Where does a doctor's duty end?

Here are the sad facts of a fatal accident: An elderly man taking several prescription medications for several conditions lost consciousness while he was behind the wheel, killing a 10-year-old boy.

The boy's family sued the driver's doctor, saying he should have warned the man about potential side effects, but the case was dismissed. A higher court reviewed the dismissal, and a chill passed through the medical profession when these justices ruled that doctors must inform patients of side effects that could impair their ability to drive safely.

Well-known ethicist George Annas of Boston University says the Massachusetts Supreme Judicial Court's 2007 opinion "is not a model of clarity." Writing in the New England Journal of Medicine, he says he agrees with their finding but doesn't see the same cause for alarm that physicians expressed in a Globe news story and later health column.

Annas says doctors have an obligation to tell their patients about drugs they've prescribed for them that may affect how safely they drive, as most of the justices said. Fears of broadened liability are unfounded, he says, suggesting there are few physicians who would fail to advise patients about the dangers of driving while on certain medications.

"The majority -- rightly, I think - refused to exempt physicians from the ordinary standards of negligence that apply to everyone else," he writes. "And to the extent the opinion results in more explicit information about the risks of driving under the influence of prescription drugs, it is difficult to view this as a negative result."