Cassette dosing, combining many test chemicals into one dose solution, is an attractive method for increasing the throughput of in vivo pharmacokinetic experiments. This dosing technique depends on the sensitivity and selectivity of modern analytical techniques, particularly HPLC/MS/MS. Cassettes vary in size, but even relatively small ones greatly increase the numbers of compounds investigated by reducing the effort devoted to animal handling, sample processing and sample analysis. The major drawback of cassette dosing is the potential for drug-drug interactions.