Q and A


How do I time my meds when travelling?

I am currently on Atripla (since Feb 08) and remain undectable.

Next week I am taking a vacation and we are going from the UK to the US. There is a 6hr time difference with the US being behind 6hrs. I usually take my Atripla around 11pm at night. I am really frightened and concerned and dont know what to do?

If I don’t adjust the times then i will be taking my meds at 5pm US time which will mean I could be wiped out from the side effects for the rest of the evening? However, I dont want to risk taking them at 11pm US time, as it will mean that I am 6hrs late taking my Atripla, which could lead to resistance. What should i do?

Thanking you in advance and i would really appreciate if someone was able to give me advice as we travel in a few days.


Thanks for your question.

For someone who is using Atripla (efavirenz+tenofovir+FTC) and has had an undetectable viral load for many months (or years) it is probably easiest to just switch to US time on your first night.

Although this risks low drug levels for up to 6 hours, this is just like forgetting one days meds, which even someone with the best adherence is likely to do at least once or twice. Although this isn’t the best scientific answer, in practice, missing one dose for a few hours is unlikely to do any harm – see this previous question on this.

This approach is also supported by a study called FOTO (Five On Two Off) where people with undetectable viral load on Atripla, were randomised to either continue on 7-day dosing or change to taking meds for 5 days a week and not for 2 days at weekends. After one year, the people on the 5-day strategy all still had undetectable viral load.

While I think that the FOTO study is too small a study to support people switching routinely to the 5 days on/2 days off strategy, I think it provides interesting evidence to support the general safety from extending, or missing, one dose of Atripla.

Scientifically, and for people using other combinations, the main options when travelling to different time zones is either to stay on UK times (ie taking them at different local times – 5pm rather than 11pm UK time n your example) or to switch to the same time of day in the new time zone. For anything other than a very short trip, it is usually easier to change to the new time zone – ie so if you take meds at 11pm in the UK to take them at 11pm on your holiday time zone.

When changing the schedule the main principal is that it is easier and safer to bring forward your dose time then is is to extend it. For a twice-daily drug you don’t want to leave it longer than 12 hours, but it is fine to bring one dose forward, even by 6 hours, if that gets you on the same local time at your destination. With a once-daily drug, you don’t want to go past 24 hours, but could bring it forward by 6, 8 or even 12 hours.

Although bringing froward a dose will give you slightly higher levels of each drug, this is very safe for such a short period.

When returning to the UK, bringing the dose forward to get you on UK time with your first dose is fine for the same reasons.

Reference: 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. 5th IAS Conference, 2009. Abstract MOPEB063.


  1. Josh Peasegood

    Hi Morgan, if it still fits with your schedule, being an hour out is not going to impact how the ARVs work. You can either keep with Nigerian time and take them at 8pm or there would be no issue if you moved this to 9pm in the UK.

  2. Morgan

    Hi,I normally take my ARV by 9pm when I was in Nigeria,now that I’m in uk which is an hour behind Nigerian time,what time should I take the medication now that I’m in uk?

  3. Lisa Thorley

    Hi Chet,

    No you don’t need to change the time that you take your meds, just take them at your normal time.

  4. Chet

    Hi, if I’m traveling from China to Japan, which is one hour ahead, do I need to change my meds schedule? I usually take mine (dtg/ftc/taf) at 9pm, which is 10pm in Japan. Does it make any difference whether I take it at 9pm or 10pm Japan time? Thanks!


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