ABSTRACT
For those excipients that are intended for use in inhaled or intranasal products, it is obviously necessary to conduct the bulk of the safety-testing program by the intended route of administration (e.g., inhalation and intranasal). Information by other routes can also be useful, but should be considered supplemental. For example, often those excipients that are given by inhalation have a significant oral component; therefore, oral toxicity data are useful and necessary in assessing safety. Similarly, toxicity information by the intravenous route can be useful when the excipient has a significant pulmonary exposure and crosses the lungs quickly and intact. Intratracheal studies can also be useful in preliminary screening studies, especially if test material quantities are limited or inhalation facilities are not available. However, the best and most relevant information is usually obtained from exposure systems that most closely mimic the intended route of exposure. This would include testing the product as a whole, including all excipients and drugs in one formulation delivered to the test species in the same manner as it will be with human exposure. However, this is not always possible and it may be desirable to test the excipient in a stand-alone situation to produce safety data on an excipient for use in many different products.
