INVESTIGATING GENERICS: They Say Their ADHD Meds Aren’t Working. They’re Not Imagining It

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The first time Marilynn Monroe took Adderall (a combination of amphetamine and dextroamphetamine) for her ADHD, she says she cried tears of joy. She was 15 years old.

“The symptoms that were holding me back from living a semi-normal life [started with], obviously, the inability to focus,” she says. “But it was so much more than that. It was anxiety and depression that were caused by my lack of ability to focus and be organized.”

Now 32 and living in Virginia, Monroe says her Adderall just isn’t working like it used to.

For years, people living with ADHD have insisted that not all medications for the condition are created equal, even if generic and branded drugs are considered to be equivalent to each other by the Food and Drug Administration (FDA). This whisper of complaints has grown into a chorus as ADHD medication shortages have gripped the country since October 2022 — forcing patients to switch manufacturers month to month, depending on what’s been available

In the last three years, Monroe says she has taken 20 milligrams of generic instant-release amphetamine made by the pharmaceutical companies Teva and Sandoz, as well as brand-name Adderall, which is also made by Teva. At first, she had positive experiences with Teva’s generic version of the medication, but more recently, she says, not only did it stop controlling her symptoms most of the time, but it started causing constipation, angry outbursts, and other side effects. She had similarly unreliable results with Sandoz’s version of amphetamine, which also caused her debilitating acid reflux.

Even when her manufacturer hasn’t changed, Monroe says side effects and symptom control vary from refill to refill. “It’s batch to batch,” she says. When she spoke to MedShadow in April of 2025, she was taking Sandoz’s version of the drug, which seemed to be helping to some degree.

“Every single month I pick up my prescription, it’s basically like I’m playing Russian roulette,” she says.

Jamie Alan, RPH, PharmD, an associate professor of pharmacology and toxicology at Michigan State University, says ongoing shortages have forced people to switch medications frequently. “They’ve been hopping around,” she says. “There’s been a lot of patient complaints, and physicians have been noticing that these [drugs] are not working the same, from brand to brand and even from batch to batch.”

Issues with ADHD drug variability aren’t just anecdotal. In February 2023, a team of researchers from Stanford University, Massachusetts General Hospital, and Valisure (an independent laboratory) acquired samples of methylphenidate (Ritalin) from 18 different manufacturers, all sourced from a single wholesaler. When they chemically analyzed the medications, they found notable differences in how the drugs dissolved, suggesting that medications intended to be identical were, in practice, delivering varying doses, especially among extended-release formulations.

Some of the tested medications also contained N-nitroso-methylamine, a potentially carcinogenic contaminant similar to N-nitrosodimethylamine (NDMA), a probable carcinogen found in other medications.

What Is ADHD Medication and How Does It Work?

The two broadest categories of ADHD medications are stimulants, such as Adderall, and non-stimulants, such as Strattera (atomoxetine). Stimulant medications work by increasing the levels of dopamine, a chemical that influences motivation and learning in your brain. Non-stimulants, which are considered to be less effective than stimulants but may be helpful for patients who experience side effects with stimulants, typically target another chemical, norepinephrine.

Stimulants can be methylphenidate (such as Ritalin) or amphetamines (such as Adderall). They also come in a variety of formulations that release the medication into the body at different rates, including instant-release, extended-release, long-acting and sustained-release versions.

As of 2023, the Centers for Disease Control and Prevention (CDC) estimates that 15.5 million adults in the U.S. — most between the ages of 25 and 49 — had been diagnosed with ADHD, with one-third of them prescribed a stimulant. Seven out of 10 of those individuals said they’d had a hard time getting their medication because of limited availability. In 2022, the CDC also reported that an estimated 7 million children in the U.S. had been diagnosed with ADHD, with just over half (53.6%) receiving a prescription for medication.

Mary Bryerton, who lives in Chicago, was initially prescribed a nonstimulant medication when she was diagnosed with ADHD, but she says it made no difference in her symptoms. Next, her doctor prescribed a stimulant, Vyvanse (lisdexamfetamine). It worked immediately.

“It was like a light switch for me,” she says, noting that she was finally able to finish tasks and organize her activities.

Within two years, however, the medication (which was initially approved by the FDA in 2007 but did not have a generic version approved until 2023) became too expensive for her, and she was switched to Adderall, which had generic versions.

What Are Generic Drugs?

The overwhelming majority — nine out of 10 — of prescriptions of all kinds filled in the U.S. are for generic drugs.

