When Mainers turn over thousands of pounds of unused and unwanted prescriptions Saturday, a small army of University of New England pharmacy students will be on hand at several drop-off locations.

Their mission is to count each different medication to see which are wasted most often.

“If you can look at the percentage of waste, then you start asking why,” said Heather Stewart, who is earning her doctor of pharmacy at UNE, and the answers can lead to improved practices that reduce waste.

Stewart’s research is jeopardized by a Drug Enforcement Administration rule now under consideration. The rule is aimed at protecting the drug take back program from diversion by ensuring that only law enforcement is allowed to handle the medications, some of which are highly sought after by addicts.

However, that would shut out data collection efforts in Maine and the nine other states where such analysis is ongoing.

Sen. Susan Collins, R-Maine, has weighed in on the issue, sending a letter to DEA Administrator Michele Leonhart arguing that such data collection is important for developing policies to reduce costly waste of prescriptions. There have been no episodes of diversion in Maine during the data collection, she said. She urged the agency to reconsider.

Pharmaceutical Research and Manufacturers of America, a leading industry grade group, in its comments on the proposal also supports local collectors gathering information on the medications collected in the take-back programs to inform prescribing practices to reduce waste.

DEA is still fomulating the rules, and it’s uncertain what they will contain and when they will take effect.

Stewart’s research so far has found that the largest single class of unwanted drugs being disposed of is cardiovascular medicine for conditions such as high blood pressure and clogged arteries.

Of 375,674 medicine doses — primarily pills — counted from three take-back events, 11 percent fell into that category.

The analysis also found that those medications showed one of the highest level of waste. More than 79 percent of the original prescriptions of those medications were left over.

Gastrointestinal, antidepressant and asthma medications that were turned in all showed more than 80 percent of the prescription left over.

“Now that we have an actual concrete number of what’s coming back, we can start figuring out how to change it,” Stewart said.

Surveys indicate that 27 percent of the unwanted medications were discarded because a doctor said to stop taking them. Almost 20 percent belonged to a patient who died, 18 percent because the person no longer needed it, and 12 percent because of a negative reaction.

Stewart has presented her data to state boards and working groups studying prescription drug diversion.

Reducing waste would mean less medication being flushed down the drain and entering the environment. It also would mean less leftover pain medication, which is particularly prone to abuse by young people, which can lead to addiction.

From a health policy standpoint, the results could save insurance companies and MaineCare, the state’s version of the federal Medicaid program, money if it results in prescription practices that lead to less waste.

In her letter to the DEA, Collins said earlier data from the state’s mail-in drug collection effort, which no longer exists, led to changes in MaineCare prescription drug coverage that reduced the number of doses when a person first tried a medicine. That way, if it didn’t work, there was less waste.

Stewart is working to spread the word about her research to health care providers and state policymakers.

On Thursday, she was driving back from the Maine Nurse Practitioner Association in Northport, where she answered questions about the data. Last year she was invited to Greece — which has a serious prescription waste problem — for an international environmental conference.

Maine is a great laboratory for the analysis.

Since the DEA-led drug take back effort started in 2010, Maine consistently has led the nation in the amount of drugs returned per capita.

The volume of drugs disposed of in the take-back effort grew steadily from 7,820 pounds at the first one in 2010 to 19,980 in the spring of 2012. Collections dropped off to 13,980 pounds in the fall 2012 event, a drop organizers attributed to it being a rainy day.

The state’s collection success may be due to Maine having one of the oldest populations in the country, or aggressive prescribers.

However, Michael Wardrop, DEA agent in charge for Maine, believes it is because the issues has gotten a lot of attention here and Mainers are more concerned about keeping unwanted medicine out of the environment and out of the hands of children and burglars.

“Everyone has stepped up to the challenge and are scouring their cabinets and bedside tables,” he said. Also, some 60 to 65 police stations in the state now monitor collection boxes every day.

Wardrop understands his agency’s concern about diversion but thinks the data collected is important and hopes a method is approved to do it safely.

“That’s the type of information that can somewhat drive policy and the complex issues with respect to prescribing practices,” he said.

One threat to the collection program is that the federal DEA will cut funding for it. State officials worry the program would be cost-prohibitive for the state to take on itself but there are efforts underway to cut those costs.

All the medications collected now are taken to a specially licensed incinerator in Haverhill, Mass.; but the Department of Environmental Protection is working to allow them to be burned at the state’s three waste incinerators, which would be much less expensive.

Key to that effort is determining that air emissions from incinerating the medications poses no health risk. Ecomaine is scheduled to burn some of the material on Monday in a controlled way to gauge the effect, officials said.

The variety of medications — and other things — being turned in is remarkable, said Cumberland County Sheriff’s Deputy Joe Schnupp.

The sheriff’s office maintains a drop box at the county jail. On Thursday, Schnupp sifted through a week’s worth of collections, uncovering a blood pressure gauge and a blood sugar test kit as well as a multitude of medicines. The drugs ran the gamut from bottles of Tylenol to more than 100 doses of Diazepam, often sold as Valium. Some of the medicines were 15 years old.

He was cautious in handling the assortment. Hypodermic needles sometimes show up even though they are not allowed, he said.

More than 100 UNE pharmacy students have volunteered to catalog the wide variety of drugs that will be collected on Saturday at collection points in Belfast, Saco, Scarborough and the UNE College of Pharmacy. They must have their tabulations complete by 2 p.m., when police haul the medicine away for disposal.

Stewart said the collection effort has produced some eye-catching examples. One was a moving box full of unopened prescription lotion.

In another case, two people each brought in a load of medication that combined represented $10,000 worth of medication at the wholesale price.

“That’s the type of thing that is a real eye-opener,” she said.