They do not allow a save
Only three examples of medicinals were given so far, Analgesic, Antitoxin and Sedative. Analgesic has a negative effect (you become flat-footed) along with it's benefit (bonus on saves against pain). Antitoxin has no negative effect, only a positive one (bonus on saves against poisons). Sedatives cause non-lethal damage when injected, along with a bonus against emotion and fear effects.
With that said, only the Analgesic really sounds like it could use a saving throw. But keep in mind that not all negative effects will allow saving throws, like certain abilities that must hit a target.
Sedatives are only strong on higher tiers, and they cost a fortune for single-use damaging items. If your purpose was to kill/incapacitate your target, there are far better choices. The item's description is pretty clear that they are used when you want to bring the target alive. If you have to pay 150 credits for 1d4 nonlethal damage, you are much better buying a Flare Gun for 1d3F for 90 credits and a couple of flares for 5 credits each.
Finally, at tier 4 they cost 23,500 credits and cause 4d4 nonlethal, that's insanely overpriced. You could buy an Aurora Arc Rifle for nearly the same cost that causes 2d12 stun damage and can fire 40 times before you have to reload it with a new battery (330 credits).
Just remember that medicinals, unlike drugs, do not cause addiction.
I expect, in the future, if more medicinals are released, that some of them could have a saving throw. But since their description is that they are (mostly) beneficial drugs that do not cause addiction, it sounds like that not allowing a saving throw is supposed to be their difference.