What's the highest dose of dimenhydrinate that can be taken? if i'm on a cruise & took 100 mg & it's not helping, would it hurt to take another 50 mg?

Dimenhydrinate: For an adult, 50 to 100 mgs can be taken every 4 to 6 hours, but bear in mind that mixing this medication with alcohol or many other medications increases the potential for side effects. Drug abusers take many times the recommended dose and incur hallucinations. I feel that factors like associated fever, alcohol intake, vigorous exercise can cause potentially severe side effects.