Finding the Most Effective Dose

Some medications are prescribed best according to the patient's age, weight, or severity of symptoms. But stimulant medications do not reliably follow such guidelines. Nora Volkow and James Swanson (2003) described individual differences that affect one's response to stimulant medications. Mark Rapport and Colin Denney (2000) demonstrated that body mass fails to predict optimal dose for ADHD patients. Some very young and small children need quite large and frequent doses of stimulant to get a positive effect; whereas other children, adolescents, and adults may benefit from very small doses of stimulant and may have adverse effects to larger doses. In short, more medication is not always better. And since it is not possible to predict the optimal dose from age, weight, or symptom severity, the usual approach is to begin with a very small dose of one or another of the stimulant medications and then increase the dose gradually, allowing about three to seven days on a dose before trying a larger one.

For decades, stimulant medications were available only in preparations effective for just four to five hours; for some whose bodies metabolized these agents more quickly, the effectiveness was much shorter, sometimes just two to two-and-a-half hours. This meant that schoolchildren were required to go to their teacher or a school nurse once or twice during the day to receive additional doses, and that adults on this medication had to remember to take three to four doses each day during their employment and daily routines. Given that persons with ADD syndrome are often chronically forgetful—and that classmates, teachers, or coworkers who did not understand or respect the reasons for such medications often had negative reactions to those who took them—many with ADD used these shorter-acting stimulants inconsistently, if at all.

Many improved, longer-acting formulations of stimulant medications are now produced. In countries where they are available, these extended-release preparations have revolutionized stimulant medication treatments for ADHD. They make it possible for children to avoid taking medication at school, and they reduce the number of times each day that adults must remember to take their tablets.

The American Academy of Child and Adolescent Psychiatry (AACAP) has published approved guidelines for use of stimulant medications in the treatment of children, adolescents, and adults (2002). For immediate release (short-acting) methylphenidate (MPH; sold as brands Ritalin or Methylin, or as generic methylphenidate), its recommended starting dose is 5 mg administered twice daily, increasing as needed by 5 mg weekly up to a usual maximum of 20 mg per dose; a third daily dose may eventually be added at the clinician's discretion. For preschoolers the starting dose is usually lower. Laurence Greenhill and colleagues (2004) reported that initial doses of 1.25 mg of MPH with gradual increments of 1.25 mg as needed, up to 7.5 mg three times daily, worked well for 85 percent of three-to five-year-olds in a multisite study sponsored by the National Institute of Mental Health.

For all ages, each weekly increase is to be made only after monitoring the effectiveness of the drug, the patient's weight and vital signs, and any side effects. Increases are made only when the current dose is not producing an adequate response and is not causing significant adverse effects. If a given dose continues to produce significant side effects, the dose is to be reduced or the medication stopped with the option of trying another compound. Standard dosing of short-acting MPH is three times daily, given at times adjusted to fit the individual's schedule and activities. Some individuals may require more frequent dosing, whereas others may respond better to taking the medicine only twice each day.

An alternative form of short-acting methylphenidate is Focalin. This formulation is produced by removing from methylphenidate one of its two components that reportedly is more likely to cause adverse effects.

The resulting dexmethylphenidate is a more potent compound available in 2.5, 5, and 10 mg doses usually started at about half of the usually administered dose of conventional methylphenidate; increases are also made at half of the usual increments for regular MPH. The medication is effective for about five to six hours. Some patients find it easier to tolerate this formulation than conventional MPH.

For short-acting dextroamphetamine (DEX; sold as Dexedrine or Dextrostat) or mixed amphetamine salts (AMP; available as Adderall or generic mixed amphetamine salts), AACAP-recommended doses are smaller than those for MPH. This is because DEX and AMP compounds tend to pack a bit more "punch" per milligram. The recommended starting dose of these agents is 2.5 mg for children and 5 mg for older adolescents or adults given once or twice daily, with increases of 2.5 mg every week until a good response is obtained. Once an effective dose has been identified, it is usually administered two to three times daily, depending on the patient's individual needs.

Although a single dose of fast-acting MPH, DEX, or AMP is effective for about four hours, some individuals get a much longer or much shorter response. This is one reason that it is so important for stimulant medication to be carefully monitored and adjusted to each individual's needs.

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