The federal government has stopped reimbursing a Miami doctor who wrote nearly 97,000 prescriptions for mental health drugs - such as antipsychotics - to Medicaid patients over 18 months, the Associated Press reports. And the case has prompted Chuck Grassley, the Republican Senator from Iowa, to call for a nationwide investigation.

Fernando Mendez-Villamil wrote an average of 153 prescriptions a day for 18 months ending in March 2009, according to Grassley. That’s nearly twice the number of the second highest prescriber in Florida, who wrote a little more than 53,000 prescriptions, according to a list compiled by state officials, the AP writes.

Grassley, who is a ranking member of the Senate Finance Committee, which oversees Medicare and Medicaid, sent a letter this week to the Department of Health and Human Services asking for a probe into top prescribers. HHS tells the AP they were aware of Florida’s high prescribing docs and are working with the state and federal agencies that investigate Medicaid fraud.

Most docs near the top of Florida’s list are in the Miami area, where Medicare fraud totals over $3 billion a year, higher than any place else in the country, the AP writes, adding that the drugs Mendez-Villamil, a psychiatrist, prescribed often included Seroquel, Zyprexa and Abilify.

Some docs on the list have multiple practices with other prescribers using their license, which is legal, Karen Koch, vp of the Florida Council for Community Mental Health, tells the AP. The state also has a shortage of psychiatrists, meaning a smaller number of docs are each serving more patients. And sometimes patients doctor shop hoping to sell drugs, which also drives up prescription numbers.

Seroquel is the only drug that has street value in the US. “When snorted, it acts like cocaine,” Koch tells the AP. The others “have high street value in South American countries because it is not available there so families in the U.S. are always trying to get it for their relatives there.” A spokesman for Florida’s Attorney General tells the AP there is a pending investigation into Mendez-Villamil.

A Florida doc who prescribed antidepressants to a 7-year-old foster care boy who killed himself in April is also on the list. The drugs carried a black box warning indicating they can cause suicidal thoughts and are not approved for young children. According to the report cited by the AP, Sohail Punjwani, who wrote 10,150 scripts during the same two-year period, was on the high-prescriber list several times but never sanctioned. He did not respond to the AP. The boy’s death prompted debate at the state’s child welfare agency about stricter rules for prescribing the meds to foster children.