Darunavir with cobicistat, emtricitabine and tenofovir alafenamide

How it works

Darunavir inhibits HIV protease to prevent maturation of viral particles while cobicistat boosts its levels by inhibiting CYP3A; emtricitabine and tenofovir alafenamide are incorporated into viral DNA by reverse transcriptase, causing chain termination.

Prescribing in practice

• Cobicistat is a potent CYP3A inhibitor that causes numerous serious drug interactions, so screen all co-medications (including statins, ergot derivatives, certain sedatives, antiarrhythmics and the contraceptive pill) before and during therapy.
• Darunavir is a sulfonamide derivative, so use with caution in patients with a known sulfonamide allergy and monitor for rash.
• Cobicistat inhibits tubular creatinine secretion, producing a small early rise in serum creatinine without a true fall in glomerular filtration, which should not be mistaken for renal impairment.

Monitoring

Monitor HIV viral load and CD4 count to confirm virological response, alongside renal function, liver function and lipids during treatment.

Counselling the patient

• Take the tablet once daily with food to optimise absorption.
• Do not start any new medicine, including herbal remedies such as St John's wort, without checking for interactions.
• Continue taking every day to keep the virus suppressed and reduce the risk of resistance.

Evidence & guidelines

Use of antiretroviral therapy in HIV is guided by BHIVA and NICE recommendations, with treatment selected and monitored by specialist HIV services.