Of the 36 states, and the federal government, that use lethal injection, most use the same method that Ohio has now abandoned: a three-drug combination of sodium pentathol, pancuronium bromide and potassium chloride. The latter two drugs serve to paralyze the inmate and then stop his heart.
Ohio had problems with the standard method, failing to execute a prisoner "after 18 puncture attempts," so they went with the simpler option of a single lethal dose of an anesthetic.
In my opinion lethal injection is an unnecessarily complicated method of execution. There have been a number of problems with it, not just in Ohio, partially because doctors can't be involved in the actual execution. You have people that aren't well-trained attempting to find suitable injection sites, and sometimes botching it. With the minimal number of people actually executed in the U.S., there is just no need for complicated, inefficient and expensive methods of execution. A rope attached to a gallows is a quick, cheap and effective method of eliminating the few criminals who actually manage to make it all the way to an execution date. It was used throughout much of U.S. history and there was really no good reason to look for other methods. And there are other simple types of execution, such as death by firing squad. There is no need for things like electric chairs, gas chambers, or lethal injections. Let's bring back the gallows.