The cognitive cost of anticholinergic burden: decreased response to cognitive training in schizophrenia

OBJECTIVE

Schizophrenia is treated with medications that raise serum anticholinergic activity and are known to adversely affect cognition. The authors examined the relationship between serum anticholinergic activity and baseline cognitive performance and response to computerized cognitive training in outpatients with schizophrenia.

METHOD

Fifty-five patients were randomly assigned to either computerized cognitive training or a computer games control condition. A neurocognitive battery based on the Measurement and Treatment Research to Improve Cognition in Schizophrenia (MATRICS) initiative was performed at baseline and after the intervention. Serum anticholinergic activity, measured at study entry by radioreceptor assay, was available for 49 patients.

RESULTS

Serum anticholinergic activity showed a significant negative correlation with baseline performance in verbal working memory and verbal learning and memory, accounting for 7% of the variance in these measures, independent of age, IQ, or symptom severity. Patients in the cognitive training condition (N=25) showed a significant gain in global cognition compared to those in the control condition, but this improvement was negatively correlated with anticholinergic burden. Serum anticholinergic activity uniquely accounted for 20% of the variance in global cognition change, independent of age, IQ, or symptom severity.

CONCLUSIONS

Serum anticholinergic activity in schizophrenia patients shows a significant association with impaired performance in MATRICS-based measures of verbal working memory and verbal learning and memory and is significantly associated with a lowered response to an intensive course of computerized cognitive training. These findings underscore the cognitive cost of medications that carry a high anticholinergic burden. The findings also have implications for the design and evaluation of cognitive treatments for schizophrenia.

Sex, race, and smoking impact olanzapine exposure

Response to antipsychotics is highly variable, which may be due in part to differences in drug exposure. The goal of this study was to evaluate the magnitude and variability of concentration exposure of olanzapine. Patients with Alzheimer's disease (n = 117) and schizophrenia (n = 406) were treated with olanzapine as part of the Clinical Antipsychotic Trials of Intervention Effectiveness (CATIE). Combined, these patients (n = 523) provided 1527 plasma samples for determination of olanzapine concentrations. Nonlinear mixed-effects modeling was used to determine the population pharmacokinetics of olanzapine, and patient-specific covariates were evaluated as potential contributors to variability in drug exposure. The population mean olanzapine clearance and volume of distribution were 16.1 L/h and 2150 L, respectively. Elimination of olanzapine varied nearly 10-fold (range, 6.66-67.96 L/h). Smoking status, sex, and race accounted for 26%, 12%, and 7% of the variability, respectively (P < .0001). Smokers cleared olanzapine 55% faster than non/past smokers (P < .0001). Men cleared olanzapine 38% faster than women (P < .0001). Patients who identified themselves as black or African American cleared olanzapine 26% faster than other races (P < .0001). Differences in olanzapine exposure due to sex, race, and smoking may account for some of the variability in response to olanzapine.

Serum anticholinergic activity and motor performance in elderly persons

BACKGROUND

Medications prescribed to elderly persons often have an anticholinergic effect, as do many commonly used over-the-counter drugs. Anticholinergic medications are known to produce psychomotor slowing, especially in older persons.

METHODS

The present study examined whether the cumulative anticholinergic load present in the serum of community volunteers was associated with decrements on tests of psychomotor performance (gait speed and simple manual response time) known to predict falls in elderly persons.

RESULTS

Serum anticholinergic activity (SAA) was relatively low in this group; however, an elevated SAA was associated with a significant slowing in both gait speed and simple response time.

CONCLUSION

Cumulative anticholinergic burden may be one of the factors contributing to an increased risk of falls in the older population.

A model of anticholinergic activity of atypical antipsychotic medications

BACKGROUND

Atypical antipsychotics clozapine, olanzapine, and quetiapine have significant affinity for the muscarinic receptors in vitro, while aripiprazole, risperidone, and ziprasidone do not. Dissimilarity in binding profiles may contribute to the reported differences in the anticholinergic effects of these antipsychotics. However, it is difficult with the available data to predict the likelihood of anticholinergic effects occurring with various doses of an atypical antipsychotic.

METHODS

We developed a model to assess the potential anticholinergic activity (AA) of atypical antipsychotics at therapeutic doses. A radioreceptor assay was used to measure in vitro AA at 6 clinically relevant concentrations of aripiprazole, clozapine, olanzapine, quetiapine, risperidone, and ziprasidone. Using published pharmacokinetic data, in combination with the measured in vitro AA, dose-AA curves were generated.

