Improved cognition in Alzheimer's disease with short-term D-cycloserine treatment. A preliminary study of D-cycloserine treatment in Alzheimer's disease. Evaluation of cycloserine in the treatment of Alzheimer's disease. A placebo-controlled trial of D-cycloserine added to conventional neuroleptics in patients with schizophrenia. Placebo-controlled trial of glycine added to clozapine in schizophrenia. D-cycloserine adjuvant therapy to molindone in the treatment of schizophrenia. Placebo-controlled trial of D-cycloserine added to conventional neuroleptics, olanzapine, or risperidone in schizophrenia. D-cycloserine increases positive symptoms in chronic schizophrenic patients when administered in addition to antipsychotics: a double-blind, parallel, placebo-controlled study. D-serine added to clozapine for the treatment of schizophrenia. Four-week nicotine skin patch treatment effects on cognitive performance in Alzheimer's disease. Rivastigmine for dementia associated with Parkinson's disease.
Glutamatergic neurotransmission is important for memory and cognition and is severely affected in Alzheimer's disease. D-Cycloserine exhibits partial agonist activity at the glycine site of N-methyl-D-aspartate subtype glutamate receptor, facilitating activation of the receptor and improving cognition and memory.
                Seventeen patients with Alzheimer's disease received a three-phase, double-blind, placebo-controlled trial of 50 mg and 100 mg/day of D-cycloserine.
                D-Cycloserine was associated with significant improvement in scores on the cognitive subscale of the Alzheimer's Disease Assessment Scale (improvement of 3.0 points) when given at a dose of 100 mg/day.
                D-Cycloserine has cognitive benefits for patients with Alzheimer's disease. D-cycloserine is a partial agonist on the glycine site of the N-methyl-D-aspartate glutamate receptor. This double-blind crossover study of 15 mg D-cycloserine in Alzheimer's disease patients did not demonstrate clinical benefit. Higher medication dosage or long-term treatment may be required. This multicenter study evaluated the efficacy and safety of cycloserine and measured its effects on explicit and implicit memory tests in patients with Alzheimer's disease (AD). Four hundred ten patients with AD, aged 50 years or older, were enrolled in this parallel-group, double-blind, placebo-controlled, randomized trial of 5, 15, or 50 mg cycloserine or placebo twice daily, and 403 entered the double-blind treatment phase. Two hundred sixty-five patients completed the entire 26-week treatment phase. There were no baseline differences among the four treatment groups. Cognitive Drug Research (CDR) efficacy assessments showed no differences between active treatments and placebo from baseline to study weeks 2, 6, 14, or 26. Patients receiving 15 mg of cycloserine improved significantly on one section of an implicit memory test. No differences among treatments were observed for any other assessment scales evaluated. The incidence and severity of adverse events were similar across treatment groups. Cycloserine was well tolerated but did not demonstrate consistent evidence of efficacy during the course of therapy. Higher doses may be necessary to achieve efficacy in the AD population and do not appear to be precluded by the adverse event profile seen in this study. In a preliminary dose-finding study, D-cycloserine, a partial agonist at the glycine modulatory site of the glutamatergic N-methyl-D-aspartate (NMDA) receptor, improved negative symptoms and cognitive function when added to conventional neuroleptics at a dose of 50 mg/d.
                Forty-seven patients with schizophrenia meeting criteria for deficit syndrome were randomized to D-cycloserine, 50 mg/d (n=23) or placebo (n=24) added to their conventional neuroleptic for an 8-week, double-blind trial. Clinical assessments were performed at baseline and at weeks 1, 2, 4, 6, and 8. Serum concentrations of D-cycloserine, relevant amino acids, and homovanillic acid were assayed at baseline and at weeks 4 and 8. A cognitive battery was performed at baseline and at week 8.
                Thirty-nine patients completed the 8-week trial. Seven dropouts occurred in the D-cycloserine group and 1 in the placebo group. The mean reduction in negative symptoms with D-cycloserine (23%) was significantly greater than with placebo (7%) as calculated by slopes representing Scale for the Assessment of Negative Symptoms (SANS) total scores. Improvement of negative symptoms was predicted by low neuroleptic dose and low baseline SANS total score. No differences were found in performance on any cognitive test between groups or in changes in any other clinical measure. Clinical response did not correlate significantly with serum amino acid concentrations at baseline or with concentrations of D-cycloserine at weeks 4 and 8.
                These results support the hypothesis that agents acting at the glycine modulatory site of the NMDA receptor improve primary negative symptoms. The purpose of this study was to evaluate the effects of high-dose oral glycine on positive and negative symptoms and cognitive function when added to clozapine in adults with schizophrenia.
