FRIDAY, Jan. 6 (HealthDay News) -- If the current shortage of some drugs used to treat attention-deficit/hyperactivity disorder (ADHD) has left you searching for something else for your child to take, experts suggest you choose a substitute carefully because the effects of these medications can vary widely.

For example, "generics can sometimes be less bioavailable [how much of the drug is absorbed into the bloodstream], and that can make it harder to get an exact dose match between medications," explained Dr. Eric Hollander, director of the Autism and Obsessive-Compulsive Spectrum Program at Montefiore Medical Center in New York City.

"If the dose is too high, sometimes kids can get more withdrawn or weepy. If it's too low, they can't get adequate control of their symptoms during the day, and they can get a rebound later in the day. The new medicine may wear off faster. It's also not easy to switch from extended-release formulas to immediate-release," Hollander said.

The driving force behind the shortage is a U.S. Drug Enforcement Administration (DEA) policy that sets limits on the manufacturing of ADHD drugs, to limit the supply of these drugs to people who might use them illegally, according to a report by The New York Times. In some cases, drug companies manufacture both generic versions of ADHD drugs as well as the more expensive, branded versions, which can limit choices even further.

"This is the unfortunate result of well-intentioned policies combined with free market forces. It's a very substantial issue, and one that's affecting some families more than others," said Dr. Andrew Adesman, chief of developmental and behavioral pediatrics at the Steven and Alexandra Cohen Children's Medical Center of New York in New Hyde Park.

Whatever the reason behind the shortage, several drug companies that produce amphetamine products, including Adderall, have reported shortages to the U.S. Food and Drug Administration. And, companies producing various forms of methylphenidate are also seeing shortages.

Both Hollander and Adesman said they've had reports from parents that Adderall and its generic equivalent have been harder to get. They both suggest that parents call from pharmacy to pharmacy in their area to see which one might carry the needed medication.

If you can't find any pharmacy that has the medication you're looking for, let your child's doctor know. If the medication isn't available, they can first try another medication in the same class of medications. For example, Adderall is an amphetamine derivative. Vyvanse is another medication in that class. However, some insurance companies may balk at paying for medications that aren't on their preferred drug list, and you may have to pay a higher co-pay.

If there's a shortage of generic methylphenidate, the brand-name versions (Concerta, Focalin, Ritalin, Metadate and Daytrana) may be available.

There are also non-stimulant medications for ADHD, such as Intuniv, Kapvay and Strattera, that may be an option, Adesman said.

Dr. Michael Hobaugh has more experience than he'd like with having to switch children's ADHD medications. Most of his patients are on public insurance, which means he has to follow the state prescription drug formulary for these patients. And that formulary often changes several times a year.

"Sometimes, the switch is easy. It's very patient-dependent. Usually there is a similar product that's close enough, but some kids have trouble," said Hobaugh, who is the chief of medical staff at La Rabida Children's Hospital in Chicago.

"It can be a difficult trial-and-error process to figure out what works for some patients," he said. "Their lives aren't uniform from day to day. Is it a side effect of the medication, or does the child have a virus or stress, or maybe didn't get enough sleep? And trying to assess what the ideal medicine is for school readiness is difficult because there's so much you can't control. This introduces another factor you can't control."

There have been several ADHD drugs that have been difficult to get in the past year, Hobaugh noted, often because they're manufactured only by one company. That means if there's a production issue, there's no other manufacturer to fill in the gap.

"And, with generic drugs there may not be a whole lot of profit, so they're not a priority," he added.

Along with discussing the shortage with your child's doctor, Adesman suggested that parents can call or write the FDA, or a local government representative, and let them know that they're having trouble getting necessary medication.

"Patient advocacy is always important," he said. "It's the squeaky wheel that gets the grease."

More information

Learn more about medications used to treat attention-deficit/hyperactivity disorder from the U.S. National Institute of Mental Health.