Putting 2yo in front seat of car???

How unfortunate.

Can I ask how you drive? Heavy acceleration and braking? Or do you accelerate and brake slowly? I had someone drive me once and they were abrupt with everything. The car was nosing up with acceleration, nosing down on braking and heavily rolling in corners. I wanted to hurl. To check, put a basketball on your front seat. If it rolls off while you're driving, then you're too abrupt and need to practise until the ball doesn't move on the seat.

Other thought, fresh air is king when you feel nauseous, so try windows down.

Finally he may be making himself sick out of distress about getting in the car. Can you do a short trip without him being sick? If so, repeat many of those so he starts to get over the fear of being sick in the car.

Motion sickness herbal stickers for behind the ear. These worked absolutely brilliantly for my very travel sick kiddo. Used them and literally no more sickness, not even once. A sticker behind each ear, and they were an absolute miracle. They smell quite herbally. I recall they have an age lower limit so check on that!

www.amazon.co.uk/gp/aw/d/B01JCVJYL8?psc=1&ref=ppx_pop_mob_b_asin_title

Do you always catastophise like this and assume the worst? Because it’s most likely just travel sickness. If travel sickness remedies don’t work then maybe see a GP - but it’s still not an emergency. Does your child even have any other symptoms that would suggest it’s one of those other conditions? If so, that’s what we call a drip feed and really should have been in the OP. Obviously if your child has a shit load of other symptoms that suggests migraines or whatever you get them checked out - because for that you are looking for a diagnosis. Your op suggested you were purely concerned about travel sickness though, so I replied based on that.

The other thing we found was that once DD got to about 3, she got pretty good at catching her own sick. We bought these, which contain everything and are absorbent, and put a towel as a blanket over her in the car. We also tried to always have an adult in the back with her, but as im sure you've experienced, it does really limit you on a day to day basis.

https://www.amazon.co.uk/Medi-Grade-Vomit-Bag/dp/B082WH9G1B/ref=mp_s_a_1_4?crid=2R1PV4XZPPBOA&dib=eyJ2IjoiMSJ9.7-ihS3C-TgwbW3VztoX78jRI7e1u4T_cI6UDKryS9IO5JPzTsD6iaf2bktbzeiKoplalfir4DI2-cJFf502E4UgrukRpWWJDsYMRHAvGT_1HxU-aeOkkCTSC_W3WGOJBcSroeXdDReJNARdp2BVMdHvIQxfLNVa82NkMjyO49Z6rqdvEdROgmFjrLTzUl-tuJbTvu2mEyxx6J--M0DzzqA.IVYNADJt74vWS7LN4V51c5DWvJIsYdtQHHYY43EtQE0&dib_tag=se&keywords=sick+bags&qid=1757202963&sprefix=sixk+%2Caps%2C113&sr=8-4

I get that, but it’s not an emergency. I think you’ll get faster and better advice by talking to a pharmacist. They are MUCH more clued up than doctors about medications - a doctor is the person you would go to if you don’t know what’s wrong (or it’s something a pharmacist can’t prescribe you) to be diagnosed on the whole, if you know what’s wrong the issue is, go to the medication expert first!

Bless, you can only try.
I'd try him in the front and encourage him to look out the windscreen. Count cars, colours, anything to keep him looking forward
Put him as high as the seat goes and airbag on (off is only for rear facing).

While car seat safety is important. Its far more important that the driver (you / DH) isn't distracted by a puky child while driving. Minimise the risk of distraction and accident.

Its a long time ago but a friend was in a minor bump because a Mum being distracted by her child puking into a carrier bag.

I would try the piriton liquid first as you can take it from age 1, before ff in the front seat, which really is the worst option. My eldest DD (now 4y) has been travel sick since she was 6months old including on buses and trains. When I recently bought Kewells Kids, the pharmacist told me to not to give allergy medicine on the same day, as they both work in the same way. We've basically not driven anywhere for 3.5years so i wished id found out about it sooner! So it might be worth a try. On our recent holiday, we had a couple of non-negotiable drives and for the first time, she wasnt sick at all.

I've read that some parents can get medication from the GP earlier than age 4, so you could also ask about that at your appointment.

Where do you need to drive to?

I would only use the car if you absolutely have to if it's this bad.

There are a lot of travel sickness remedies that aren't pharmaceuticals. His might be too severe for this, but worth a try?

Green apples
Ginger - crystalline or in tablet form
Essential oils on pulse points (called Motion Eze or something like that? It's largely peppermint based).
Acupressure wrist bands.

That’s definitely incorrect. You can rear face but only if the airbags are turned off. However I do not think rear facing in the front will help him - he needs to be able to see out of the windscreen. Travel sickness is caused by mixed signals - what he is seeing isn’t matching with the speed/motion he’s feeling which results in sickness. It’s why they say don’t read in a car or look out of the side windows. Front window is the best way to stop the mixed signals.

My middle son has always had awful travel sickness. We found kids Kwells the best medication. We used the accupressure travel bands when little, but the last couple of years we use motion sickness patches - you stick one behind the ear and one above the naval and they work amazingly well!

I doubt a GP can or will do anything, and you don’t need an emergency appointment with all due respect - how on earth is this an emergency? You’d be better going and speaking to a pharmacist.

I also find that making sure they have something to eat before travelling helps more than an empty stomach.

Is it the rear facing movement that is making the sickness worse? How is he if forward facing?