Essentially, generic drugs are less expensive versions of existing brand-name drugs. Because a pharmaceutical company must invest years of research and millions of dollars into developing a drug, that drug’s patent is exclusive for several years after its approval. But when that patent expires, other companies can start to make and sell their own versions of the same drug for a lower price, thanks to the Hatch-Waxman Amendments of 1984.

Instead of conducting full clinical trials, companies wishing to market generic drugs have to submit data to the FDA showing that their drug is interchangeable with the brand-name drug, or “bioequivalent.” To do this, the manufacturing company has to submit its manufacturing protocol and data on a small number of human participants showing that the drug contains the same active ingredient in similar proportions and is absorbed into the body at a comparable rate to the brand-name drug.

The generic must also use the same delivery method as the branded drug (such as an immediate release tablet or an extended release tablet), and while any inactive ingredients do not need to be the same as the branded drug, they must be considered safe.

‘Striking Differences’: Study Highlights Generic Drug Variability

When the researchers from Stanford and Mass General teamed up with Valisure for their study, they gathered samples of methylphenidate: 18 immediate-release (IR) tablets, 24 extended-release tablets (ERT), and 11 extended-release capsules (ERC) sold in February 2023 from a single wholesaler. Then, they set about determining how similar the drugs were to the branded medications they were designed to replicate.

The scientists tested how quickly the pills dissolved — since variations from a brand-name drug can result in inconsistent dosing, reduced effectiveness, or unexpected side effects — and whether they contained NNMP, a member of a class of chemicals that commonly contaminates many types of drugs and may raise the risk of cancer at higher doses over time. It has been found above safe limits in many products, such as metformin and ranitidine, and has led to recalls.

Novartis manufactures the branded version of methylphenidate IR (Ritalin). All 18 IR methylphenidate drugs tested dissolved at rates comparable to Novartis’ Ritalin; however, versions produced by pharmaceutical companies Amneal, Camber, and SpecGX were found to contain NNMP levels above the recommended limits.

In contrast, 12 of the 24 extended-release tablets (ERTs) dissolved at rates significantly different from a branded version (Concerta) made by Janssen Pharmaceuticals. Products made by pharmaceutical manufacturers Kremers Urban Pharmaceuticals, SpecGX, and Trigen Pharma all showed inconsistent dissolution, as did the 36-milligram doses from Lannet and Mylan and the 27-milligram doses from Camber and Actavis.

ERTs made by Kremers were also contaminated with NNMP, but the level remained below the recommended limits.

Of the ERCs, those made by Sandoz dissolved at the same rate as Novartis’ Ritalin LA, but capsules made by Mayne and Granules dissolved at different rates. None contained NNMP above the recommended limits.

The research “showed some striking differences,” says Dr. Alan, who was not involved in the study.

Joshua Kolman, PharmD, a clinical pharmacist at Corewell Health in Michigan who was also not involved in the study, notes that the NNMP contamination findings are concerning, adding that it’s critical to have the FDA inspect drug manufacturers to ensure they’re using good manufacturing practices that prevent contamination.

Because the researchers tested the drugs at only one point in time, it’s unclear whether these results vary from batch to batch, or whether results from February 2023 apply to medications purchased today. Additionally, the researchers only analyzed methylphenidate; they did not study amphetamines or any other types of medications. However, Valisure has since partnered with the Department of Defense and is conducting similar tests on a variety of medications.

“The take-home for me is that this validates patient experiences,” says Dr. Alan. “and [it] does signify a larger problem” with the drug manufacturing process.

How Quality and Supply Issues Can Reduce Effectiveness of ADHD Meds

Stimulant prescriptions have been on the rise since 2012, increasing by 45.5% between 2012 and 2021, and soaring during the pandemic — all while manufacturing lagged.

This led to drug shortages throughout the country, which may have been further exacerbated by a Drug Enforcement Administration (DEA) crackdown on drugmakers. As of May 22, 2025, shortages of amphetamines and methylphenidate ER persist.

Several ADHD medications have also been recently recalled, further compounding the problem.

In 2023, a batch of methylphenidate made in a New Jersey lab for Sun Pharma was found to be contaminated with metal. In January 2025, Glenmark Pharmaceuticals recalled nearly 1.5 million bottles of generic non-stimulant atomoxetine because it contained a carcinogen. The medications had been manufactured in a lab in India and distributed in the U.S. by Glenmark Pharmaceuticals (New Jersey) and Northstar RX LLC (Memphis, Tennessee). Later in January, Massachusetts-based Azurity recalled a batch of its dextroamphetamine sulfate tablets (marketed under the name Arbor Pharmaceuticals LLC), because at least one bottle contained an antihistamine instead of the ADHD medication.

