BOSTON When a patient isn’t showing a response to a medication, a common tactic the doctor might use is to increase the dosage. According to a new study, however, the ineffectiveness might be happening because the patient isn’t properly taking the medication.

The Medco Research Institute, the research arm of pharmacy benefit manager Medco Health Solutions, found that nearly one-third of patients given increased dosages of antidepressants were not regularly taking their original prescriptions. Data from the study recently were presented at the American Psychiatric Association’s 62nd Institute on Psychiatric Services in Boston.

Medco said the study showed doctors should monitor a patient’s adherence to their antidepressants before raising the dosage because poor adherence may contribute to disease relapse, thus leading to unnecessary dosage increases.

“A physician usually increases a dose when a patient is not responding to the current dosage,” Medco Neuroscience Therapeutic Resource Center national practice leader and lead study author David Muzina said. “But the analysis shows that the reason the dose may not be effective is that many patients are not taking their antidepressants as directed.”