Philadelphia ? Alcoholics and people who drink too much now have a new option to try to quit: a once-monthly injection of a medicine that cuts the craving for alcohol.

The drug, Vivitrol, is an extended-release injectable form of naltrexone, which has long been sold as a daily pill.

Vivitrol works by blocking neurotransmitters in the brain believed to be associated with alcohol dependence, diminishing the craving for alcohol. It is approved by the Food and Drug Administration for adults who are able to abstain from drinking alcohol in an outpatient setting, and are not actively drinking when they begin treatment.

Researchers at the University of Pennsylvania have studied naltrexone for more than two decades in suppressing cravings for alcohol and other substances, including opiates.

The once-a-month intramuscular Vivitrol shot will cost $695.