Tardive dyskinesia exacerbated after ingestion of phenylalanine by schizophrenic patients

Exploring the Role of Nutraceuticals in Major Depressive Disorder (MDD): Rationale, State of the Art and Future Prospects

Major depressive disorder (MDD) is a complex and common disorder, with many factors involved in its onset and development. The clinical management of this condition is frequently based on the use of some pharmacological antidepressant agents, together with psychotherapy and other alternatives in most severe cases. However, an important percentage of depressed patients fail to respond to the use of conventional therapies. This has created the urgency of finding novel approaches to help in the clinical management of those individuals. Nutraceuticals are natural compounds contained in food with proven benefits either in health promotion or disease prevention and therapy. A growing interest and economical sources are being placed in the development and understanding of multiple nutraceutical products. Here, we summarize some of the most relevant nutraceutical agents evaluated in preclinical and clinical models of depression. In addition, we will also explore less frequent but interest nutraceutical products which are starting to be tested, also evaluating future roads to cover in order to maximize the benefits of nutraceuticals in MDD.

A unifying theory for the pathoetiologic mechanism of tardive dyskinesia

INTRODUCTION

Chronic treatment with dopamine D2 receptor antagonists has been proposed to lead to dopamine receptor supersensitivity. Frequently, this is conceptualized as upregulation or changes in the structure or function of the post-synaptic D2 receptor. However, the measured 1.4-fold increase in D2 receptor density and the lack of actual receptor supersensitivity are probably inadequate to explain outcomes such as tardive dyskinesia (TD) and dopamine supersensitivity psychosis.

HYPOTHESIS

Recent data suggest that TD may result from a combination of presynaptic, synaptic, and postsynaptic changes.

DISCUSSION

Presynaptic increase in dopamine release occurs when super-therapeutic blockade of postsynaptic D2 receptors results in excess synaptic unbound dopamine which ultimately ends up being reuptaken by the presynaptic neuron through the dopamine transporter. The increased availability of recycled dopamine results in higher vesicular dopamine concentrations. Since the quantity of neurotransmitter released (known as quanta) is determined by the number of presynaptic neurotransmitter vesicles, the increase in the number (concentration) of dopamine molecules in the vesicles results in a higher concentration of synaptic dopamine with successive depolarization events. Synaptic changes such as the appearance of perforated synapses which is an early step in new synapse formation have been shown in animal models of TD. Finally, postsynaptic increases in D2 receptor expression without demonstration of increased sensitivity or potency has been demonstrated.

CONCLUSION

TD likely develops due to changes across the synapse and terminology such as 'dopamine receptor supersensitivity' can be misleading. 'Synaptic upregulation' may be a more correct term.

Systematic review of interventions for treating or preventing antipsychotic-induced tardive dyskinesia

BACKGROUND

Antipsychotic medication can cause tardive dyskinesia (TD) - late-onset, involuntary, repetitive movements, often involving the face and tongue. TD occurs in > 20% of adults taking antipsychotic medication (first-generation antipsychotics for > 3 months), with this proportion increasing by 5% per year among those who continue to use these drugs. The incidence of TD among those taking newer antipsychotics is not different from the rate in people who have used older-generation drugs in moderate doses. Studies of TD have previously been found to be limited, with no treatment approach shown to be effective.

OBJECTIVES

To summarise the clinical effectiveness and safety of treatments for TD by updating past Cochrane reviews with new evidence and improved methods; to undertake public consultation to gauge the importance of the topic for people living with TD/the risk of TD; and to make available all data from relevant trials.

DATA SOURCES

All relevant randomised controlled trials (RCTs) and observational studies.

REVIEW METHODS

Cochrane review methods, network meta-analysis (NMA).

DESIGN

Systematic reviews, patient and public involvement consultation and NMA.

SETTING

Any setting, inpatient or outpatient.

PARTICIPANTS

For systematic reviews, adults with TD who have been taking a stable antipsychotic drug dose for > 3 months.

INTERVENTIONS

Any, with emphasis on those relevant to UK NHS practice.

MAIN OUTCOME MEASURES

Any measure of TD, global assessments and adverse effects/events.

