Previous research has shown that patients take only about half of their prescribed medication, and a new study suggests that interventions designed to improve these rates have proven futile thus far.

The research, published in The Cochrane Library, draws data from 182 trials that tested various approaches designed to increase medication adherence, Medical News Today reported. When patients fail to take their medications as prescribed, they put their health at risk. In addition to not taking the full amount of medication prescribed, many patients fail to follow the instructions for taking their meds, past studies have revealed.

In the new study, scientists assessed trials that analyzed medical conditions as well as those that pertained to medication adherence plans. However, their review considered many studies that had underlying design issues, which made it difficult for researchers to pinpoint which intervention approaches were effective. Often, the researchers wrote, trial evidence was “unreliable and inconsistent.”

Many of the trails varied widely in terms of the number of patients considered, treatments, medicine adherence measurement and clinical outcomes.

“It would have been misleading to try to come up with general conclusions," lead researcher Robby Nieuwlaat, of McMaster University in Canada said in a statement.

Nieuwlaat and his team that only 17 trials were high-quality. The strong studies tested combinations of different approaches, such as education, counseling, and family and pharmacist support.

Only five of the trials indicated an improvement in patients’ health outcomes and increased medication compliance.

"It is uncertain how medicine adherence can consistently be improved so that the full health benefits of medicines can be realized,” the researchers wrote. “We need more advanced methods for researching ways to improve medicine adherence, including better interventions, better ways of measuring adherence and studies that include sufficient patients to draw conclusions on clinically important effects."

To help jump-start that effort, the study authors have created a database of the trials, which the medical community can review to develop better intervention plans.

"By making our comprehensive database available for sharing," Nieuwlaat said, "we hope to contribute to the design of better trials and interventions for medication adherence."

"We need to avoid repeating the painful lessons of adherence research to date and begin with interventions that have shown some promise, or at least have not produced repeatedly negative results.”