Prezista (darunavir) is an antiretroviral medicine used as part of combination treatment for HIV-1 infection. It belongs to the protease inhibitor class and works by blocking the HIV protease enzyme, which the virus needs to produce new, mature, and infectious particles.

Darunavir is a second-generation protease inhibitor that retains activity against many HIV strains resistant to earlier protease inhibitors. It must always be given with a pharmacokinetic booster: either ritonavir (Norvir) or cobicistat (as in the combined tablet Prezcobix).

Prezista must always be taken with a booster: either ritonavir 100 mg or cobicistat 150 mg.

Take with food at the same time each day. Swallow tablets whole.

The correct Prezista dose depends on your treatment history and resistance profile. Your HIV doctor will determine the right dose and schedule for your individual situation.

Take the missed dose with food as soon as you remember. If it is nearly time for the next dose, skip and continue your schedule. Never take a double dose.

Contact your HIV specialist or a poison control centre.

• Store below 30°C
• Keep in the original container
• Keep out of reach of children

Common side effects:

• Diarrhoea
• Nausea
• Headache
• Rash: includes the risk of serious skin reactions in rare cases
  
  

Less common but important:

• Liver enzyme elevations
• Raised cholesterol and triglycerides
• Raised blood sugar levels
• Fat redistribution (lipodystrophy): body fat may accumulate in unusual areas

Regular monitoring of blood lipids, liver function, kidney function, and viral load is required.

Prezista is always taken with ritonavir (or cobicistat), which acts as a booster. This booster slows the breakdown of darunavir in your body so it stays at effective levels but it also affects how your liver processes many other medicines, which is why interactions are more common with Prezista than some other HIV treatments.

• Statins (cholesterol medicines): Simvastatin and lovastatin cannot be used with Prezista. The booster causes statin levels to build up significantly, raising the risk of serious muscle damage. Other statins may be used at adjusted doses. Let your doctor know if you take any cholesterol medicine.
• Rifampicin (antibiotic): Cannot be used together. Rifampicin dramatically lowers darunavir levels, making your HIV treatment ineffective.
• Anticonvulsants (carbamazepine, phenytoin, phenobarbital): These reduce darunavir levels in your blood. Your doctor will need to know if you take any of these for epilepsy or nerve pain.
• St John's Wort: This herbal supplement speeds up the breakdown of darunavir and should not be used while you are on Prezista.
• Hormonal contraceptives: Prezista can reduce the effectiveness of the pill, patch, or ring. Use an additional form of contraception and discuss options with your doctor.
• Warfarin: If you take warfarin as a blood thinner, your INR levels may shift. Your doctor will monitor this more closely when starting or changing your Prezista dose.
• Medicines for heart rhythm, anxiety, or sleep: Some medicines in these categories are affected by the booster. Always tell any prescriber or pharmacist that you are on Prezista before starting something new.

Why does darunavir need a booster?

Darunavir is broken down quickly by liver enzymes if taken alone. Without a booster, the dose required to maintain sufficient blood levels would be very large and impractical. Adding ritonavir or cobicistat at a low dose blocks the enzyme responsible, extending darunavir's time in the body and allowing a much lower dose to be effective. This approach, called pharmacokinetic boosting, is used with several HIV protease inhibitors.

Is Prezista effective against resistant HIV?

Yes. Darunavir is specifically designed to bind tightly to the HIV protease enzyme even when some resistance mutations are present. It requires accumulation of multiple specific mutations (at least three of a defined set) before resistance becomes clinically significant, giving it a higher genetic barrier to resistance than older protease inhibitors.

Ace provides accurate and independent information medically reviewed on prescription medications. This material is provided for educational purposes only and is not intended for medical advice, diagnosis or treatment.