They are both right. The prescribing information for Epclusa recommends that people not take Prilosec (omeprazole) or other proton-pump inhibitors (PPIs) unless medically necessary. If it is unavoidable, then Epclusa should be taken with food, followed by the PPI four hours later. Do not exceed the maximum dose of the PPI.
For people taking Harvoni, the recommendations are different. Harvoni and the PPI should be taken together under fasting conditions, such as first thing in the morning.
If your doctor prescribes a different type of acid-reducing medication, be sure to ask when and how to take the new medication. Generally, H2 blockers such as Zantac or Pepcid may be taken with Epclusa or Harvoni, or they should be taken 12 hours apart. Antacids such as Tums need to be separated by four hours before or after taking Epclusa or Harvoni.