No. This is like if my car engine broke (I have never even opened the hood of a car) and used a wikiHow to try and fix it. Then drove it 90 miles down the highway. Instead of the more costly going to someone who has been working with cars for years and buying a few new parts.
In other words, im going to likely get myself or others hurt and possibly even myself killed.
How do you even know it's specifical diphenhydramine?
This is like trying to put together a puzzle without any idea what the picture is. And if you mess up you could die or end up with thousands in medical bills