Knowledge of the pharmacokinetic forgiveness of a drug “allows a clinician to advise a patient on how long a dose may safely be delayed during travel,” the authors stated.1 For patients with known resistant virus in-flight dosing should be considered, however.1 Complex itineraries and traveling across multiple time zones can be a particular challenge and “may require more careful planning and may require in-flight dosing,” they cautioned.1

Reviewing the available research literature, the authors classified lopinavir/ritonavir (once-daily), unboosted atazanavir, and monotherapy with boosted atazanavir or lopinavir, to be “likely to be poorly tolerant of late dosing.”1 Travellers on these regimens should “take an extra dose in-flight” and take all subsequent doses according to the new time zone upon arrival, they advised.1

In contrast, tenofovir, emtricitabine, lamivudine, abacavir, and didanosine are “likely to be tolerant of late dosing,” they reported.1 For these regimens, once-daily dosing should be adjusted to take doses before travel and after arrival. (Efavirenz once-daily should not be taken immediately before departure. “Instead, dosing can be safely stretched from previous evening,” they advised.1) Twice-daily regimens listed as likely tolerant of late dosing, should be adjusted to dose-intake prior to departure if a flight is 12 hours long or less, or to take an extra dose in-flight at the patient’s convenience, if the flight is longer than 12 hours, and to take the next dose after arrival, the authors recommended.1

Nevirapine once- or twice-daily regimens are also likely to be tolerant of late dosing and should be dosed according to the new time zone upon arrival.1 The same is true for rilpivirine once-daily, boosted atazanavir once-daily, boosted darunavir once- or twice-daily, boosted elvitegravir once-daily, dolutegravir once- or twice-daily, and maraviroc once- or twice daily. 1 

The risk of travel is lowest “when the patient is stable on their cART with a well-suppressed viral load,” the authors emphasized.1

“While it is important to relate the pharmacokinetics of drugs and the effect of extended or shortened [dosing] intervals, it is difficult to use in practice for short-term time disruptions associated with travel,” comments travel pharmacist Jeffery Allen Goad, MPH, PharmD, a professor at Chapman University in Irvine, California, and a past chairman and founding member of the Pharmacists Professional Group Section of the International Society of Travel Medicine. Professor Goad was not involved in preparation of the newly-published review paper.