One reason for regarding ADD as a distinct disorder with a biological origin is the immediate and striking relief from some of its symptoms provided by the stimulant drugs methylphenidate (Ritalin), dextroamphetamine (Dexedrine), and magnesium pemoline (Cylert). These drugs are helpful for about 75% of children and adults with ADD. They become less irritable and restless, and their attention and motor coordination improve; others begin to like them better, and they begin to think better of themselves. The drugs have no direct effect on learning disabilities, but may make special education and tutoring easier. There is little danger of drug abuse or addiction, because patients do not feel euphoria or develop tolerance or craving. They become dependent on stimulant drugs, it has been said, only in the same sense that a person with diabetes is dependent on insulin or a nearsighted person on eyeglasses. The main side effects - appetite loss, stomach aches, nervousness, and insomnia - usually subside within a week or can be eliminated by lowering the dose. A child's rate of growth may be slowed for a few years while he is taking a stimulant, but it returns to normal in adolescence. There is no evidence of long-term deleterious effects.

Methylphenidate and dextroamphetamine are short-acting drugs, but they are now available in time-release capsules that prolong the effects to eight or ten hours. Pemoline is longer-acting. The drug is started at a low dose that is gradually increased if necessary; parents can make adjustments according to the child's level of activity. If the symptoms do not improve after two weeks at the highest acceptable dose, drugs will probably never be useful. Some experts recommend that children take stimulants only during school hours and not on weekends or vacations. Most believe that drug treatment should be discontinued for several weeks once every six months or once a year to see whether it is still needed.

Several other kinds of drugs are also used in treating ADD, especially when the patient does not improve on stimulants or cannot tolerate their side effects. Beta-blockers such as propranolol (Inderal) or nadolol (Corgard) can be prescribed along with (or occasionally instead of) stimulants to reduce jitteriness. Tricyclic antidepressants, especially desipramine (Norpramin), are sometimes effective at doses lower than those used for depression; their most serious potential side effect is disturbance of heart rhythms. Another drug occasionally prescribed for ADD is clonidine, which is ordinarily used to lower blood pressure and suppress tics. Its most common troublesome side effect is drowsiness.

Most of these drugs alter the effects of one of the catecholamine neurotransmitters, norepinephrine or dopamine; either the transmitter's rate of release or reabsorption is changed, or the brain's sensitivity to it is affected. Neurons that produce these transmitters are located in the RAS and nucleus accumbens, among other regions. Although brain systems using catecholamines are clearly essential for the regulation of attention, the precise way they work is not yet understood. The effects of stimulant drugs were once described as "paradoxical" because they seemed to make children with ADD calmer rather than more active. The paradox, if it is one, is not confined to people with ADD, since low doses of stimulants have been found to improve concentration and reduce restlessness in most children.

Not a panacea

The long-term benefits of drug treatment are uncertain. It is difficult to predict which children will be helped and how long the drugs will be needed. Anxiety, depression, learning disabilities, and conduct disorders are not directly affected by the drugs. Although children may calm down, concentrate better, and behave less disruptively while taking a stimulant, there is no solid evidence that their schoolwork improves in the long run or that the adult outcome is affected. The original symptoms usually return in full force when a child stops taking the drug. Far from becoming addicted to stimulants, children and especially adolescents with ADD are often reluctant to take the drugs at all. They may be embarrassed about having to see a school nurse at noon to take a pill and humiliated by the implication that they cannot control their own behavior. Adolescents dislike the feeling of being different, defective, or dependent. In one study, 20% of hyperactive children who had agreed to take drugs for a year stopped by the fourth month, and nearly 50% by the tenth month. Another study found that only 22% of children given prescriptions for stimulants continued to take them for as long as two years.

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