In this article, the authors have provided child psychiatrists with cytochromal concepts, illustrations of common CYP-based drug interactions, and CYP tables. Clinicians can use these tables to anticipate drug interactions. If two medications are listed on the same CYP, a drug interaction may occur, and depending on whether they are substrates, inducers, or inhibitors, clearance of one or both drugs may be altered. Because new information about CYPs rapidly becomes available, however, CYP tables have a short shelf life. To further predict and reduce the consequences of CYP-based drug interactions, child psychiatrists can limit their own formularies and review PubMed, Ovid, or other literature tracking programs each time they use two or more drugs (including nonpsychiatric ones). The following Internet websites can provide current CYP data: CYP charts http//:@www.dml.georgetown.edu/depts/ph armac ology/clinlist.html http//:@www.accp.com/p450.html CYP drug interaction program http//:@www.mhc.com/Cytochromes/ AIDS drug interactions http//:@www.tthhivclinic.com/interactions.htm http//:@www.fda.gov/oashi/aids/pitabv. htm l http//:@HIV.medscape.com/Medscape/HIV/DrugInteract+ ++ ion s/index.html http//:@www.hopkins-aids.edu/geneva/hilites_f le x_d rug.html.