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Glaucoma drug trials: Why 349 trials and 130 unique interventions?

Date and Location




Saturday 21 September 2013 - 10:30 - 12:00


Presenting author and contact person

Presenting author

Tianjing Li

Contact person

Tianjing Li
Abstract text
Background: Theoretically, unlimited variations of interventions or combination of interventions can be evaluated in randomized controlled trials (RCTs) for a given condition, for example, by varying dose and usage, and by combining one drug with another. However, not all interventions may pan out as worthy and ethical pursuits. Objectives: To examine the history of glaucoma drug trials and to explore factors contributing to “isolated” trials, defined as single trials evaluating interventions not evaluated in any subsequent trial for the condition. Methods: As part of a network meta-analysis, we examined the number of times an intervention was evaluated in RCTs of medical treatment for glaucoma. We are in the process of comparing the characteristics of “isolated” trials with other trials, and examining factors (e.g., sponsorship, statistical significance and direction of results) associated with the frequency that an intervention was evaluated in RCTs. Results: We included 349 trials on glaucoma medication published between 1966 and 2009 (median 2001). These 349 trials examined 130 unique interventions; 62/130 (48%) interventions were examined in only one RCT. These isolated interventions were largely drugs not typically used for glaucoma (e.g., celiprolol), non-standard dosages (e.g., timolol 1%), or two drugs used as a combination therapy (e.g., dipivefrin 0.1% and levobunolol 1% used together). The combination therapies constituted more than half of all isolated interventions. Conclusions: Examining any trial in the context of the entire evidence base provides an opportunity to investigate factors that may contribute to selecting interventions in RCTs. Curious investigators may test drugs off-label, at a different dose, or in combination with other drugs to explore potential benefits to patients. Alternatively, if trials are initiated for marketing purposes or a way to obtain a publication, which are of little relevance or value to patient care, recent claims of avoidable waste in clinical research ring true.