                The authors conducted a double-blind, placebo-controlled, parallel-group trial of 60 g/day of glycine added to clozapine for 8 weeks in 30 adults with schizophrenia. Clinical ratings were performed every 2 weeks.
                Twenty-seven patients completed the trial. Glycine augmentation of clozapine produced no statistically significant change in positive or negative symptoms or cognitive functioning. No subjects showed clinically significant worsening of clinical ratings.
                These data, combined with data from previous trials with D-cycloserine and glycine, suggest that agonists at the glycine site may be less effective when combined with clozapine than they are when combined with conventional antipsychotics. This preliminary investigation examined the therapeutic efficacy of two doses of oral D-cycloserine (5 and 15 mg p.o. b.i.d.) administered as an adjuvant to molindone (150 mg p.o. q.d.) in the treatment of schizophrenia. D-Cycloserine is an agonist at the N-methyl-D-aspartate (NMDA) subclass of glutamate receptor complex. An NMDA agonist intervention was studied because of the schizophreniform psychosis precipitated by phencyclidine (PCP), which is a noncompetitive antagonist at the NMDA glutamate receptor. The PCP model of schizophrenia is regarded as the most comprehensive pharmacological model of this disorder. In this preliminary, placebo-controlled, double-blind, parallel-group study, the measures of treatment efficacy were the Brief Psychiatric Rating Scale, Schedule for the Assessment of Negative Symptoms, and Clinical Global Impression Scale. The final scores for each item of the outcome measures employed were based on the consensus of at least two trained raters who were present during each rating interview. In the 13 subjects evaluated, although the D-cycloserine was well tolerated, neither dose seemed to possess adjuvant therapeutic efficacy. However, since another recent report of nine patients with schizophrenia treated for 2 weeks with a slightly higher dose of D-cycloserine (50 mg/day) described significant clinical and neuropsychological improvement, further study of the adjuvant potential of slightly higher doses of D-cycloserine seems warranted. Additionally, there might be a therapeutic window for D-cycloserine dosing, as daily doses of 250 mg have been associated with symptom worsening. The authors investigated the clinical effects of D-cycloserine when added to treatment with conventional neuroleptics, olanzapine, or risperidone for treatment-resistant schizophrenia.
                Twenty-four patients participated in a double-blind, placebo-controlled, 6-week crossover trial with D-cycloserine, 50 mg/day, added to their fixed dose of antipsychotic medication. Clinical ratings were performed every 2 weeks.
                D-Cycloserine treatment was well tolerated and resulted in a significant reduction in negative symptoms (mean=15%). The degree of improvement did not differ between patients treated with conventional neuroleptics and those treated with olanzapine or risperidone.
                These data support the efficacy of the addition of 50 mg/day of D-cycloserine to treatment with conventional neuroleptics and suggest that therapeutic benefits may also be attained when D-cycloserine is added to olanzapine or risperidone. A hypofunction of the glutamatergic system and NMDA receptors in schizophrenia has been hypothesized. Therefore, stimulation of these receptors could be of benefit to patients with schizophrenia. D-cycloserine has been used for this purpose. This study reports the effects of 100 mg D-cycloserine, when added to typical antipsychotics in chronic schizophrenic patients exhibiting prominent negative symptoms, using a placebo-controlled, double-blind, parallel, design. D-cycloserine slightly worsened psychotic symptoms and general psychopathology as compared to placebo. D-cycloserine failed to change negative symptoms and had no effect on extrapyramidal symptoms. The exacerbation of schizophrenic symptoms may be explained by the antagonistic effects of this dose of D-cycloserine at the glycine recognition site of the NMDA receptor due to competition with the endogenous agonist glycine. Another explanation for the increase in psychopathology may be an interaction with the effects of antipsychotics on NMDA mediated neurotransmission. Thus, D-cycloserine in this study did not ameliorate schizophrenic symptoms. However, the fact that they actually worsened suggests that NMDA systems may be involved in the pathogenesis of schizophrenia. Further placebo-controlled studies with lower dosages of D-cycloserine, preferably in drug-free patients, are necessary to evaluate if D-cycloserine is of use for the treatment of patients with schizophrenia. D-Serine is a full agonist at the glycine site on the N-methyl-D-aspartate (NMDA) receptor. Previous administration of D-serine to schizophrenic patients taking nonclozapine antipsychotics improved positive, negative, and cognitive symptoms, whereas the partial agonist D-cycloserine improved negative symptoms of patients taking conventional antipsychotics but worsened symptoms in clozapine-treated patients. To study the difference between full and partial agonists at the NMDA receptor glycine site, the clinical effects of adding D-serine to clozapine were assessed.
