Yes you are. Your decision to deny others access to the life-saving drug has led to their death. But how serious is your responsibility from a moral point of view? That depends on the circumstances. Perhaps the medicine was in short supply and you needed what you had for your own survival or that of your family. In this case, I think you did nothing wrong. Or perhaps the medicine was in short supply and you chose to give it to those who could pay you the most. This way of rationing your supply is not beyond moral criticism, but at least your drugs saved as many people as possible and so your conduct did not increase the number of deaths beyond what was unavoidable.

Now consider drug companies in the real world. They patent their medicines and then enjoy exclusive rights to sell them at monopoly prices, which can be 400 times higher than the marginal cost of production. There are generic producers in developing countries which produce much cheaper versions of the same drug for sale to the poor. But the large pharmaceutical companies and their governments, through treaties and law suits, are working very hard and quite successfully toward suppressing the production and sale of generic versions of drugs still under patent. Millions are dying as a result.

The justification offered for such conduct is that inventor firms have a right to their intellectual property in the invention of a new drug. If the right here invoked is the legal right, it won't settle the issue, which is whether the creation and enforcement of such legal rights is morally justifiable. Is there then a moral right to exclusive ownership of intellectual property? Think about it: If you and your partner had invented the Tango, would it have been wrong for any of the rest of us to copy your dance without your permission? And, if you believe there is such a moral veto right, do you think it would have the exact same 20-year expiration date as is enshrined in patent law? Most defenders of patent rights would not make such extravagant claims. They would instead appeal to the social utility of the patent system, which encourages the development of new medicines. But this appeal runs afoul of the fact that the majority of humankind cannot afford drugs under patent. By suppressing poor people's transactions with the manufacturers of cheap generic drugs, our governments and pharmaceutical companies are causing many of them to die for the sake of gains (incentivizing drug development) that benefit only to the rich.

Must we then, in order give the poor access to new medicines at competitive market prices, take away the incentive to develop new drugs? We must indeed take away THIS incentive: monopoly pricing powers. But we can still incentivize drug development in other ways, for example through an arrangement under which governments would reward inventor firms in proportion to the health impact of their invention. Under such a scheme, we taxpayers would pay some money to drug companies for any new and effective medicines they invent. But we would also benefit through lower prices for drugs and medical insurance, because any newly invented drug could immediately be produced by generic manufacturers, so that its price would be just slightly above its marginal cost of production.

Because such alternative schemes for incentivizing the development of new drugs are readily available, we are indeed morally culpable for killing millions of people in the developing world by making existing and effective life-saving medicines unaffordable to them.