For equipment infrequently used to manufacture materials for research, toxicity studies, or Phase I clinical trials materials, how detailed should the cleaning validation be or is visual examination sufficient when toxicity is often unknown?

Section 19.3 says “During all phases of clinical development, . . . procedures should be in place to ensure that equipment is calibrated, clean, and suitable for its intended use”. APIs for clinical trials are usually produced in laboratory glassware and small-scale equipment that is easily disassembled, cleaned and inspected. In such situations, visual examination may suffice. Cleaning validation is really not an expectation at that level but, obviously, cleaning verification would be appropriate.