Zidovudine and alovudine as cross-wise recovery internal standards in microdialysis experiments?

The study investigates the recovery over the dialysis membrane in microdialysis probes of two thymidine analogues, alovudine and zidovudine, in both the brain and white (epididymal) adipose tissue. There were no significant differences in recovery between the two compounds in neither tissue, but when dialysis probes are perfused with both compounds simultaneously the recovery of alovudine in the brain is reduced from 10.6% to 8.7% with 4-mm long, 0.5-mm diameter probes perfused at 1 microL/min. It is concluded that the substances can be used as internal standards cross-wise in adipose tissue while they are less suitable in the brain.