Olanzapine pharmacokinetics in pediatric and adolescent inpatients with childhood-onset schizophrenia.

Well-designed studies investigating how pediatric or adolescent patients with mental disorders respond to and metabolize the newer antipsychotic drugs are practically nonexistent. Without such data, clinicians have difficulty designing appropriate dosage regimens for patients in these age groups. The results from a study of olanzapine pharmacokinetics in children and adolescents are described. Eight inpatients (ages 10-18 years) with treatment-resistant childhood-onset schizophrenia received olanzapine (2.5-20 mg/day) over 8 weeks. Blood samples, collected during dose titration and at a steady state provided pharmacokinetic data. The final evaluation (week 8) included extensive sampling for 36 hours after a 20-mg dose. Olanzapine concentrations in these eight pediatric patients were of the same magnitude as those for nonsmoking adult patients with schizophrenia but may be as much as twice the typical olanzapine concentrations in patients with schizophrenia who smoke. Olanzapine pharmacokinetic evaluation gave an apparent mean oral clearance of 9.6 +/- 2.4 L/hr and a mean elimination half-life of 37.2 +/- 5.1 hours in these young patients. The determination of the initial olanzapine dose for adolescent patients should take into consideration factors such as the patient's size. In general, however, the usual dose recommendation of 5 to 10 mg once daily with a target dose of 10 mg/day is likely a good clinical guideline for most adolescent patients on the basis of our pharmacokinetics results.

Penetration of tacrine into cerebrospinal fluid in patients with Alzheimer's disease.

Tacrine is widely used for the treatment of Alzheimer's disease, but data are limited regarding cerebrospinal fluid (CSF) concentrations at steady state. To evaluate CSF penetration, seven patients with Alzheimer's disease who were receiving tacrine at doses of 40 to 140 mg/day as a part of a double-blind trial were studied. After 6 weeks of tacrine therapy, concomitant plasma and CSF samples were collected 30 minutes after the morning dose of tacrine. Although this time point is before the peak oral absorption in most patients, the critical issue for this study is that the plasma and CSF samples were collected concomitantly so that a percentage of tacrine penetration could be derived. The morning dose of tacrine ranged from 10 to 40 mg, which was given in the fasting state. Mean (+/-SD) plasma levels of tacrine were 8.01+/-7.07 ng/mL, whereas mean (+/-SD) CSF levels of tacrine were 5.21+/-6.00 ng/mL. The mean (+/-SD) ratio of CSF to plasma tacrine concentration was 0.50+/-0.45, with wide interindividual variability. No relationship between dose and percentage of penetration was observed. Plasma concentrations ranged from 0.99 to 22.6 ng/mL and were unrelated to dose, suggesting erratic oral absorption and/or rapid metabolism. CSF concentrations ranged from not detectable to 15.92 ng/mL. The authors support that penetration of tacrine into CSF is highly variable in patients with Alzheimer's disease and that disparity in tacrine concentrations at the site of action may be one reason for conflicting results from studies of the efficacy of tacrine in Alzheimer's disease.

Pimozide-induced depression in men who stutter.

BACKGROUND: Neuroleptic-related dysphoric reactions are well recognized in the context of psychiatric disorders, especially in association with extrapyramidal side effects. Very few controlled data exist regarding the effects of neuroleptics on the mood of psychiatrically "normal" subjects. In this study, the depressogenic effect of the neuroleptic drug pimozide was assessed in men without psychiatric disorders. METHOD: Eight men with developmental stuttering but no past or present psychiatric illness participated in a double-blind, placebo-controlled study assessing the effect of 6 weeks of pimozide treatment on speech fluency and mood. RESULTS: Four of the seven subjects who were compliant with the treatment developed marked depressive symptoms. No clear association was found between these reactions and pimozide dose, blood level, or degree of neurologic side effects. Symptoms abated soon after drug discontinuation. CONCLUSION: Pimozide induced significant depressive symptoms in this group of psychiatrically normal men who stutter. Neuroleptic drugs may have a causal effect in the induction of depression in psychiatrically normal subjects, ostensibly independent of dose or severity of neurologic side effects.

Mixture risk assessment: a case study of Monsanto experiences.

