Patients are randomized to either continue their current Videx tablet-containing regimen for an additional 2 weeks or replace their Videx tablets with Videx EC. Patients who remain on Videx tablets are switched to the EC formulation at Study Week 2 for the remaining 4 weeks of the study period. For patients who continue and successfully complete the Week 6 study visit, an optional extended dosing period is offered until Videx EC becomes commercially available or the study funder terminates the study. Blood specimens for safety evaluations and viral load are collected at Weeks 0, 1, 2, 4, and 6. For patients participating in the extended dosing period, the visit schedule is every 8 weeks. Symptom scores between the 2 treatment groups are compared, with the primary comparison occurring at the Week 2 visit. Analyses include changes in GSRS scores administered by clinician interview at each study visit. Assessment of GI symptoms, palatability features, dosing convenience, lifestyle effects, and Videx preference is evaluated by the patient. Adverse events are assessed objectively by the observations of both the investigator and the patient.