Are over-the-counter flea treatments as effective as prescription ones?

Across the reviewers we read, the consensus is that OTC topicals like K9 Advantix II, Frontline Plus and Advantage II still work well in most regions, but specialist subreddits (r/cats, r/Pets, r/dogs) increasingly flag regional flea resistance — particularly to Frontline — and recommend vet-prescribed options like Revolution Plus or Bravecto when an OTC product fails after one or two cycles.