Hate to break it to you, but 50mg is pretty much a common dosage for most people taking Diphen. At least where I lived over the past few decades... This is mostly due to the effect of 'if 1 pill is almost enough to do the job, then 2 pills should be adequate'. You see this a lot with people who take Tylenol and/or Advil. Tylenol overdoses are more common because of the frequency of acetaminophens use in other medications in combination with people taking Tylenol not realizing they are doubling/tripling their doses.

So having people end up driving on 50mg+ doses of the dryl is not uncommon in places like Canada. Pair it with a dose or two of pseudoephidrine hydrochloride as well, and you basically have a breath easy cocktail that might put you to sleep, or might keep you awake all night.