Keith 1994

Methods	ITS with monthly data points
Participants	Texas Dept of Criminal Justice Institutional Division 1991: n=46,762, 1992: n=50,740
Interventions	Formulary H2RA program to limit duration of treatment dosages and promote maintenance therapy in appropriate individuals
Outcomes	Drug use, health services utilization, drug costs
Notes	Drug use evaluation (DUE) completed in May 1991, program implemented Nov 1991, follow‐up DUE completed in May 1992, no transition period
Risk of bias
Bias	Authors' judgement	Support for judgement
Incomplete outcome data (attrition bias) All outcomes	Low risk	Any undocumented difference in the proportion of missing data in the administrative datasets pre‐ and post‐intervention is unlikely to overturn study results Non‐prescription medication not maintained on automated system.
Selective reporting (reporting bias)	Low risk	All outcomes reported
Other bias	Unclear risk	Number of upper gastrointestinal studies decreased by 5.7% ‐ appropriateness of diagnostic studies unknown.
Knowledge of allocated interventions adequately prevented during the study	Low risk	Outcomes are objective measures of healthcare utilization Approvals done on automated system
Intervention independent of other changes	Low risk	Changes occurred in duration of inmate stays and total number of inmates (8% increase) however this would tend to produce an increase in the use of restricted drugs not a decrease as observed
The shape of intervention pre‐specified?	Low risk	The point of analysis is the point of intervention; ie, the date the policy intervention was implemented was used to delineate pre and post policy time periods with adequate data points to capture the shape of the pattern of intervention effect over time
Intervention unlikely to affect data collection?	Low risk	Sources and methods of data collection were the same before and after the intervention Pre‐defined criteria and authorization communicated by computer to regional pharmacies