Can't help on the motion sickness, but for altitude, acclimatisation is key.
You can take diamox (Acetazolamide) starting 24 hours before (for a total of 3 days), to help acclimatize... but acclimatization is the only real solution.
Be cautious, diamox has some pretty serious side effect on some people, so testing it before you travel is important. No doctor in Switzerland will prescribe diamox without a "test run" where you take it safely at home, and if there are any side effects you have the Swiss medical system to support rather than some remote mountain hut.
Oh yes, and (in Switzerland) diamox is prescription only.
Also - we need to put "high altitude" into context. Anything up to 2000 isn't high altitude. 3000 is moderate. 4000+ is ok. 5000+ is high altitude. For me. For everyone, it's different.
Some background:
At 5500m atmospheric pressure is about 50% of sea level pressure. The result is less oxygen getting into your blood, which will deprive the body of adequate oxygen supply (Hypoxia).
With time your body has a variety of ways it can acclimate to lower air pressure to avoid hypoxia - ranging from increased respiratory rate (2-3 days) to increased oxygen-carrying haemoglobin in the blood (weeks) to increased capillary density (weeks to months).
If your body experiences a sustained period of hypoxia the veins in your brain begin to dilate causing fluid to leak into your brain (Cerebral Edema). The increased intracranial pressure will initially cause headaches, nausea and blurred eyesight. Eventually, it will cause the brain to herniate most likely killing you.
Conversely, the veins in your lungs constrict, causing them to leak fluid which accumulates in the lungs (pulmonary oedema). Initially, this could exhibit as a cough or wheezing. Eventually, it will cause respiratory failure and very quickly after that death.
Diamox can speed up part of the acclimatisation process but are limited in how much they can do. Respect the altitude and listen to your body. Understand the symptoms and then be prepared to seek lower altitude if things are going tits up.