In my case, I had minor GERD problems for years and took omeprazol off an on, but suddenly had very serious
acid reflux.
Acid was actually eating away the enamel on my teeth and distroying my vocal cords, and until I could have a Nissen Fundoplication procedure, I was taking six omeprazol a day; two 1/2 hour prior to breakfast, lunch and dinner. It helped, and I had no negative symptoms whatsoever from the meds.
By the way, the Nissen Fundoplication was a complete success.