Three of the four major drug stores in Harvard Square were selling a high potency vitamin pill earlier this week despite a Food and Drug Administration ruling that the drug contains dangerous amounts of vitamin A.

The FDA ruling states that vitamin pills containing more than 10,000 units of vitamin A can be sold by prescription only.

"Myadec," a Parke-Davis vitamin pill containing 25,000 units of vitamin A, was on sale Monday and Tuesday at College House Pharmacy and was also available at Billings and Stover, Inc., and at Colonial Drug.

The drug stores are being permitted to deplete their stocks of drugs labeled before October 1. All three of the stores reported Monday that they had only a few bottles remaining on the shelves.

Recent FDA research using high dosages of the vitamin produced brain damage in test animals. In addition, hemorrhages and loss of hair have afflicted patients receiving in excess of 100,000 units a day, but the condition is rare. The FDA's recommended adult dosage is 5,000 units per day.

The vitamin pill was being sold in most places without any warning as to possible side effects or notification that it had been officially pulled off the market.

Francis A. Boyle, a graduate student who tried unsuccessfully to return his bottle of Myadec to College House Pharmacy when he realized that the pills contained too much vitamin A, said Monday he was going to file a complaint with the FDA.

He said the pharmacy was "highly unethical" in selling the pills without a warning.