Monsanto employs several pragmatic approaches for evaluating the toxicity of mixtures. These approaches are similar to those recommended by many national and international agencies. When conducting hazard and risk assessments, priority is always given to using data collected directly on the mixture of concern. To provide an example of the first tier of evaluation, actual data on acute respiratory irritation studies on mixtures were evaluated to determine whether the principle of additivity was applicable to the mixture evaluated. If actual data on the mixture are unavailable, extrapolation across similar mixtures is considered. Because many formulations are quite similar in composition, the toxicity data from one mixture can be extended to a closely related mixture in a scientifically justifiable manner. An example of a family of products where such extrapolations have been made is presented to exemplify this second approach. Lastly, if data on similar mixtures are unavailable, data on component fractions are used to predict the toxicity of the mixture. In this third approach, process knowledge and scientific judgement are used to determine how the known toxicological properties of the individual fractions affect toxicity of the mixture. Three examples of plant effluents where toxicological data on fractions were used to predict the toxicity of the mixture are discussed. The results of the analysis are used to discuss the predictive value of each of the above mentioned toxicological approaches for evaluating chemical mixtures.

Plasma clozapine and haloperidol concentrations in adolescents with childhood-onset schizophrenia: association with response.

BACKGROUND: Plasma clozapine and haloperidol concentrations were studied in adolescents being treated for childhood-onset schizophrenia. METHOD: Eleven patients (9 boys, 2 girls; mean age = 14.1 +/- 2.1 years) received a 6-week blinded or open trial of clozapine. Five patients also received 6 weeks of blinded or open haloperidol. Doses were increased on an individual basis to a mean 6-week dose of 5.99 +/- 2.6 mg/kg/day for clozapine and 0.24 +/- 0.20 mg/kg/day for haloperidol. The Brief Psychiatric Rating Scale and Bunney Hamburg Rating Scale were completed weekly for each subject. Weekly blood samples were obtained during therapy and assayed by high performance liquid chromatography. RESULTS: The mean clozapine level at Week 6 was 378.3 ng/mL and ranged from 77.5 to 1050 ng/mL. The mean Week 6 haloperidol level was 23.0 ng/mL (range, 6.2-44.3 ng/mL). The clozapine desmethyl and N-oxide metabolites achieved mean concentrations of 77% and 18%, respectively, of those of the parent compound. The mean ratio of haloperidol/reduced haloperidol was 4.48 (range, 0.76-8.76). Clozapine concentrations versus clinical benefit exhibited a consistent linear relationship among patients (correlation range, 0.26-0.96). Conversely, poor and inconsistent correlations between haloperidol concentrations and clinical effects were observed. No relationships were noted between clozapine or haloperidol dose and clinical effects. CONCLUSION: Adolescents with schizophrenia produce a greater amount of desmethylclozapine than previously seen in adults. Plasma clozapine concentrations appear to be related in a linear fashion to clinical improvement.

Attention-deficit hyperactivity disorder.

The epidemiology, etiology, pathogenesis, clinical presentation, diagnostic criteria, and clinical course of attention-deficit hyperactivity disorder (ADHD) are described and the role of pharmacotherapy in the management of this disorder is discussed. ADHD is a behavioral disorder of unknown etiology characterized by inattention, impulsiveness, and hyperactivity. The behavior, which may be manifest at home, at school, or in social situations, is generally worse in settings requiring sustained attention; as a result, academic underachievement is frequently an associated problem. Although the onset usually occurs before the age of four years, ADHD is most commonly diagnosed when the child enters school. It is up to six times more common in boys than in girls. Nearly one third of all children with ADHD continue to show symptoms of the disorder in adulthood. While many questions about the pathophysiology of ADHD remain unanswered and a cure has not yet been found, pharmacotherapy can effectively control the symptoms of the disorder in most patients. Three psychostimulant medications--dextroamphetamine sulfate, methylphenidate hydrochloride, and pemoline--are considered the drugs of first choice for management of the behavioral manifestations of ADHD. Dextroamphetamine and methylphenidate are equally effective in improving the symptoms of ADHD. Pemoline, a newer agent, may be tried in patients who cannot tolerate or do not respond to these two first-line agents. Common adverse effects associated with stimulant medications include anorexia, insomnia, stomach pain, and weight loss; these are generally transient and decrease with time. Imipramine hydrochloride and desipramine hydrochloride are less effective and may produce more serious adverse effects than the psychostimulants and are therefore considered second-line agents for the treatment of ADHD. Dextroamphetamine sulfate, methylphenidate hydrochloride, and pemoline have been shown to effectively control the behavioral symptoms of ADHD. For maximum impact, pharmacotherapy should be accompanied by behavioral, educational, and psychosocial intervention.