The Bolivar isn't freely convertible except on the black market so there isn't any market (from free or otherwise) to talk about.
How it works is pretty simple. A connected businessman applies to the government to import medicine at the official exchange rate. He then takes those USD and contracts with a shell company he controls in Panama to buy antibiotics and provides all the paperwork. A small amount of those funds are then used to buy antibiotics on the open market and ship it to Venezuela. The profits are distributed around to othe shell companies controlled by various government officials to keep access to the favorable exchange rates.
Once they arrive in Venezuela the local paper writes up a story about the shortages and mentions the connected businessmen and officials as heros for importing needed medicine. Pictures are taken showing them inspecting the cargo as its offloaded.
But it there is still money to be made! Prices on antibiotics are regulated so a lot of the shipment is diverted into the black market which siphons up bolivars at the black market price.
Those are then traded back at the official favorable rates and the process repeats.
It's a brilliant scheme because the masses don't understand enough to understand how they are being robbed. Pick their pockets and then blame it on the "market" or "imperialist." Doesn't really matter as long as its a convenient.
And it gets better! Eventually things get so bad that people start sending relief supplies and cash which creates new opportunities to loot.