President Obama on Tuesday shortened the prison sentences of nearly two dozen drug convicts, including some given life in prison for their crimes.

The White House said the action continued Obama's effort to reduce harsh sentences imposed under outdated guidelines, a step that could lead him to use his powers to grant clemency more often in the final 22 months left in his term.

Neil Eggleston, the White House counsel, said many of the 22 people whose federal sentences will be cut short by Obama's action would already have served their time and paid their debt to society had they been sentenced under current laws and policies.

"Because many were convicted under an outdated sentencing regime, they served years -- in some cases more than a decade -- longer than individuals convicted today of the same crime," Eggleston said in a post on the White House blog.

He said the commutations granted underscore Obama's "commitment to using all the tools at his disposal to bring greater fairness and equity to our justice system."

With those granted Tuesday, Obama has now approved a total of 43 commutations. A commutation leaves the conviction in place and ends the punishment.

Eggleston said that Obama's predecessor, George W. Bush, had commuted just 11 sentences during his two terms.