Suicides involving firearms are fatal 85% of the time, pills less than 3%.

[FarCenter]

65. Prescription Painkillers Now the Leading Cause of Accidental Deaths

Car accidents are no longer the leading cause of accidental deaths in the United States. According to a recent report published by the CDC's National Center for Health Statistics, this dubious distinction now belongs to drug poisoning. What's at the root of this trend? A river of prescription painkillers.

Indeed, the report suggests that the United States is in the midst of a painkiller epidemic. Every year, more people now die from analgesic pain relievers, such as OxyContin and Vicodin, than cocaine and heroin combined. Abuse is so bad these days that doctors are having difficulty keeping up with the demand.
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The change atop the accidental death leaderboard officially happened back in 2008 when over 41,000 Americans died as a result of poisoning, compared to 38,000 vehicle traffic deaths. Of those, 90% were caused by drugs. It marked the first time since 1980 that car accidents were not at the top of the list.

There's little doubt that deaths by vehicle accidents are on the decline, but it does not compare to the sharp rise of poisonings. During the past three decades, the poisoning rate has tripled from where it was in 1980, while motor vehicle deaths decreased by almost one-half over the same time. And from 1999 to 2008, the poisoning death rate increased 90%, while the motor vehicle traffic death rate decreased 15%.

Looking at the period 1980 to 2008, the percentage of poisoning deaths caused by drugs increased from 56% to 89%. Of the poisoning deaths that happened in 2008, about 77% were unintentional, 13% were suicides, and 9% were of undetermined intent.

I'd bet that a lot of the "accidental drug poisonings" were actually successful suicides. If you use a gun, it's usually clear that you committed suicide, although there are a lot of "cleaning his gun and it accidentally went off" cases that are pretty dubious. However, with drugs, it is a lot harder to establish intent, unless there is a note or the person is found conscious by someone and later dies.