Toxicity testing of polymer materials for dialysis equipment: Reconsidering in vivo testing

The rationale for preclinical testing of plastic materials for medical devi ces is the protection of patients from leachable toxic substances. A contro versial and costly part of this testing is the use of animal in vivo proced ures. The objective of the present study was to analyse the importance of i n vivo tests in relation to the decision to approve or not to approve mater ials for use. A total of 1044 plastic materials were analysed by employing chemical, in vitro and in vivo tests: 5708 in vivo tests were performed. In only one out of 2650 systemic injection tests on mice did a material fail. As that material also failed in chemical tests, the systemic injection tes t had no influence on the decision not to approve the material. Intradermal irritation (2644 tests), implantation (398 tests) and sensitivity (11 test s) procedures on rabbits and guinea-pigs were the other in vivo tests. Howe ver, in ail except three cases, the same decision on whether or not to use a material would have been reached without any of these in vivo tests. Thus , little security appears to be gained from the in vivo tests, and abandoni ng them would save resources, probably without any additional risk.