Importantly, triple regimen persistence should be investigated in order to provide information on the permissiveness (of forgotten or delayed doses) of the whole regimen rather than one single agent. Due to the simplicity of administering Atripla®, a study investigating the pharmacokinetic "forgiveness" of tenofovir and emtricitabine (in plasma and intracellularly) and plasma efavirenz would be readily performed in healthy volunteers and would provide information on how to advise HIV infected patients on delayed and missed doses.