A recent study published by the Journal of the American Medical Association revealed that many drugs are approved and released for use before data is collected on how they compare with existing alternatives.

Joshua Gagne, the author of the study, is a pharmacist at Harvard Medical School in Boston. He and his colleagues researched the public data on 197 drugs approved by the FDA between 2000 and 2010. They discovered that a gap exists between the time the medicine is released and the time the data is available.

According to the study, an average of 70% of all market-approved medicines have comparative data available. This leaves a full 30% that do not have any comparative data to determine if the drug is actually more effective than other alternatives. This percentage, when broken down into therapeutic groups, varies widely. Only 33% of hormones and contraceptives have comparative data, while the average increases to 89% for diabetes medications.

Comparative data often takes several years to collect and report. Dr. Robert Temple, the director of the FDA’s Office of Medical Policy, is impressed with the number, stating that the average is quite high considering that no requirements are in place for comparative data.

Dr. Alec B. O’Connor at the University of Rochester School of Medicine and Dentistry has a different opinion. He calls the figure “sad” and says that he believes that news drugs should always be tested against approved alternatives. Otherwise, he stated, doctors are just guessing at whether it’s better or not.