Possible causes of treatment failure with the NSAID.

The clinical efficacy of non-steroidal anti-inflammatory drugs (NSAID) is often disappointing in spite of their well-known antiphlogistic actions. The reasons for this failure are probably due to irregular intake by patients on long-term treatment with such agents. These considerations inevitably point to the necessity of concomitant determination of the plasma levels of all NSAID tested, and the need to perform clinical trials in an appropriate setting in which such determinations can be conveniently carried out.