BACKGROUND: Systematic reviewing is a time-consuming and resource-intensive process. Information specialists are maintaining study-based registers to facilitate efficient conduct of systematic reviews. Classification of study-level meta-data -such as interventions -can result in much more accurate searches, saving time in the early steps of systematic reviewing. OBJECTIVE: To classify all pharmacological interventions from all schizophrenia trials. METHODS: We used Cochrane Schizophrenia's Study-based Register as the source of trials, Emtree and MeSH for synonyms, AdisInsight and CT.gov for research drugs and WHO ATC for marketed drugs. RESULTS: One third of tested interventions on patients with schizophrenia are pharmacological (816; belonging to 106 clinical classes) with antipsychotic drugs being the most researched (15.1%). Only 528 of these medications are listed in WHO ATC. Around one third of these drug interventions are seen only in research (236; from 21 pharmacological/biochemical classes). Within the pharmacological interventions, we identified 28 'qualifiers' including dose, route and timing of drug delivery. CONCLUSION: Identification and classification of pharmacological interventions from trials require use of many sources of information none of which are inclusive of all drugs. Limitations of each source are helpful to understand. Classification of non-pharmacological interventions is now a priority for clinical and information scientists and professionals.