Q and A


Should I worry about an Atripla dose that is 4 hours late?

I was diagnosed with HIV just barely over a year ago. Because my CD4 count was low my doctor prescribed Atripla.

Within 3-4 months of being on the drug my CD4 count had jumped up to over 800 (from 370) and my viral load dropped to undetectable. I’ve been taking it really carefully and on-time or within an hour and my last labs showed that my CD4 count was reconstituted and my VL was still undetectable.

Last night I had my first blunder. I went out to a birthday party with at a friends house and I forgot my pill at home. It was about 4 hours late. Could this mishap unravel all work I had done to keep my CD4 up?



From the circumstances you describe there is no need to worry. Being late with one dose will not have affect your health in any way.

It is only if you regularly miss doses or are late with Atripla that the chance of developing resistance becomes a real concern.

The three drugs in Atripla (efavirenz, FTC and tenofovir) all have good concentrations at the end of each 24-hour dose to cover you for a few hours either way.

One study included this combination in an unusual combination. The study was called FOTO for Five days On Two days Off, and it followed people taking Atripla on weekdays and missing the two days at the weekends. After one year everyone still had a viral load that was undetectable (less than 50 copies/mL).

No treatment guidelines recommend following the FOTO strategy, but it is a good example of how an occasional missed dose of Atripla is unlikely to do any harm.

FOTO STUDY: Cohen C et al. The FOTO study: The 48 week extension to assess durability of the strategy of taking efavirenz, tenofovir and emtricitabine Five days On, Two days Off (FOTO) each week in virologically suppressed patients. IAS 2009, Cape Town. Abstract MOPEB063.


  1. Roy Trevelion

    Hi Joseph,

    What ARVs are your taking? And has this happened lots of times?

    Simon has answered this question about Atripla, you can read it above.

    What are the reasons for being late? Here are some tips about taking your ARVs at the right time.


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