RESULTS

Clozapine, and to a lesser extent olanzapine and quetiapine showed dose-dependent increases in AA. At therapeutic doses, the AA (in pmol/mL of atropine equivalents) was estimated to range from 27-250, 1-15, and 0-5.4 pmol/mL for clozapine, olanzapine, and quetiapine, respectively. Aripiprazole, risperidone, and ziprasidone did not demonstrate AA at any of the concentrations studied.

CONCLUSIONS

Therapeutic doses of clozapine, olanzapine, and, to a lesser extent, quetiapine are associated with clinically relevant AA.

Population pharmacokinetics as a method to detect variable risperidone exposure in patients suffering from dementia with behavioral disturbances

OBJECTIVE

This study was intended to compare the consistency of risperidone exposure in patients who have dementia and behavioral disturbances treated in a psychiatric hospital versus a community care setting.

METHODS

Population pharmacokinetic modeling was used to assess the consistency of risperidone exposure in Alzheimer's disease patients with agitation. The ratio of predicted to observed drug concentrations (Cpred/Cobs) derived from this model was used to compare exposure in the inpatient versus long-term/home care settings using both the mean and the variance of this term across groups.

RESULTS

The modeled Cpred/Cobs ratios had a much higher within-subject variance in the inpatients than in the community care patients (117.03% vs 72.35%; P < 0.001). The central tendencies of the Cpred/Cobs ratios across the 2 groups were not significantly different.

CONCLUSIONS

Exposure to risperidone was more variable in a psychiatric hospital than in a community care setting. Future research may help to identify the specific contributors to the increased variance observed in this pilot study.

Utility of sparse concentration sampling for citalopram in elderly clinical trial subjects

The objective of this study was to evaluate whether the disposition of the selective serotonin reuptake inhibitor, citalopram, could be robustly captured using 1 to 2 concentration samples per subject in 106 patients participating in 2 clinical trials. Nonlinear mixed-effects modeling was used to evaluate the pharmacokinetic parameters describing citalopram's disposition. Both a prior established 2-compartment model and a de novo 1-compartment pharmacokinetic model were used. Covariates assessed were concomitant medications, race, sex, age (22-93 years), and weight. Covariates affecting disposition were assessed separately and then combined in a stepwise manner. Pharmacokinetic characteristics of citalopram were well captured using this sparse sampling design. Two covariates (age and weight) had a significant effect on the clearance and volume of distribution in both the 1- and 2-compartment pharmacokinetic models. Clearance decreased 0.23 L/h for every year of age and increased 0.14 L/h per kilogram body weight. It was concluded that hyper-sparse sampling designs are adequate to support population pharmacokinetic analysis in clinically treated populations. This is particularly valuable for populations such as the elderly, who are not typically available for pharmacokinetic studies.

alpha1-acid glycoprotein in late-life depression: relationship to medical burden and genetics

Serum alphal-acid glycoprotein (AAG) concentrations were examined in relationship to age, medical burden, depression, and mental status in elderly control (n = 19, mean age = 72.1 +/- 6.8 years) and depressed (n = 58, mean age = 71.9 +/- 7.1 years) subjects. DNA was analyzed for allelic variants of the AGP1 (ORM1) gene in both groups. Depressed subjects' AAG serum levels were measured at baseline and after 6 weeks of antidepressant treatment. Before treatment, depressed subjects had significantly higher serum AAG concentrations than nondepressed controls (t49.2 = -3.48, P = .0011). Pretreatment AAG levels also correlated with degree of medical burden, measured by the Cumulative Illness Rating Scale-Geriatrics (r = 0.28, P = .0303), but not with age, depression severity, or cognitive scores. There was no significant difference between responders and nonresponders on changes in AAG levels from baseline to week 6. Frequency differences in ORM1 allelic variants apparently did not influence increased AAG concentrations in depressed patients.

Risperidone and 9-hydroxyrisperidone concentrations are not dependent on age or creatinine clearance among elderly subjects

