Effect of blood microsampling (50 μL) on toxicological assessment in rats treated with tacrine, a drug known to have adverse effects that increase neutrophils.

To promote the 3Rs in toxicological assessment, the recommendation for blood microsampling in toxicokinetic evaluation is noted in the ICH Harmonized Guideline S3A Q&As. However, there are only a few articles reporting the practical application of microsampling in the toxicological assessment with toxic drugs. In this study, we investigate the effect of microsampling on toxicological assessment in rats treated with tacrine, which is known to have toxic effects that induce an increase in neutrophils and behavioral abnormalities. Thirty female Sprague-Dawley rats were divided into microsampling (MS) and non-microsampling (non-MS) groups, and orally administered tacrine once daily at dose levels of 0 (vehicle only), 3 and 10 mg/kg bw for 28 days (each group: n=5). In the MS group, blood samples (50 μL/time point) were collected at 6 time points on day 1 and 7 time points on day 28 to 29. All the animals underwent necropsy on day 29. By comparing the results of toxicological and toxicokinetic analysis between the MS and non-MS groups, we validated effects of microsampling for toxicological assessment. Although increase in neutrophils and repeated stereotypic behaviors were observed as toxic effects in the rats administered tacrine, we could not find any difference between the MS and non-MS groups, and also found that microsampling did not affect any other data from toxicological and toxicokinetic analysis. In conclusion, blood microsampling appeared to be a feasible technique for the toxicity study of tacrine and was considered to be applicable in the toxicity study of even drugs with toxic effects on hematological parameters, such as an increase in neutrophils.