In recent years, there has developed the belief that nonproprietary or generic drugs are much cheaper than, and as effective as, trade-named items. This belief has led to a widespread demand that prescribing and use of generic drugs be encouraged. Studies conducted by impartial groups such as the Medical Letter on Drugs and Therapeutics have applied United States Pharmacopeial methods to assay certain drugs prepared by many different manufacturers.1-3 These analyses have shown that, generally, these preparations are chemically equivalent in that they contain the amount of drug claimed. These findings have led many to the conclusion that drugs prepared by various manufacturers should be equally effective in therapy. While this seems to be true in many instances, there are situations where this is not so.
For some time, workers in the pharmaceutical field have been compiling a list of factors which may influence the therapeutic usefulness of a