Atazanavir with Cobicistat

How it works

Atazanavir inhibits HIV protease, preventing cleavage of viral polyproteins into mature infectious virions, while cobicistat has no antiviral activity but inhibits CYP3A to boost and sustain atazanavir plasma concentrations.

Prescribing in practice

• Cobicistat is a potent CYP3A inhibitor that causes numerous clinically important drug interactions, so a full interaction check is essential before co-prescribing and certain medicines are contraindicated.
• Acid-reducing agents markedly reduce atazanavir absorption, so proton pump inhibitors and other antacids require careful timing or avoidance, and the combination should be taken with food.
• Unconjugated hyperbilirubinaemia causing visible jaundice is common and benign but can be distressing, and atazanavir may also cause nephrolithiasis and cholelithiasis.

Monitoring

Monitor viral load, CD4 count, bilirubin, renal and hepatic function, and review concomitant medicines for interactions.

Counselling the patient

• Take the tablets with food and keep a regular daily routine.
• Yellowing of the eyes or skin can occur and is usually harmless, but report it so it can be assessed.
• Check with the team before taking any antacid, indigestion remedy or new medicine.

Evidence & guidelines

Boosted atazanavir is an established protease-inhibitor option in UK HIV guidelines, with cobicistat providing pharmacokinetic enhancement comparable to ritonavir.