Aspirin and many other nonsteroidal anti-inflammatory drugs (NSAIDs), (eg, ibuprofen, naproxen, indomethacin, and ketorolac) are carboxylic acids. Their pKa values range from 3.50 (aspirin) to 4.85 (ibuprofen). As such, they are not ionized at the acidic pH found in the gastric lumen and thus can be absorbed across the gastric mucosa. Once these drugs move from the acidic environment of the gastric lumen into the pH–neutral mucosa, the drugs ionize and are trapped temporarily in epithelial cells where it may damage these cells. How important is this effect? Calcium carbsalasate does not have this epithelium damaging topical effect, but causes the same ulcerative outcome[1].

This "topical" epithelial injury by many NSAIDs does not appear to be of prime importance in the pathogenesis of clinically important endpoints (symptomatic ulcers). The pathogenesis of symptomatic peptic ulcer disease caused by repeated exposure to NSAIDs is mainly a consequence of systemic (post-absorptive) inhibition of gastrointestinal mucosal cyclo-oxygenase (COX) activity. Even intravenous or intramuscular administration of aspirin or NSAIDs can cause gastric or duodenal ulcers in animals and humans [2].

PMIDs: 1 - 18242146 (“The incidence rate of peptic ulcer disease is similar in patients using low-dose effervescent calcium carbasalate compared with regular low-dose acetylsalicylic acid. This implicates that peptic ulcers seem to be related to systemic rather than to local effects of low-dose acetylsalicylic acid.”) 2 - 631484 (“These studies show that when the stomach is acidified by giving histamine intravenously or HCl intragastrically, intravenous aspirin produces large deep gastric ulcers.”)

The above is a partial paraphrase from UpToDate.

The regulators think, quite correctly, that people will generally take the dose on the bottle. If you only allow sales of Ibuprofen in 200mg pills and the bottle says “take two”, that’s what the vast majority of the public will do. If you allow sales of “ultra strength” 2000mg pills, a decent chunk of the population will take 2-4 grams because “ultra” must be better.

You can’t buy more than 2 packs of 200-250mg ibo in the UK at the time, and only one pack of anything higher, doses above 500mg require a prescription.

Prescription Ibo can be 2000-5000mg per pill so yes it does reduce the risk.