                In a 6-week double-blind trial, 20 schizophrenic patients received placebo or D-serine (30 mg/kg per day) in addition to clozapine. Clinical efficacy, side effects, and serum levels of D-serine were determined every other week.
                The patients exhibited no improvement with D-serine, nor did their symptoms worsen, as previously reported with D-cycloserine.
                The results suggest either that clozapine may have an agonistic effect on the NMDA system or that clozapine-treated patients do not respond to D-serine. Acute nicotine injections have been found to improve attentional performance in patients with Alzheimer's disease (AD), but little is known about chronic nicotine effects.
                The present study was undertaken to evaluate the clinical and neuropsychological effects of chronic transdermal nicotine in Alzheimer's disease subjects over a 4-week period.
                The double-blind, placebo controlled, cross-over study consisted of two 4-week periods separated by a 2-week washout period. Patients wore the nicotine patch (Nicotrol) for 16 h a day at the following doses: 5 mg/day during week 1, 10 mg/day during weeks 2 and 3 and 5 mg/day during week 4. The eight subjects had mild to moderate AD and were otherwise healthy.
                Nicotine significantly improved attentional performance as measured by the Conners' continuous performance test (CPT). There was a significant reduction in errors of omission on the CPT which continued throughout the period of chronic nicotine administration. The variability of hit reaction time (reaction time for correct responses) on the CPT was also significantly reduced by chronic nicotine. Nicotine did not improve performance on other tests measuring motor and memory function.
                The sustained improvement in attention found in this study with nicotine dermal patches is encouraging. However, the lack of detected effects of nicotine treatment on other cognitive and behavioral domains in this study leaves questions concerning the clinical impact of nicotinic treatment in Alzheimer's disease. The modest size of this study limited statistical power which may have been needed to detect more subtle but clinically significant cognitive effects. Higher doses of nicotine, other nicotinic ligands or combination treatment of nicotine with other therapies may be efficacious for producing broader therapeutic effects. Cholinergic deficits are prominent in patients who have dementia associated with Parkinson's disease. We investigated the effects of the dual cholinesterase inhibitor rivastigmine in such patients.
                Patients in whom mild-to-moderate dementia developed at least 2 years after they received a clinical diagnosis of Parkinson's disease were randomly assigned to receive placebo or 3 to 12 mg of rivastigmine per day for 24 weeks. Primary efficacy variables were the scores for the cognitive subscale of the Alzheimer's Disease Assessment Scale (ADAS-cog) and Alzheimer's Disease Cooperative Study-Clinician's Global Impression of Change (ADCS-CGIC). Secondary clinical outcomes were the scores for the Alzheimer's Disease Cooperative Study-Activities of Daily Living, the 10-item Neuropsychiatric Inventory, the Mini-Mental State Examination, Cognitive Drug Research power of attention tests, the Verbal Fluency test, and the Ten Point Clock-Drawing test.
                A total of 541 patients were enrolled, and 410 completed the study. The outcomes were better among patients treated with rivastigmine than among those who received placebo; however, the differences between these two groups were moderate and similar to those reported in trials of rivastigmine for Alzheimer's disease. Rivastigmine-treated patients had a mean improvement of 2.1 points in the score for the 70-point ADAS-cog, from a baseline score of 23.8, as compared with a 0.7-point worsening in the placebo group, from a baseline score of 24.3 (P<0.001). Clinically meaningful improvements in the scores for the ADCS-CGIC were observed in 19.8 percent of patients in the rivastigmine group and 14.5 percent of those in the placebo group, and clinically meaningful worsening was observed in 13.0 percent and 23.1 percent, respectively (mean score at 24 weeks, 3.8 and 4.3, respectively; P=0.007). Significantly better outcomes were seen with rivastigmine with respect to all secondary efficacy variables. The most frequent adverse events were nausea (affecting 29.0 percent of patients in the rivastigmine group and 11.2 percent of those in the placebo group, P<0.001), vomiting (16.6 and 1.7 percent, P<0.001), and tremor (10.2 and 3.9 percent, P=0.01).
                In this placebo-controlled study, rivastigmine was associated with moderate improvements in dementia associated with Parkinson's disease but also with higher rates of nausea, vomiting, and tremor.
                Copyright 2004 Massachusetts Medical Society.
The lack of a positive effect of D-cycloserine on cognitive outcomes in controlled clinical trials with statistical power high enough to detect a clinically meaningful effect means that D-cycloserine has no place in the treatment of patients with Alzheimer's disease.