Stimulants - Psychopharmacology

Stimulants

Stimulant drugs, specifically amphetamines, were firstused to treat psychiatric disorders in the 1930s for their pronounced effects of CNS stimulation. In the past, they were used to treat depression and obesity, but those uses are uncommon in current practice. Dextroamphetamine(Dexedrine) has been widely abused to produce a high or to remain awake for long periods. Today, the primary use of stimulants is for ADHD in children and adolescents, residual attention deficit disorder in adults, and narcolepsy (attacks of unwanted but irresistible daytime sleepiness that disrupt the person’s life).

The primary stimulant drugs used to treat ADHD are methylphenidate (Ritalin), amphetamine (Adderall), and dextroamphetamine (Dexedrine). Pemoline (Cylert) is infrequently used for ADHD because of the potential for liver problems. Of these drugs, methylphenidate accounts for 90% of the stimulant medication given to children for ADHD (Stahl, 2006). About 10% to 30% of clients with ADHD who do not respond adequately to the stimulant medications have been treated with antidepressants. In 2003, atomoxetine (Strattera), a selective norepinephrine reuptake inhibitor, was approved for the treatment of ADHD, becoming the first nonstimulant medication spe-cifically designed and tested for ADHD.

Mechanism of Action

Amphetamines and methylphenidate are often termed indirectly acting amines because they act by causing release of the neurotransmitters (norepinephrine, dopamine, and serotonin) from presynaptic nerve terminals as opposed to having direct agonist effects on the postsynaptic receptors. They also block the reuptake of these neurotransmitters. Methylphenidate produces milder CNS stimulation than amphetamines; pemoline primarily affects dopamine and therefore has less effect on the sympathetic nervous system. It was originally thought that the use of methylphenidate and pemoline to treat ADHD in children produced thereverse effect of most stimulants—a calming or slowing of activity in the brain. However, this is not the case; the inhibitory centers in the brain are stimulated, so the child has greater abilities to filter out distractions and manage his or her own behavior. Atomoxetine helps to block the reuptake of norepinephrine into neurons, thereby leaving more of the neurotransmitter in the synapse to help con-vey electrical impulses in the brain.

Dosage

For the treatment of narcolepsy in adults, both dextroam-phetamine and methylphenidate are given in divided doses totaling 20 to 200 mg/day. The higher dosages may be needed because adults with narcolepsy develop tolerance to the stimulants and so require more medication to sustain improvement. Stimulant medications are also available in sustained-release preparations so that once-a-day dosing is possible. Tolerance is not seen in persons with ADHD.

The dosages used to treat ADHD in children vary widely depending on the physician; the age, weight, and behavior of the child; and the tolerance of the family for the child’s behavior. Table 2.7 lists the usual dosage ranges for these stimulants. Arrangements must be made for the school nurse or another authorized adult to administer the stimu-lants to the child at school. Sustained-released prepara-tions eliminate the need for additional dosing at school.

Side Effects

The most common side effects of stimulants are anorexia, weight loss, nausea, and irritability. The client should avoid caffeine, sugar, and chocolate, which may worsen these symptoms. Less common side effects include dizziness, dry mouth, blurred vision, and palpitations. The most common long-term problem with stimulants is the growth and weight suppression that occurs in some children. This can usually be prevented by taking “drug holidays” on weekends and holidays or during summer vacation, which helps to restore normal eating and growth patterns. Atomoxetine can cause decreased appetite, nausea, vomiting, fatigue, or upset stomach.

Client Teaching

The potential for abuse exists with stimulants, but this is seldom a problem in children. Taking doses of stimulants after meals may minimize anorexia and nausea. Caffeine-free beverages are suggested; clients should avoid chocolate and excessive sugar. Most important is to keep the medication out of the child’s reach because as little as a 10-day supply can be fatal.