As indicated previously, there are regulatory guideline requirements (stated or implied) for in-use stability testing, but there is no regulatory guidance on how to conduct this test in the human medicinal product sector. It would be of great assistance to manufacturers if the regulators would consult on proposed guidance, propose data that they would like to see and define the type of studies that they would find acceptable. However,in devising the guidelines it is essential that due consideration be given to the practicalities of actually conducting the test.In particular, the restrictions on conducting such tests with small-volume liquid dosage forms should be taken into account. In these cases, the availability of sufficient product for testing is severely limited, especially if the recommended frequency of dosing is relatively high.