RESULTS

We included 112 studies (nine Cochrane reviews). Overall, risk of bias showed little sign of improvement over two decades. Taking the outcome of 'TD symptoms improved to a clinically important extent', we identified two trials investigating reduction of antipsychotic dose [n = 17, risk ratio (RR) 0.42, 95% confidence interval (CI) 0.17 to 1.04; very low quality]. Switching was investigated twice in trials that could not be combined (switching to risperidone vs. antipsychotic withdrawal: one RCT, n = 42, RR 0.45, 95% CI 0.23 to 0.89; low quality; switching to quetiapine vs. haloperidol: one RCT, n = 45, RR 0.80, 95% CI 0.52 to 1.22; low quality). In addition to RCTs, six observational studies compared antipsychotic discontinuation with decreased or increased dosage, and there was no clear evidence that any of these strategies had a beneficial effect on TD symptoms (very low-quality evidence). We evaluated the addition to standard antipsychotic care of several treatments, but not anticholinergic treatments, for which we identified no trials. We found no clear effect of the addition of either benzodiazepines (two RCTs, n = 32, RR 1.12, 95% CI 0.6 to 2.09; very low quality) or vitamin E (six RCTs, n = 264, RR 0.95, 95% CI 0.89 to 1.01; low quality). Buspirone as an adjunctive treatment did have some effect in one small study (n = 42, RR 0.53, 95% CI 0.33 to 0.84; low quality), as did hypnosis and relaxation (one RCT, n = 15, RR 0.45, 95% CI 0.21 to 0.94; very low quality). We identified no studies focusing on TD in people with dementia. The NMA model found indirect estimates to be imprecise and failed to produce useful summaries on relative effects of interventions or interpretable results for decision-making. Consultation with people with/at risk of TD highlighted that management of TD remains a concern, and found that people are deeply disappointed at the length of time it has taken researchers to address the issue.

LIMITATIONS

Most studies remain small and poorly reported.

CONCLUSIONS

Clinicians, policy-makers and people with/at risk of TD are little better informed than they were decades ago. Underpowered trials of limited quality repeatedly fail to provide answers.

FUTURE WORK

TD reviews have data from current trials extracted, tabulated and traceable to source. The NMA highlights one context in which support for this technique is ill advised. All relevant trials, even if not primarily addressing the issue of TD, should report appropriate binary outcomes on groups of people with this problem. Randomised trials of treatments for people with established TD are indicated. These should be large (> 800 participants), necessitating accrual through accurate local/national registers, including an intervention with acceptable treatments and recording outcomes used in clinical practice.

STUDY REGISTRATION

This study is registered as PROSPERO CRD4201502045.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Miscellaneous treatments for antipsychotic-induced tardive dyskinesia

BACKGROUND

Antipsychotic (neuroleptic) medication is used extensively to treat people with chronic mental illnesses. Its use, however, is associated with adverse effects, including movement disorders such as tardive dyskinesia (TD) - a problem often seen as repetitive involuntary movements around the mouth and face. This review, one in a series examining the treatment of TD, covers miscellaneous treatments not covered elsewhere.

OBJECTIVES

To determine whether drugs, hormone-, dietary-, or herb-supplements not covered in other Cochrane reviews on TD treatments, surgical interventions, electroconvulsive therapy, and mind-body therapies were effective and safe for people with antipsychotic-induced TD.

SEARCH METHODS

We searched the Cochrane Schizophrenia Group's Study-Based Register of Trials including trial registers (16 July 2015 and 26 April 2017), inspected references of all identified studies for further trials and contacted authors of trials for additional information.

SELECTION CRITERIA

We included reports if they were randomised controlled trials (RCTs) dealing with people with antipsychotic-induced TD and schizophrenia or other chronic mental illnesses who remained on their antipsychotic medication and had been randomly allocated to the interventions listed above versus placebo, no intervention, or any other intervention.

DATA COLLECTION AND ANALYSIS

We independently extracted data from these trials and we estimated risk ratios (RR) or mean differences (MD), with 95% confidence intervals (CIs). We assumed that people who left early had no improvement. We assessed risk of bias and created 'Summary of findings' tables using GRADE.

