CHAPTER 29 Child Psychiatry Child Pharmacology I. General Concepts A. Pharmacokinetics: different in children 1. Drug distribution a. Less fatty tissue (less drug storage in fat) b. Protein binding may be unpredictable. c. Weight changes more rapidly, and changes are a greater percentage of total weight. 2. Elimination is generally faster than in adults. a. Higher glomerular filtration rate b. Larger hepatic capacity B. Pharmacodynamics 1. Central nervous system (CNS) is still developing; effects of medications may change with CNS maturation. 2. Surprising or paradoxic side effects may occur. 3. Therapeutic drug levels may not apply. C. Diagnosis: may be more difficult in children (e.g., attention deficit hyperactivity disorder [ADHD] or bipolar? schizophrenia or autism?) 1. Sometimes the diagnosis is established only after a response to pharmacotherapy. 2. Symptom-directed treatment is common. 3. Many childhood disorders have no specific treatment (autism, retardation, etc.). D. Most psychotropics: not approved by the U.S. Food and Drug Administration (FDA) for use in children E. Electroconvulsive therapy and psychosurgery: generally not indicated F. Children are minors: the child’s parents or guardians are the ultimate decision makers; treatment of any kind requires their informed consent. II. Psychotropics Used Mostly in Children A. Medications for ADHD 1. Amphetamines a. Effects i. Increased release of catecholamines (norepinephrine [NE] and dopamine [DA]) (A) Increased attention and concentration (B) Increased motivation ii. Reduced hyperactivity, aggression iii. Similar behavioral responses occur in children without ADHD (i.e., improvement with amphetamine is not diagnostic of ADHD). b. Specific drugs i. Methylphenidate (Ritalin®, Metadate®, Concerta®): the most frequently used ii. Dextroamphetamine (Dexedrine®) iii. Mixed amphetamine salt (Adderall®) c. Adverse effects i. Can worsen tics (which are often comorbid) ii. Insomnia, anorexia, nervousness iii. Potentially habit forming iv. If stimulants suppress growth, the effect is minimal, and growth catches up eventually. v. Toxicity: hallucinations and seizures 2. Pemoline (Cylert®) a. Nonamphetamine stimulant b. Longer-acting than most amphetamines c. Withdrawn from U.S. markets in 2005 due to liver toxicity 3. Antidepressants: black-box warning: antidepressants increase the risk of suicidal thinking and behavior in children, adolescents, and young adults (18–24 years of age) with major depressive disorder and other psychiatric disorders. a. Tricyclics i. Likely work through NE reuptake inhibition ii. Therapeutic effects may be evident within days (unlike in depression). iii. Desipramine: effective but associated with sudden cardiac death b. Bupropion (Wellbutrin®) i. Increased NE and DA transmission ii. Decreases seizure threshold 4. Atomoxetine (Strattera®) a. Nonstimulant; selective NE reuptake inhibitor b. May cause drowsiness 5. Presynaptic α2-noradrenergic agonists (not FDA approved) a. Clonidine (Catapres®), also available as a patch b. Guanfacine (Tenex®) may be more frontal lobe specific than clonidine c. Can cause hypotension, dysrhythmias, sedation d. Rebound hypertension can occur if discontinued suddenly B. NB: Medications for Tourette’s disorder 1. Antipsychotics are the most effective treatments—probably work through DA blockade a. NB: Pimozide (Orap®): not frequently used but is a test answer b. NB: Haloperidol (Haldol®) c. Risperidone (Risperdal®) d. Risks i. Extrapyramidal side effects, tardive dyskinesia ii. QT prolongation—monitor with serial electrocardiographies. 2. Clonidine (less effective, but no risk of tardive dyskinesia) C. Medications for enuresis 1. Tricyclics a. Effective in 60% of patients b. Low doses, given approximately 1 hour before bedtime c. Clomipramine (Anafranil®): most commonly used 2. Desmopressin a. Analogue of antidiuretic hormone b. Effective in approximately 50% of cases c. Dosed intranasally d. Can cause water retention D. Medications for self-injury (in developmental disorders) 1. Antimanic agents, such as lithium and anticonvulsants 2. Antipsychotics—risperidone and aripiprazole in autism spectrum disorders 3. Nonspecific sedatives, such as benzodiazepines and antihistamines 4. β-Blockers sometimes have a calming effect. 5. Opioid antagonists naloxone (Narcan®) and naltrexone (Revia®) Childhood Psychiatric Illnesses Childhood psychiatric illnesses differ from adult illnesses in two ways. First, children may present with unusual symptoms of adult illnesses. Second, as in neurology, children have their own unique diagnoses that rarely present in adulthood. This chapter is not intended to be a comprehensive review of these illnesses but to present those that are likely to come to the attention of a neurologist (in real life or on an examination). III. Mental Retardation (Now Called Intellectual Disability; Renamed by Federal Statue 111-256, Rosa’s Law) A. Categorization 1. Mild a. Intelligence quotient (IQ): 50 to 70 b. 6th-grade educable c. May be able to hold simple job 2. Moderate a. IQ: 35 to 50 b. 2nd-grade educable c. May be able to function in sheltered workplace 3. Severe a. IQ: 20 to 35 b. May be able to talk or otherwise communicate c. Unlikely to benefit from vocational training d. May be able to protect self and perform simple hygiene 4. Profound a. IQ: less than 20 b. May develop rudimentary speech in adulthood c. Will require nursing care B. Causes 1. NB: Down syndrome a. Trisomy 21: most common cause b. Incidence: 1/700 live births (1 in 100 if mother >32 years old [y/o]) c. Signs i. Physical examination: hypotonia, oblique palpebral fissures, extra neck skin, protruding tongue, single palmar crease (simian crease) ii. Mental development seems normal until 6 months; IQ decreases after age 1 year. iii. As children, they are usually quite pleasant and placid. iv. Various behavioral problems can develop in adolescence. d. Prognosis/complications i. Frequent childhood infections (depressed immune system) ii. Outcome can range from holding jobs to lifelong institutionalization (10%). iii. NB: Early-age Alzheimer’s symptoms and neuropathology (age 30–40 years) iv. Atlantoaxial instability may cause myelopathy. 2. NB: Fragile X syndrome a. Caused by trinucleotide repeat at chromosomal locus Xq27.3 b. Incidence: 1/1,000 males, 1/2,000 females c. Diagnosis i. Long head, large ears, hyperflexible joints, macroorchidism, short stature ii. Mild to severe intellectual disability iii. These patients are often gregarious and pleasant. iv. Females are usually less severely affected. v. High frequency of ADHD and pervasive developmental disorders
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