The CO2 breath tests as monitors of the cytochrome P450 dependent mixed function monooxygenase system.

The CBT and ABT are simple to conduct and are sensitive, reproducible monitors of hepatic enzyme function. They monitor functional hepatic mass at the time the tests are conducted and are specific monitors of P1-450 and P-450 function. In the animal model, the breath test can be conducted repeatedly, thus making it easier to monitor hepatic enzyme function throughout the animal's development, during pregnancy, or before and after administration of xenobiotics. Because of this, the breath test requires fewer animals and less technician time than standard in vitro assays and reduces costs. The breath tests' simplicity, noninvasive nature, and safety (especially the CBT) combined with a high degree of sensitivity and reproducibility make them ideal for nontherapeutic clinical research in large numbers of humans, particularly in the pediatric patient, where risks must be almost negligible. The breath tests are especially well suited for the examination of the many-faceted relationships between xenobiotics and MFOS, and in particular those correlations which are unique concerns of developmental pharmacology and toxicology.