These shortages and recalls forced people to take a drug from whichever manufacturer was available when their refills were due. As individuals switched back and forth between brands, differences in efficacy became all the more noticeable.

“The Adderall isn’t adderall-ing this month,” Bryerton told MedShadow during an interview in March 2025. While she tries to get amphetamine made by Teva — which has offices and labs all over the world — when she can, Bryerton had to settle for a different manufacturer in March.

Since the manufacturer wasn’t listed on the new bottle, she has no way of knowing which brand she’s taking.

Healthcare providers say they’ve seen their patients respond to medications differently when they’ve had to switch manufacturers.

“Even though generics are supposed to be ‘bioequivalent’ to brand-name drugs, small differences in how they’re absorbed or how long they last in the body can affect how someone feels or functions,” says Savanna Howe, Psy.D., a clinical psychologist in Arizona. “So yes, a patient might feel great one month and then struggle with focus, mood, or side effects the next — simply because the refill came from a different generic producer.”

A Regulatory Clash Over Issues with Generic Concerta

The FDA has been aware of these concerns for years. In November 2014, the agency flagged two generic versions of Concerta — the extended-release form of methylphenidate hydrochloride — manufactured by Mallinckrodt, under its subsidiary SpecGX, and Kudco, now UCB Kremers Urban. Agency tests revealed that the generics dissolved more slowly in the body than the brand-name drug, raising questions about their therapeutic effectiveness.

Concerta’s delivery system, which gradually releases the medication into the body, is “very hard to replicate,” notes Dr. Kolman.

These testing results caused the FDA to revise the generics’ bioequivalence ratings in its Orange Book from AB to BX, a downgrade that signaled to prescribers and pharmacists that the products were no longer considered interchangeable with the original. Though the drugs remained on the market, the agency asked both manufacturers to either submit new data demonstrating equivalence to brand-name Concerta or voluntarily withdraw their products.

Instead, Mallinkrodt sued the FDA for unlawfully reclassifying the drug in the Orange Book, requesting that its AB rating be reinstated. A judge denied the motion.

(If the name “Mallinckrodt” sounds familiar, it might be because the company was asked to either pay claims of $41.1 million or the state of New York $58.5 million in 2022 for its role in perpetuating the opioid crisis.)

In October 2016, the FDA stepped in again and proposed that the two drugs be removed from the market. The FDA gave the companies the required 30 days notice to request a hearing. Both companies corresponded back and forth with the FDA for several years.

Though the comment period on the 2016 notices officially ended in December 2016, in February 2019, Alvogen, another generic drug manufacturer, submitted a comment on the notices for each company saying that the companies were still selling these drugs to many patients who likely believed they were getting a bioequivalent drug. It urged the FDA to officially remove the products from the market. Both drugs remain in the Orange Book with BX labels as of May 26, 2025.

The FDA did not respond to MedShadow’s request for comment.

What to Do if You Think Your Medication Isn’t Working

When you pick up your medications from the pharmacy, see if you can find the name of the manufacturer on the drug label, or ask your pharmacist to confirm it. It’s also important to make sure you check how your medication looks, says Dr. Alan. If they are a different color or shape, the manufacturer may have changed. That’s a clue to pay extra close attention to how you feel, and if you don’t feel right, make sure to tell your healthcare provider.

Dr. Kolman says one of the most important changes to pay attention to is how long your medication seems to be lasting. “How soon is the medication’s effectiveness ending? We would expect somewhere between eight to 10 hours, up to 12, with Concerta for the extended release products,” he says. “If we’re seeing the effect starting to decrease at like six to eight, we may want to consider switching to a different generic or changing the dose around to see if we could overcome that.”

When Monroe’s generic drugs stopped working, she asked her doctor for help. She prescribed her brand-name Adderall. However, insurance remained a struggle, and Monroe first had to pay hundreds of dollars out of pocket for the drug. Luckily, her insurance eventually reimbursed her.

Bryerton says her last year and a half of constantly switching manufacturers has been “a nightmare.” Still, given the shortages, she’s afraid to voice her concerns. She hasn’t mentioned the issues to her doctor or pharmacist because, she says, she’s worried that if she rocks the boat, she won’t get her medication at all.

Dr. Howe recommends keeping a symptom log and bringing it with you to talk to your healthcare provider. “Sometimes pharmacies can order a specific generic, or switch [you] to a brand-name version if the variability is too disruptive. It’s not all in your head,” she continues, “and you’re not alone in noticing it.”