Risperidone is extensively metabolized to an active metabolite, 9-hydroxyrisperidone (9-OH), which is dependent on renal clearance. Risperidone and 9-OH clearances are reduced in the elderly when compared to young subjects. The objective of this study was to determine whether among elderly subjects, risperidone and 9-OH clearance would further decline with increasing age and decreasing creatinine clearance (CrCl). Twenty geriatric inpatients were evaluated in a naturalistic setting with regard to total daily risperidone dose and dosing interval. Creatinine clearance was determined using an 8-hour urine collection. Risperidone and 9-OH concentrations were determined by radioimmunoassay. Spearman's correlation coefficients were used to examine the impact of age and CrCl on concentrations of risperidone, 9-OH, their sum, and the quotient of 9-OH/risperidone. Mean age was 76.4 +/- 9 years (range 56-91). Mean CrCl was 55.4 +/- 32.8 mL/min/1.73 m2 (range 17-142 mL/min/1.73 m2). Mean risperidone daily dose was 1.3 +/- 0.7 mg. Steady-state risperidone and 9-OH concentrations were 4.1 +/- 5.3 ng/mL and 9.1 +/- 6.2 ng/mL, respectively. Mean 9-OH/risperidone was 6.2 +/- 6.1. Concentrations of risperidone, 9-OH, their sum, and 9-OH/risperidone were not significantly correlated with age or CrCl. These results were unchanged when concentrations were corrected for total daily risperidone dose. Among elderly subjects, risperidone and 9-OH clearance do not decline with increasing age or declining CrCl.

A preliminary study of the effect of fluoxetine treatment on the 2:16-alpha-hydroxyestrone ratio in young women

Cytochrome P450 isoenzymes are known to contribute to estrone metabolism. The authors hypothesized that fluoxetine, a known inhibitor of multiple P450 isoenzymes including 3A4, 2C9, and 2D6, would affect estrone metabolism, altering the 2-hydroxyestrone:16-alpha-hydroxyestrone (2OHE1:16OHE1) ratio. In this preliminary study, four of eight recruited women with regular menstrual cycles, aged 21-37 years, completed a 24-hour urine collection prior to initiation of fluoxetine therapy and after at least 5 weeks of antidepressant treatment. In three of the four women who were nonsmokers, the 2OHE1:16OHE1 ratio was significantly higher after 5 weeks of fluoxetine therapy (pretreatment, 2.08 +/- 0.11; posttreatment, 3.50 +/- 0.46; paired Student's t-test P = 4.72, P = 0.021).

CYP2D6 genotyping with oligonucleotide microarrays and nortriptyline concentrations in geriatric depression

Recent advances in oligonucleotide microarray technology ("gene chips") permit rapid screening for DNA sequence variation. The CYP2D6 gene encodes debrisoquine hydroxylase, which metabolizes the antidepressant nortriptyline and other psychotropic medications. Nortriptyline plasma concentrations were obtained after at least three weeks of treatment in 36 geriatric patients with major depression who were taking a mean of 8.6 other medications besides nortriptyline. Oligonucleotide microarrays were used to detect 16 CYP2D6 alleles that affect debrisoquine hydroxylase activity. Subjects carrying alleles encoding impaired debrisoquine hydroxylase activity had significantly greater nortriptyline concentrations and lower nortriptyline doses than did other subjects. Significant correlations were found between the numbers of alleles encoding decreased metabolism and nortriptyline plasma concentration, nortriptyline dose, and nortriptyline plasma concentration standardized for dose, indicating a gene dosage effect. These results demonstrate that CYP2D6 genotyping on a microarray platform can be used to predict plasma antidepressant concentrations despite advanced patient age and numerous concurrent medications.

Antipsychotic radioreceptor assay: a modification identifying selective receptor effects

Radioreceptor assays offer the advantage of a single assay that can assess uniform exposure to multiple chemical compounds. The advent of atypical antipsychotic agents has led to new awareness of the multiple receptor subtypes through which antipsychotic agents may exert their effects, and a renewed interest in comparative drug trials of antipsychotics. The objective of this study was to show the development and validation of antipsychotic radioreceptor assays using clonal cell lines stably expressing isolated human receptors. Model assays were developed using the dopamine(2) (D(2)) and D(4) receptors. D(2) and D(4) activities measured by radioreceptor assay in plasma of antipsychotic-treated subjects were highly correlated with high-performance liquid chromatography determinations of antipsychotic concentrations. Similarly, for a variety of typical and atypical antipsychotic agents, the quotients of D(4)/D(2) activity in plasma of antipsychotic-treated subjects were highly correlated with the quotients of D(4)/D(2) affinities of these agents. Valid receptor-selective antipsychotic assays can be established and may have utility for dissecting the in vivo activity of atypical antipsychotics in relation to specific outcomes in clinical trials.

