More than 97 percent of the region's pharmacies closed for the day. The businesses are owed $600 million by the government, Think Spain reported.
A previous strike by pharmacies was effective, pushing the government to pay $150 million. But that settled the bill through January and the pharmacies have not received any payments since.
Some pharmacies are running out of medications, forcing customers to search from store to store to get their prescriptions filled.
Wisconsin business offering 'therapeutic cuddling' forced to close
Exploding whale video goes viral on Internet