-cell count (for efficacy), LFTs (especially with co-administered hepatotoxic drugs), bilirubin (for hyperbilirubinemia), renal function, lipids, glucose, and for signs of lipodystrophy, rash, or other adverse effects.
## Clinical Pearls
* Atazanavir should be administered with ritonavir (boosting) to increase plasma concentrations, improve efficacy, and reduce the risk of hyperbilirubinemia and virologic failure, especially in treatment-naive patients.
* Administer atazanavir (with or without ritonavir) with food to enhance absorption.
* The most common reason for discontinuing atazanavir is rash.
* Jaundice and indirect hyperbilirubinemia are common and usually manageable by dose reduction or interruption, but significant elevations warrant further evaluation.
* Atazanavir is associated with a higher risk of cardiovascular events compared to some other protease inhibitors; consider patient risk factors.
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*This information is intended for healthcare professionals and should not be a substitute for professional medical advice. Always consult the most current prescribing information and relevant clinical guidelines before making any treatment decisions.*
