WASHINGTON — President Obama on Tuesday shortened the prison sentences of nearly two dozen drug convicts, including eight serving life in prison, in an act the White House said continues Obama’s push to make the justice system fairer by reducing harsh sentences that were handed down under outdated guidelines.

The effort could lead Obama to grant clemency more often as his second and final term in office winds down.

In December, Obama issued his first round of commutations under new guidelines that were put in place to cut costs by reducing the growing prison population and grant leniency to nonviolent drug offenders sentenced to yearslong terms of confinement away from society. A commutation leaves the conviction in place and ends the punishment.

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 the debt they owed 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“Because many were convicted under an outdated sentencing regime, they served years – in some cases more than a decade – longer than individuals convicted today of the same crime,” Eggleston said in a post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. The 22 individuals were sentenced between 1992 and 2006.

Eggleston said Tuesday’s commutations underscore Obama’s “commitment to using all the tools at his disposal to bring greater fairness and equity to our justice system.”

Obama has now approved a total of 43 commutations during more than six years in office. Eggleston noted that Obama’s predecessor, George W. Bush, had commuted 11 sentences during his two terms.

In a letter, Obama urged each individual to take advantage of the second chance he is giving them. The White House said it was the first time Obama had sent such letters.