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Prezcobix is a two-drug combination regimen fusing darunavir (brand name Prezista) with cobicistat (Tybost). Darunavir belongs to a class of drugs called protease inhibitors. Protease inhibitors (or PIs) use to be the HIV drugs with the highest pill burden and the most side effects — but not any longer. PIs stop HIV from multiplying.
Cobicistat, meanwhile, is a booster drug that increases the effectiveness of HIV medicines. In a clinical study, 70 percent of adults maintained an undetectable viral load (rendering them un-infectious) with a darunavir-based HIV regimen. Prezcobix is useful for adults with HIV new to treatment and those who haven’t developed resistance to darunavir.
Prezcobix must be combined with at least two other HIV treatments (usually nucleoside analogues, or ‘nukes’, which help prevent the CD4 cells from producing new HIV). Dosing is one tablet once a day to be taken with food, with each pink pill consisting of 800mg of darunavir and 150mg of cobicistat.
Although generally well-tolerated, common side effects of Prezcobix include diarrhoea, nausea, vomiting, headache and abdominal pain. Skin rash is another common side effect, although Prezcobix manufacturers, Janssen, report the rash to be “mostly mild-to-moderate”, and often only occurring within the first four weeks of commencing treatment before resolving over time. (If, however, the rash is severe it’s recommended that you contact your healthcare provider immediately.)
As well, Prezcobix may cause liver problems. As a result, liver function tests will be carried out before and during treatment. People with HIV co-infected with hepatitis B and hepatitis C have an increased chance of developing liver problems so liver function will be monitored more regularly. Kidney injury can also sometimes occur or grow worse when Prezcobix is taken with other medicines. There is also a risk of diabetes or worsening diabetes, and high-blood sugar. Increased levels of insulin have also been noted, as have changes in body fat (fat wasting and fat gain).
As a booster agent, the cobicistat component increases the levels of other drugs in the body, which may increase the risk of serious side effects — always be sure to inform your healthcare provider of any other medications you may be taking (including prescription and over-the-counter medicines, vitamin supplements and herbal remedies).
Prezcobix should not be used during pregnancy as its safety on that population has not been studied. Janssen also advises that caution should be taken “in the administration and monitoring of Prezcobix in elderly patients”.
In short: Prezcobix lowers pill burden, which eases adherence, and has less toxicity and higher tolerability than older PIs.