A former Florida hospital official pleaded guilty in federal court in Alexandria yesterday to falsifying records that allowed 10 would-be physicians to buy bogus medical degrees from foreign medical schools.

Dr. Joseph D. McPike, former medical director of Polk General Hospital in Bartow, Fla., was charged in a scheme that federal prosecutors say was masterminded by Pedro de Mesones of Alexandria, in which 165 "checkbook doctors," most of them U.S. residents, bought phony medical degrees.

The scheme, which also has led to fraud charges in New York, New Jersey and Pennsylvania against nine persons who allegedly bought fake degrees from de Mesones, has shaken the medical community and sparked a reexamination of medical credentials from foreign schools.

Earlier this month, de Mesones testified before a congressional panel that concluded that as many as 10,000 U.S. doctors may have bogus credentials from foreign medical schools.

Assistant U.S. Attorney Theodore S. Greenberg said yesterday that five of the persons whose records McPike falsified had been practicing in U.S. hospitals, but have been dismissed.

It is not clear whether the other five, who have not been located, received medical degrees from the foreign schools, Greenberg said.

Court records show that from January 1982 to August 1983, McPike, who supervised undergraduate training for medical students at Polk, certified 10 students as having completed 15 months of clinical training. In fact, five of them had attended less than a year and the others never attended, according to the records.

McPike also is charged with forging signatures on some student records. According to court records, McPike's actions "permitted unqualified persons to graduate as medical doctors" from two schools in the Dominican Republic.

As part of a plea agreement entered in U.S. District Court in Alexandria, McPike pleaded guilty to three counts of mail fraud and conspiracy and was sentenced to two concurrent three-year sentences and fined $11,000 by Judge Richard L. Williams.

McPike, who was fired from the hospital a year ago, is serving a three-year sentence in Florida for grand theft arising from his acceptance of $13,750 from de Mesones for falsifying the student records. McPike was brought to court yesterday in the custody of U.S. marshals.

McPike's attorney, Thomas Anthony Durkin of Chicago, said after the sentencing that his client had made "some errors in judgment" and "wasn't in a position to keep up with all the students" at Polk.

De Mesones pleaded guilty last year to using the mails to solicit customers to whom he provided fake degrees from medical schools in the Dominican Republic, at a cost of up to $$27,000 each. He is serving a three-year sentence at the federal prison camp in Allenwood, Pa.

Federal prosecutors said that none of the 165 "doctors" who obtained false credentials from de Mesones was from the Washington area, and none practiced at hospitals here.