乌鸦传媒

WASHINGTON -- A large proportion of patients prescribed a stimulant for ADHD aren't compliant with their medications -- and they may be taking other illicit substances instead, researchers reported here.

About a third of some 4,000 patients who gave urine samples turned up negative for their prescribed stimulants, , of Ingenuity Health -- a service of Ameritox, a medication monitoring company -- and colleagues reported at the here.

In samples where the prescribed stimulant wasn't detected, THC was present more than 20% of the time, and some combination of a nonprescribed opioid, nonprescribed benzodiazepine, THC and/or cocaine was found more than 38% of the time, they reported.

"There is actually a level of nonadherence we are aware of with ADHD medications, particularly stimulants -- methylphenidate and Adderall, primarily," Ko told 乌鸦传媒. While literature reports of medication nonadherence vary, "this really confirms the high rates that many clinicians suspect in clinical practice," she said.

Ko and colleagues analyzed urine samples from patients prescribed an ADHD medication, conducted between July 1, 2014, and June 30, 2015. The mean age of patients was 28; half were male. Patients were prescribed an amphetamine (78.1%), methylphenidate (21.1%), or both (0.8%).

Samples were analyzed for the presence of the following ADHD medications: dextroamphetamine sulfate (Dexedrine, Dextrostat, Zenzedi), mixed amphetamine salts (Adderall), lisdexamfetamine dimesylate (Vyvanse), methylphenidate hydrochloride (Concerta, Metadate, Methylin, Quillivant, Ritalin), methylphenidate transdermal (Daytrana), and dexmethylphenidate hydrochloride (Focalin).

Researchers also tested the samples for marijuana metabolite (tetrahydrocannabinol), cocaine metabolite (benzoylecgonine), and nonprescribed medications. They also used liquid chromatography/tandem mass spectrometry to confirm positive screening results.

Overall, 1,348 patient samples (32.9%) tested negative for the presence of the prescribed ADHD medication, and 2,746 samples (67.1%) tested positive for the prescribed ADHD drug.

Patients prescribed a methylphenidate ADHD medication were significantly less likely to have a negative test result than those prescribed an amphetamine ADHD medication (27.8% versus 33.8%; adjusted OR 0.76, 95% CI 0.63-0.91).

Patients who tested negative for their prescribed ADHD drug were significantly more likely than those who tested positive to have the following substances detected in the urine sample:

• A nonprescribed opioid (14.3% versus 9.7%; adjusted OR 1.41, 95% CI 1.14-1.75)
• A nonprescribed benzodiazepine (8.9% versus 6.3%; aOR 1.37, 95% CI 1.06-1.76)
• THC (20.7% versus 11.9%; aOR 1.64, 95% CI 1.33-2.03)
• Cocaine (1.7% versus 0.9%; aOR 1.69, 95% CI 0.92-3.10)
• Some combination of these drugs (38.7% versus 24.8%; aOR 1.71, 95% CI 1.44-2.04)

Nonadherence to ADHD medications was seen in a similar proportion of men and women (33.2% and 32.7%).

Patients ages 20 to 29 had the highest rate of negative test results (41.6%), followed by those ages 30 to 39 (35.1%) and 10 to 19 (32%). Patients age 60 and up had the lowest rate of negative test results (24.4%).

Nonadherence among younger patients may be attributed to the way medication is managed by parents, "or they just inherently, being ADHD patients, are unable to stick with the medication prescribed," Ko said.

Ko concluded that early detection of nonadherence, such as through urine monitoring, "is helpful across all patient groups, [both] for initial testing and for an ongoing basis to be able to monitor the patient's outcome [and ensure it] is optimized."

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