Researchers Find Few Comparisons of Most ADHD Drugs

ADHD Medication

Parents seeking the best individual drug for their children with attention deficit hyperactivity disorder have little hard evidence to help make that choice.

There are few head-to-head clinical comparisons of many ADHD medications, despite the relatively large variety of drugs prescribed for ADHD and the prevalence of the condition among children and adults, according to a new review from the Oregon Evidence-based Practice Center at the Oregon Health and Science University.

The Oregon Evidence-based Practice Center makes available information regarding the comparative effectiveness and safety profiles of different drugs within pharmaceutical classes.

The majority of the head-to-head trials identified by the Oregon reviewers, led by Dr. Marian McDonagh, compared the widely prescribed ADHD medication Ritalin with other drugs. Most of these comparative trials were short in duration, included only a small number of patients and did not measure the long-term effects of the drugs.

As for safety, the researchers found, "Short-term, randomized controlled trials do not provide clear evidence that any one stimulant is any more tolerable than another or that nonstimulants are more tolerable than stimulants."

None of the trials compared how well the drugs performed in terms of improving academic performance, quality of life or social skills, the researchers found.

Stimulant medications such as Ritalin and amphetamines are most often prescribed for ADHD, but the Oregon study includes several types of ADHD medications that have never been examined before in a systematic review, including newer stimulants such as modafinil and non-stimulant drugs such as Strattera (atomoxetine), antihypertensive drugs such as guanfacine and older antipsychotic drugs such as clozapine.

The studies "do not answer the question of whether any one stimulant suppresses growth in height any more than any other," say the researchers, and do not show a consistent relationship between Ritalin and stunted height, a key concern of some parents with children taking the drugs.

Limited evidence suggests that the antihypertensive drugs clonidine and guanfacine reduce the severity of facial tics in children with ADHD, but the two drugs are not approved by the Food and Drug Administration for the treatment of ADHD, according to McDonagh and colleagues.

According to Dr. Heidi Feldman, a pediatrics researcher at the University of Pittsburgh, the American Academy of Pediatrics guidelines recommend a stimulant drug such as Ritalin as the first type of drug to try in ADHD treatment.

But "few studies pit one stimulant against another in a head to head comparison. Those studies show that there are no advantages to one stimulant over the others. So it is completely legitimate for a physician to choose any one of the stimulants as his or her first line, and learn to use that one well," Feldman says.

"Physicians are supposed to adjust the dose of this initial medication to obtain the most favorable benefits with the least side effects. It often takes two or three dose adjustments to determine which is the best dose for a given child. Only after such adjustments prove that the medication is either ineffective or causing adverse conditions should one try another medication," she adds.

The review included 146 studies, a combination of randomized controlled trials, the "gold standard" of clinical research, as well as observational studies. Observational studies, although less rigorous than randomized controlled trials, were included to ensure the largest possible amount of data on the medications' side effects, says Dr. John Santa, assistant director for health projects at the Center for Evidence-based Policy.

Significantly, only half of the studies in the review had any data on race or ethnicity, and only one-quarter of the studies on school-age children reported the type of ADHD treated. There are also very few studies comparing the effectiveness of different drugs in treating adults with ADHD, the researchers found.

A recent study by the prescription management company Medco Health Solutions concluded that prescriptions for ADHD medications for adults ages 20 to 44 doubled between 2000 and 2004.

Attention deficit hyperactivity disorder is usually characterized by consistent inattention, hyperactivity or impulsiveness. People with ADHD are usually diagnosed with one of three types of the disorder: inattentiveness type, hyperactivity type or mixed-symptom type. Mixed symptoms disorders are most commonly diagnosed. Boys are twice as likely as girls to be diagnosed with ADHD.

In a study released earlier this month, the Centers for Disease Control and Prevention reported that in 2003 nearly 8 percent of American children ages 4 to 17 had been diagnosed with ADHD. Over half of those children were taking medication for the condition.