A study was published in 2017 about the anti-inflammatory asthma drug montelukast and Alzheimer's prevention using the Norwegian Prescription Database. The study compared medical records of elderly asthmatic patients who took montelukast (one 10 mg tablet a day) with records of those elderly asthmatic patients not taking this drug. The results showed that the number of those patients who were taking montelukast who were later diagnosed with Alzheimer's was slightly less than the number diagnosed who were not taking the drug. The difference was statistically significant but still small.

Montelukast has to pass through the blood brain barrier, and I have to wonder if 10 mg a day is enough. I myself am taking 10 mg three times a day, which seems to work best for me. Intelgenx, a small pharmaceutical company, has chosen the FDA approved 10 mg a day dosage for their montelukast Alzheimer's trial so it won't have to pay for additional safety trials for higher doses, which would cost millions of dollars more. If a major drug company were sponsoring the trial, it would have the money to pay so they could have better chance of getting positive results. Unfortunately the major drug companies are not interested in generic drugs with low selling prices.

So what happens if the montelukast trial shows a slight improvement at 10 mg a day with Alzheimer's patients, but it is not enough for the FDA to approve it as a treatment. Does Intelgenx have to start over with an addition safety trial to increase the dosage, costing much more money, or would the FDA allow them to increase the dosage in the ongoing trial. Do we have any FDA clinical trial experts out there? 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5579921/#!po=95.5357