Dale R. Grothe

Case study: Risperidone-induced hepatotoxicity in pediatric patients

The purpose of this case study is to document hepatic adverse effects associated with long-term risperidone use in pediatric populations. Charts of all patients admitted to the National Institute of Mental Health (NIMH) from December 1993 to April 1996 who had been treated with risperidone were screened for hepatotoxicity and weight gain. From the medical records of 13 psychotic children admitted to the NIMH and treated with risperidone, 2 children (both male) who presented with obesity, liver enzyme abnormalities, and confirmatory evidence of fatty liver were identified. In each case liver damage was reversed after discontinuation of risperidone and/or associated weight loss. The observations suggest that long-term risperidone therapy is possibly associated with hepatotoxicity in male pediatric patients. It is recommended that pediatric patients treated with risperidone have baseline liver function tests, careful monitoring of weight, and periodic monitoring of liver function tests during the maintenance phase of therapy.

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 patients 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.

Clozapine pharmacokinetics in children and adolescents with childhood-onset schizophrenia

Clozapine (CLZ) dose-related adverse effects may be more common in children than adults, perhaps reflecting developmental pharmacokinetic (PK) differences. However, no pediatric CLZ PK data are available. Accordingly, we studied CLZ and its metabolites, norclozapine (NOR), and clozapine-N-oxide (NOX) in six youth, ages 9–16 years, with childhood onset schizophrenia (COS). At the time of the PK study, mean CLZ dose was 200 mg (3.4 mg/kg). Serum was collected during week 6 on CLZ before and 0.5–8 h after a morning dose. Serum concentrations were assayed by liquid chromatography/UV-detection. Mean concentration, area-under-the-curve (AUC), and clearance were calculated. CLZ clearance averaged 1.7 L/kg-h. NOR concentrations (410) exceeded CLZ (289) and NOX (63 ng/ml) and AUC0–8h of NOR (3,356) > CLZ (2,359) > NOX (559 ng/ml-h) [53, 38, and 9% of total analytes, respectively]. In adults, NOR serum concentrations on average are 10–25% < CLZ, differing significantly from our sample. Dose normalized concentrations of CLZ (mg/kg-d) did not vary with age and were similar to reported adult values. Clinical improvement seen in 5/6 patients correlated with serum CLZ concentrations. In addition, clinical response and total number of side effects correlated with NOR concentrations. NOR (a neuropharmacologically active metabolite) and free CLZ may contribute to the effectiveness and adverse effects in youth.

Gabapentin does not alter single-dose lithium pharmacokinetics

Lithium (Li) and gabapentin are both exclusively eliminated by renal excretion. When used in combination, a competitive drug-drug interaction could possibly alter Li renal excretion with important clinical implications considering the rather narrow therapeutic index of Li. This study examined the single-dose pharmacokinetic profiles of Li in 13 patients receiving placebo and then steady-state gabapentin (mean daily dose: 3,646.15 mg). During both phases, a single 600-mg dose of Li was orally administered with serial Li levels obtained at time zero and at 0.25, 0.5, 1, 2, 3, 4, 8, 12, 24, 48, and 72 hours. The pharmacokinetic parameters assessed were the following: area under the concentration time curve (AUC) for Li, maximal concentration of Li (Li Cmax), and time to reach peak Li concentration (Li Tmax). For patients receiving gabapentin, the mean Li AUC at 72 hours was 9.91+/-3.54 mmol x hr/mL and did not differ significantly from the mean Li AUC of 10.19+/-2.89 mmol x hr/mL for patients receiving placebo. The mean Li Cmax was 0.69+/-0.13 mmol/L for gabapentin patients and did not differ from the mean Li Cmax of 0.72+/-0.15 mmol/L for placebo patients. The mean serum Li Tmax was 1.38+/-0.62 hours for gabapentin patients and did not differ significantly from the mean serum Li Tmax of 1.5+/-0.91 hours for placebo patients. These data indicate that gabapentin treatment at this high therapeutic dose does not cause clinically significant alterations in short-term Li pharmacokinetics in patients with normal renal function. These preliminary data warrant further controlled study in a larger, more heterogenous patient sample and a longer duration of assessment, but they do suggest that these two medications may be administered in combination for the management of bipolar disorder.

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

Tacrine is widely used for the treatment of Alzheimers disease, but data are limited regarding cerebrospinal fluid (CSF) concentrations at steady state. To evaluate CSF penetration, seven patients with Alzheimers 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 Alzheimers 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 Alzheimers disease.

Major Depression: Its Recognition and Treatment Part 2. Second-Generation and Newer Antidepressants

Abstract Newer agents, including the serotonin-specific reuptake inhibitors, provide more alternatives for individualizing therapy of patients with major depression.