Washington (AFP) - US regulators have approved the first pill that contains a digital tracking sensor to alert doctors and caregivers as to whether a patient is taking the medication as scheduled.

The pill, called Abilify MyCite (aripiprazole tablets with sensor), is designed for patients with schizophrenia, bipolar disorder and depression, according to the US Food and Drug Administration.

A patient ingests the pill, and a sensor inside the pill activates when it reaches the stomach fluids, sending a message to a wearable patch.

This patch then transmits the information to a mobile app, so that a doctor and up to four caregivers, friends or family members can see the information through a web-based portal.

"Being able to track ingestion of medications prescribed for mental illness may be useful for some patients," said Mitchell Mathis, director of the division of psychiatry products in the FDA's Center for Drug Evaluation and Research, in a statement Monday afternoon.

"The FDA supports the development and use of new technology in prescription drugs and is committed to working with companies to understand how technology might benefit patients and prescribers."

Although the sensor can alert caregivers, the makers of Abilify, Japan-based Otsuka Pharmaceutical, said it is unclear whether the tracking device will actually help improve patients' ability to take their medication daily as prescribed.

The FDA approved Abilify in 2002 to treat schizophrenia, which affects about one percent of the US population.

The ingestible sensor used in Abilify MyCite was first allowed on the market by the FDA in 2012.

The sensor technology and patch are made by Proteus Digital Health, and are approved for use with existing medications in the United States and Europe.

But until now, the FDA had not approved a sensor-pill combination.

Some experts raised questions about the choice of Abilify as the drug in which to test the sensor, and the "Big Brother" connotations of being tracked.

"Patients with a tendency towards paranoia may feel a bit uncomfortable being monitored in this fashion," said Seth Mandel, chairman of psychiatry at Northwell Health's Huntington Hospital in New York.

"Patients with bipolar disorder and schizophrenia are very often non-compliant with their medication and the result is almost always a relapse," he added.

Still, he said the pill may "potentially be a significant advance in our never-ending struggle to improve patient adherence to psychotropic medication."

Scott Krakower, assistant unit chief of psychiatry at Zucker Hillside Hospital in Glen Oaks, New York, said more research is needed to see how the pill affects people in real life.

"This could be a really helpful device to help some of our patients," who often "have difficulty with focusing and concentrating and may forget to take their medications," he told AFP in an email.

"On the other hand, one of the goals we set for patients is to improve quality of overall functioning with their lives.

"In some situations it may hinder the autonomy some patients are working toward in their treatment, or it may enable patients to rely on an instrument instead of themselves for treatment."