Low-level serum anticholinergicity as a source of baseline cognitive heterogeneity in geriatric depressed patients

Depressed geriatric patients show substantial intersubject variability in cognitive performance, which complicates attempts to evaluate the cognitive effects of depression and of antidepressant therapy. This variability may reflect the multiple medications older patients take, many of which have anticholinergic effects. This study examined whether serum anticholinergicity (SA) explained some of the variability in depressed geriatric patients' memory performance. Before starting antidepressant treatment, 36 elderly depressed subjects were given a verbal learning test. At the same time, a blood sample was taken and analyzed by radioreceptor binding assay to determine their SA level. Nineteen of the subjects had detectable levels (mean = 0.28 pmole atropine equivalent). Subjects with an SA of zero showed significantly better delayed recall than did those with a positive SA level. Thus, even very low SA may produce subtle decrements in memory performance, an area of cognition known to be highly sensitive to anticholinergic effects.

Allelic variation in the serotonin transporter promoter affects onset of paroxetine treatment response in late-life depression

The relationship of the serotonin transporter gene promoter region polymorphism (5-HTTLPR) to antidepressant response was examined in 95 elderly patients receiving a protocolized treatment for depression with paroxetine or nortriptyline. Patients were treated for up to 12 weeks and assessed weekly with clinical ratings and measurements of plasma drug concentrations. Twenty-one of the paroxetine-treated subjects were found to have the ll genotype and 30 had at least one s allele. There were no baseline differences between these groups in pretreatment Hamilton Rating Scale for Depression (HRSD) scores or anxiety symptoms. During acute treatment with paroxetine, mean reductions from baseline in HRSD were significantly more rapid for patients with the ll genotype than for those possessing an s allele, despite equivalent paroxetine concentrations. Onset of response to nortriptyline was not affected. Allelic variation of 5-HTTLPR may contribute to the variable initial response of patients treated with a selective serotonin reuptake inhibitor.

Anticholinergic differences among patients receiving standard clinical doses of olanzapine or clozapine

This study evaluated anticholinergic effects among patients with schizophrenia, schizoaffective disorder, or bipolar I disorder who were receiving either olanzapine (N = 12) or clozapine (N = 12) at standard clinical doses in a naturalistic setting. Serum anticholinergic levels were determined in adult male and female subjects using a radioreceptor binding assay. The Udvalg for Kliniske Undersogelser Scale was used to evaluate anticholinergic side effects clinically, and the Mini-Mental State Examination provided a global cognitive measure. Patients had achieved target doses that were stable at the time at which blood samples were obtained, and no other concomitant medicine with known anticholinergic potential was allowed. Patients receiving olanzapine (average dose, 15 mg/day) had serum anticholinergic levels of 0.96 (+/-0.55) pmol/ atropine equivalents compared with levels of 5.47 (+/-3.33) pmol/atropine equivalents for those receiving clozapine (average dose, 444 mg/day) (p < 0.001). Rates of increased and decreased salivation were significantly more common among the clozapine- and olanzapine-treated patients, respectively, whereas constipation, urinary disturbances, and tachycardia/palpitations were significantly more common among clozapine-treated patients. Neither group showed any global cognitive deficits. Olanzapine-treated patients had serum anticholinergic levels that were less than one fifth those of the clozapine-treated patients. Furthermore, clinical evaluations confirmed that clozapine-treated patients experienced more frequent and severe anticholinergic side effects (except dry mouth). However, none of the patients in either group expressed any desire to discontinue these medications as a result of the anticholinergic side effects.

Inhibition of caffeine metabolism by estrogen replacement therapy in postmenopausal women

This study was conducted to investigate the effect of therapeutic estrogen on cytochrome P450 1A2-mediated metabolism in postmenopausal women using caffeine as a model substrate. Twelve healthy postmenopausal women underwent estrogen replacement therapy in the form of estradiol (Estrace). Estradiol was initiated at a dose of 0.5 mg a day and titrated to achieve a steady-state plasma concentration of 50 to 150 pg/ml. Caffeine metabolic ratios (CMR; paraxanthine/caffeine) were assessed both before and after 8 weeks of estrogen replacement. For the 12 subjects, there was a mean reduction in CMR of -29.2 +/- 25.0 (p = 0.0019). Consistent with previous results found in younger women, these results indicate that exogenous estrogen in older women may inhibit CYP1A2-mediated caffeine metabolism.

Serum anticholinergicity in elderly depressed patients treated with paroxetine or nortriptyline

OBJECTIVE

The authors' goal was to compare serum anticholinergicity of 61 elderly depressed patients randomly assigned to double-blind treatment with paroxetine (N=31) or nortriptyline (N=30).

METHOD

Both antidepressants were titrated in a standardized manner, and plasma was sampled weekly for measurement of paroxetine and nortriptyline and its hydroxy metabolite concentrations. Serum anticholinergicity was measured at baseline and after 1, 4, and 6 weeks of treatment. Side effects were assessed by using a validated scale.