MAIN RESULTS

We included 31 RCTs of 24 interventions with 1278 participants; 22 of these trials were newly included in this 2017 update. Five trials are awaiting classification and seven trials are ongoing. All participants were adults with chronic psychiatric disorders, mostly schizophrenia, and antipsychotic-induced TD. Studies were primarily of short (three to six6 weeks) duration with small samples size (10 to 157 participants), and most (61%) were published more than 20 years ago. The overall risk of bias in these studies was unclear, mainly due to poor reporting of allocation concealment, generation of the sequence, and blinding.Nineteen of the 31 included studies reported on the primary outcome 'No clinically important improvement in TD symptoms'. Two studies found moderate-quality evidence of a benefit of the intervention compared with placebo: valbenazine (RR 0.63, 95% CI 0.46 to 0.86, 1 RCT, n = 92) and extract of Ginkgo biloba (RR 0.88, 95% CI 0.81 to 0.96, 1 RCT, n = 157), respectively. However, due to small sample sizes we cannot be certain of these effects.We consider the results for the remaining interventions to be inconclusive: Low- to very low-quality evidence of a benefit was found for buspirone (RR 0.53, 95% CI 0.33 to 0.84, 1 RCT, n = 42), dihydrogenated ergot alkaloids (RR 0.45, 95% CI 0.21 to 0.97, 1 RCT, n = 28), hypnosis or relaxation, (RR 0.45, 95% CI 0.21 to 0.94, 1 study, n = 15), pemoline (RR 0.48, 95% CI 0.29 to 0.77, 1 RCT, n = 46), promethazine (RR 0.24, 95% CI 0.11 to 0.55, 1 RCT, n = 34), insulin (RR 0.52, 95% CI 0.29 to 0.96, 1 RCT, n = 20), branched chain amino acids (RR 0.79, 95% CI 0.63 to 1.00, 1 RCT, n = 52), and isocarboxazid (RR 0.24, 95% CI 0.08 to 0.71, 1 RCT, n = 20). There was low- to very low-certainty evidence of no difference between intervention and placebo or no treatment for the following interventions: melatonin (RR 0.89, 95% CI 0.71 to 1.12, 2 RCTs, n = 32), lithium (RR 1.59, 95% CI 0.79 to 3.23, 1 RCT, n = 11), ritanserin (RR 1.00, 95% CI 0.70 to 1.43, 1 RCT, n = 10), selegiline (RR 1.37, 95% CI 0.96 to 1.94, 1 RCT, n = 33), oestrogen (RR 1.18, 95% CI 0.76 to 1.83, 1 RCT, n = 12), and gamma-linolenic acid (RR 1.00, 95% CI 0.69 to 1.45, 1 RCT, n = 16).None of the included studies reported on the other primary outcome, 'no clinically significant extrapyramidal adverse effects'.

AUTHORS' CONCLUSIONS

This review has found that the use of valbenazine or extract of Ginkgo biloba may be effective in relieving the symptoms of tardive dyskinesia. However, since only one RCT has investigated each one of these compounds, we are awaiting results from ongoing trials to confirm these results. Results for the remaining interventions covered in this review must be considered inconclusive and these compounds probably should only be used within the context of a well-designed evaluative study.

Miscellaneous treatments for neuroleptic-induced tardive dyskinesia

BACKGROUND

Tardive dyskinesia is a disabling movement disorder associated with the prolonged use of neuroleptic medication. This review, one in a series examining the treatment of tardive dyskinesia, will cover miscellaneous treatments not covered elsewhere.

OBJECTIVES

To determine whether the following interventions were associated with a reduction of neuroleptic induced tardive dyskinesia: botulin toxin, endorphin, essential fatty acid, EX11582A, ganglioside, insulin, lithium, naloxone, oestrogen, periactin, phenylalanine, piracetam, stepholidine, tryptophan, neurosurgery, or ECT.

SEARCH STRATEGY

The initial search of Biological Abstracts (1982-1995), The Cochrane Schizophrenia Group's Register (January 1996), EMBASE (1980-1995), LILACS (1982-1996), MEDLINE (1966-1995) and PsycLIT (1974-1995) was updated by searching Cochrane Schizophrenia Group's Register in July 2002. References of all relevant studies were searched for further trial citations. Principal authors of trials were contacted.

SELECTION CRITERIA

Studies were selected if they focused on people with schizophrenia or other chronic mental illnesses, with neuroleptic-induced tardive dyskinesia and compared the use of the interventions listed above versus placebo or no intervention.

