Health Care in Cuba
There is one part of the Cuban government with plenty of dollars to spend on medical products - Servimed. Cuba has cradle-to-grave free health care for its citizens and about one doctor for every 200 people. Cuba has long been recognized globally for its excellent level of medical expertise and has traditionally sent doctors to serve for free to many developing nations as well as hosting patients from around the world to free medical care in Cuban facilities.
That charity work has now been converted into an important dollar-generating industry, "health care tourism." Patients from all over the world travel to Servimed-run facilities in Cuba for high-quality, reasonably-priced medical care, paying in dollars.
U.S. companies cannot obtain an export license to sell to Servimed, however. The U.S. seeks to regulate the trade of foreign companies with Cuba through "U.S.-content" regulations. Any foreign company who sells products with more than 10% U.S. content - which could include U.S. technology or a U.S. patent - must obtain an export license from the U.S. government.
This is especially powerful in the health care field since the U.S. is a leader in medical products and technology. But that doesn't answer the question of why there is such a severe shortage of medicine in Cuba. I think the shortest answer is that just because something is legally possibly doesn't mean it's easy or even that people know it's legal.
Political realities in the U.S. - predominantly on the East Coast - have created an atmosphere of enforced ignorance on the part of the government toward eligible businesses. The conventional wisdom holds that you can't do business in Cuba, period; and the government is not anxious to correct that impression, so many eligible businesses never bother to try.
The companies that do try often get bounced from congressional representatives to the State Department, to the Treasury Department, to the Commerce Department, receiving contradictory and often discouraging information at every stop before finally giving up. Foreign companies seeking licenses are especially vulnerable in this run-around. Companies are also extremely sensitive to any possible negative publicity in the U.S. about their dealings with Cuba, something that politically powerful anti-Castro Cuban-Americans are able to credibly threaten.
This has dramatically limited both the number of companies selling medicine to Cuba and the variety of quality of medicine available for purchase. And the Cuban government plays a role in shortages when other export goods, like oil, are deemed a higher priority for the use of scarce dollars.