Lithium is a naturally occurring substance so it is not possible to patent it. In consequence, there is no way of recovering any investments in working out how to handle its sometimes toxic side effects.
The first patients treated with lithium in 1949 were well within 2 weeks. Their discharge from the asylum where they had been living for years was delayed for a couple of months just to make sure that the medicine lithium was actually working. It was such a stunning success that their doctors had to check. The inability to patented lithium delayed its commercial availability by over two decades.
From Wikipedia at https://en.wikipedia.org/wiki/John_Cade