DATA COLLECTION AND ANALYSIS

Studies were reliably selected, quality assessed and data extracted. Data were excluded where more than 50% of participants in any group were lost to follow up. For binary outcomes a random effects risk ratio (RR) and its 95% confidence interval (CI) was calculated. Where possible, the weighted number needed to treat/harm statistic (NNT/H), and its 95% confidence interval (CI), was also calculated. For continuous outcomes, endpoint data were preferred to change data. Non-skewed data from valid scales were to have been synthesised using a weighted mean difference (WMD).

MAIN RESULTS

Fifty-seven references describing 37 different trials were identified by the search strategy. Seven of these were included, 27 excluded, and three await assessment. Ceruletide was not clearly more effective than placebo (n=132, 2 RCTs, RR not any improvement in tardive dyskinesia 0.82 CI 0.6 to 1.1). This also applied to gamma-linolenic acid, although data were sparse (n=16, 1 RCT, RR no clinical improvement 1.00 CI 0.7 to 1.5), oestrogen (n=12, 1 RCT, RR no clinically important improvement 1.2 CI 0.8 to 1.7), and lithium (n=11, 1 RCT, RR no clinically important improvement 1.39 CI 0.6 to 3.1). Phenylalanine may even be detrimental (n=18, 1 RCT, MD AIMS score 4.40 CI 1.16 to 7.64). One small study (n=20) found that insulin was more likely to produce a clinical improvement in tardive dyskinesia than placebo (RR no clinical improvement 0.5 CI 0.3 to 0.9, NNT 2 CI 1 to 5).

REVIEWER'S CONCLUSIONS

There is no strong evidence to support the everyday use of any of the agents included in this review. All results must be considered inconclusive and these compounds probably should only be used within the context of a well-designed evaluative study.

Assessment of the safety of glutamine and other amino acids

Glutamine is used to supplement intravenous and enteral feeding. Although there have been many human studies of its efficacy, there have been very few studies with safety as a primary goal. This article analyzes the literature on the safety of glutamine and also examines the available information on high intakes of total protein and other amino acids, so that additional indicators of potentially adverse effects can be suggested. Four studies that specifically addressed glutamine safety were identified, from which it was concluded that glutamine is safe in adults and in preterm infants. However, the published studies of safety have not fully taken account of chronic consumption by healthy subjects of all age groups. To help identify potential undetected hazards of glutamine intake, the literature on adverse effects of high dietary intake of protein and other amino acids was examined. High protein is reputed to cause nausea, vomiting and ultimately death in adults, and has been shown to result in neurological damage in preterm infants. Individual amino acids cause a variety of adverse effects, some of them potentially fatal, but neurological effects were the most frequently observed. Because glutamine is metabolized to glutamate and ammonia, both of which have neurological effects, psychological and behavioral testing may be especially important.

The association between risk factors for tardive dyskinesia and phenylalanine-induced abnormal movements in schizophrenia

We examined whether an oral challenge dose of the amino acid phenylalanine (a dopamine precursor) exacerbates the abnormal movements of tardive dyskinesia (TD). We also examined age, gender, treatment duration, and baseline movement severity in relation to phenylalanine-induced changes in movements. Lastly, we assessed the influence of fasting amino acid levels on phenylalanine-induced movements. In a placebo-controlled fashion, the abnormal involuntary movement scale (AIMS) was obtained on 25 patients before and after a phenylalanine challenge drink. A general linear model determined the relative effects of age, gender, treatment duration, and fasting amino acid levels on the magnitude of induced movements. Age and treatment duration did not affect phenylalanine-induced movements. Lower fasting levels of phenylalanine were associated with greater movements after controlling for age, F = 11.89, p < 0.003. The severity of abnormal movements at baseline also predicted response to phenylalanine, F = 8.62, p = 0.0079. Brain amino acid and neurotransmitter pools are influenced by changes in dietary protein, which may have implications in the development and prevention of movement disorders. This study suggests that fasting amino acid levels may predict differences in vulnerability to movements during an influx of neurotransmitter precursors, perhaps due to long-term compensatory changes in receptor sensitivity. Copyright 2001 John Wiley & Sons, Ltd.