What is an acceptable therapeutic index for approval by the FDA?

The FDA should publish Therapeutic index (TI) values for all drugs but they do not. Therefore it is not possible to know what the FDA considers acceptable. The therapeutic index (toxic dose/effective dose) should not be less than 1 because a drug should have beneficial actions at the same or lower plasma concentrations that cause toxicity. However, cytotoxic drugs to treat cancer, by definition are toxic in order to do their beneficial action of killing rapidly dividing cells. Therefore a therapeutic index of 1 is not unusual for a chemotherapy drug. Most drugs have a therapeutic index of 2 or higher. A TI of 2 is a dangerous drug and the patient must be watched carefully for signs of toxicity. Drugs with a TI of 5 or 10 are safer drugs. Some drugs with great selectivity and minimal toxicity have TIs of 50 to 100. These can be given as on large dose that will continue to work well for several days but drugs that can be used this way are unusual, like a few of the antibiotics that kill prokaryotic bacteria but have little or no effect on eukaryotic human cells. The most serious problem we are facing in medicine today is the use of many drugs together (polypharmacy) that make any drug with a low therapeutic index far more danger. Interactions that raise plasma concentrations of low TI drugs can be lethal even if the drug interaction is a C or D level interaction and not the X level drug interactions that are typically monitored. Far too many people die or are seriously harmed due to drug interactions with drugs having low therapeutic indices of approximately 2. We need to get the FDA to publish all of the TI values. The drug database companies would like to publish these numbers to improve patient safety. Without TI values, electronic record and CPOE systems are not reducing patient deaths or lower health care costs.