Severe drooling with travel

My 2year old rescue has profuse drooling with travel. A 10 minute ride to the vet just barely starts it up. A 9 hour trip , it started a little over 10 minutes in and didn’t stop until we got to our destination. I was told she drooled when traveling by the rescue org, and so I asked for a med to help her on her first visit to the 10 minutes away vet. She was given Cerenia 180 mg 60 # dog. (Only took the one pill before travel)which had been used on a prior dog for stomach upset. I gave the pills from the current vet 2 1/2 hours before we actually left on the trip. She soaked a mat for a large kennel and a large beach towel from all the drooling. She looks anxious and or distressed to me but has had no retching or vomiting .she wouldn’t eat but did drink water midway through the trip 3 days ago, When I called the vet office, another vet was there and relayed thru the vet tech for us to buy otc meclizine and give her 100 mg. I know dogs metabolize meds differently than humans but she’s not dizzy, woozy, retching or throwing up. Just seems totally stressed even from getting into a car and I’m asking has anyone given their dog that much meclizine for drooling and did it help ?