RESULTS

After correcting for pretreatment anticholinergicity, the authors found that mean serum anticholinergicity for the nortriptyline-treated patients was significantly greater than that for the paroxetine group at all weeks assessed. Serum anticholinergicity was significantly correlated with nortriptyline but not with paroxetine plasma levels. Complaints of dry mouth and tachycardia were significantly more frequent and severe in the nortriptyline group.

CONCLUSIONS

These findings suggest that, at therapeutic plasma concentrations, paroxetine has approximately one-fifth the anticholinergic potential of nortriptyline in older patients.

Plasma levels of citalopram enantiomers and metabolites in elderly patients

Ten patients with dementia and significant behavioral disturbances (mean age of 77.2 +/- 8.2 years) received citalopram, 10 mg/day for 3 days, followed by 20 mg/day for 2 weeks. Six of the 10 patients completing 17 days of treatment had a clinically impressive response, as assessed by significant improvement in six target items on the Neurobehavioral Rating Scale. Eight patients were also analyzed by measuring the racemic and enantiomeric plasma levels of citalopram (CIT) and desmethylcitalopram (DCIT). A sensitive high-performance liquid chromatography (HPLC) assay for citalopram enantiomers and metabolites was developed using ultraviolet detection. The lower limit of detection was 10 ng/ml for each enantiomer. Steady-state plasma level ranges were 11.2 to 92.2 ng/ml for the biologically active S(+) citalopram and 12.8 to 95.7 ng/ml for the inactive R(-) enantiomer. For the S and R enantiomers of desmethylcitalopram, plasma levels ranged from 11.0 to 22.0 ng/ml and 9.2 to 22.0 ng/ml, respectively. The racemic citalopram plasma level to dose ratio of 3.50 was higher than the ratio (1.96) reported by Overo (1982) for 55 younger patients. The stereoselective metabolism of the enantiomers for citalopram and desmethylcitalopram (S(+) and R(-) enantiomers) in these older subjects differed from that reported in younger patients, suggesting possible age-associated changes in CYP2C19 activities. We hypothesize that quantification of S(+) citalopram will permit a more accurate examination of dose/response relationships. This measure seems to be especially important for older subjects, given the wide ranges and higher concentrations evident from our preliminary results.

An open pilot study of citalopram for behavioral disturbances of dementia. Plasma levels and real-time observations

Citalopram, in European studies, has shown some early promise for treatment of poststroke depression and behavioral complications of dementia. An open pilot study of citalopram was conducted in 16 patients with dementia and behavioral disturbances. Citalopram was well tolerated by 13 of the patients, and 9 had a clinically impressive response. A significant overall mean reduction in disruptive vocalizations was observed by means of a novel technique of computer-assisted real-time observation. The mean citalopram plasma level-to-dose ratio was found to be twice that previously reported in younger patients. These pilot findings should encourage future placebo concentration-controlled trials.

Quantitative determination of perphenazine and its metabolites in plasma by high-performance liquid chromatography and coulometric detection

An accurate, reliable method has been developed for the therapeutic monitoring of perphenazine (PPZ) and its major metabolites in human plasma samples. Steady-state plasma levels of PPZ and its metabolites were quantitated for 30 elderly patients (mean age: 75) undergoing concurrent treatment with nortriptyline (NT) and PPZ, doses ranging from 4 to 32 mg/day for PPZ. The assay was suitable with patients on concurrent medications, and smaller patient plasma volumes (1 ml) were used indicating sufficient sensitivity and specificity. After plasma extraction and separation on a Nucleosil 5-microns C18 column, the recoveries (mean +/- S.D.) of PPZ and its metabolites were determined; perphenazine 92 +/- 7.5%, deshydroxyethylperphenazine 81 +/- 7.2%, perphenazine sulfoxide 68 +/- 6.4%, and 7-hydroxyperphenazine 45 +/- 5.5%. The assay also had limits of quantitative detectability for PPZ and its metabolites as follows: perphenazine 0.5 ng/ml, deshydroxyethylperphenazine 1.0 ng/ml, perphenazine sulfoxide 0.5 ng/ml, and 7-hydroxyperphenazine 5 ng/ml. Inter-assay reproducibility (C.V.) for the quality controls and patient samples ranged from 18.8 to 2.4%. The sensitivity and reproducibility of this method should improve PPZ therapeutic drug monitoring and research on interactions in depressed geriatric patients.