Discontinuation of thioridazine in patients with learning disabilities: balancing cardiovascular toxicity with adverse consequences of changing drugs

Withdrawal of antipsychotic drugs from adults with intellectual disabilities

Objectives: There is a view that antipsychotic drugs can be successfully withdrawn from people with intellectual disabilities with resultant health gain. This study critically examines whether antipsychotic drug withdrawal is beneficial.

Methods: 119 adults with intellectual disabilities were included in a programme of antipsychotic drug withdrawal.

Results: The clinical outcomes of this programme are poor. Only 7.6% completely withdrew from antipsychotic drugs, and 48.7% experienced onset/deterioration in problem behaviours or mental ill-health. Significant drug side effects with the introduction of new drugs were experienced by 23.3%. Resultant mean antipsychotic drug doses were higher compared with those at the start of the programme. The cost to the intellectual disabilities psychiatric service (over and above that of routine psychiatric care) was £258,050 (€391,693), and the human cost was considered high. Primary care, social care and family costs were not calculated. The only specific factors found to be associated with poor outcome were increased severity of intellectual disabilities and female gender.

Conclusions: The successful role of antipsychotic drugs in the management of problem behaviours in people who do not have verbal communication skills may relate to the pathoplastic effect of intellectual disabilities on clinical presentation, with problem behaviours being markers of eg. psychosis and anxiety disorders. Our original findings challenge the view that routine withdrawal of antipsychotic drugs is good practice; we reinterpret the existing literature, and recommend caution and vigilance in pharmacotherapy.

Outcome of patients after market withdrawal of thioridazine: a retrospective analysis in a nationwide cohort

OBJECTIVE

Thioridazine is a first-generation antipsychotic drug that was withdrawn from the market worldwide in 2005. The outcome of clinically stable schizophrenia patients who used thioridazine before market withdrawal was evaluated.

METHODS

Nationwide registers in Finland were utilized to study thioridazine use, hospitalization rate and length of hospital stay.

RESULTS

Although thioridazine use continued to diminish year after year, the hospitalization rate remained constant until the withdrawal year of 2005, when the percentage of patients hospitalized for schizophrenia doubled.

CONCLUSION

The market withdrawal of thioridazine predisposed many stable patients towards psychotic relapses. In order to minimize this kind of risk, an overall risk-benefit assessment and a clear-cut plan for the replacement of an antipsychotic should be established before market withdrawal.

Nature and quality of antipsychotic prescribing practice in UK psychiatry of intellectual disability services

BACKGROUND

Antipsychotics are perceived to be over-used in the management of behavioural problems in people with an intellectual disability (ID). Published guidelines have set good practice standards for the use of these drugs for behavioural indications. We sought to identify the range of indications for which antipsychotic drugs are prescribed in people with ID and to audit clinical practice against the standards.

METHOD

Data were collected from the clinical records of individuals with ID who were under the care of mental health services in the UK, and prescribed an antipsychotic drug.

RESULTS

The sample comprised 2319 patients from 39 clinical services. Twenty-seven per cent of the patients had a diagnosis of a psychotic illness (ICD-10 F20-29) and 27% an affective illness (ICD-10 F30-39). The proportion who did not have a psychiatric diagnosis ranged from 6% of those with borderline/mild ID to 21% of those with severe/profound ID. Overall, the most common indications for prescribing an antipsychotic drug were comorbid psychotic illness, anxiety and agitation, and a range of behavioural disturbances. The prevalence of use of antipsychotic drugs to manage challenging behaviour in the absence of concomitant mental illness increased with the severity of ID and accounted for almost half of prescriptions in those with severe/profound ID. Adherence to the audit standards related to documentation of clinical indications and review of efficacy was high. Side effect monitoring was less assiduous.

CONCLUSIONS

In clinical practice, most prescriptions for antipsychotic drugs in people with ID are consistent with the evidence base and the overall quality of prescribing practice, as measured against recognised standards, is good, although in some patients potentially remedial side effects may not be detected and treated.

Mechanisms of action of antipsychotic drugs of different classes, refractoriness to therapeutic effects of classical neuroleptics, and individual variation in sensitivity to their actions: Part II

Rapid-onset psychotic rebound is uncommon on discontinuation of most antipsychotic drugs, as might be expected for antipsychotic drugs with (hypothetically) indirect actions at their final target receptors. Rapid-onset psychosis is more common on withdrawal of clozapine, which might be expected if its action is direct. Drugs other than clozapine (notably thioridazine) may have hitherto unrecognised similarities to clozapine (but without danger of agranulocytosis), and may be useful in treatment of refractory psychosis. Quetiapine fulfils only some criteria for a clozapine-like drug. Clinical response to neuroleptics varies widely at any given plasma level. Haase's "neuroleptic threshold" concept suggests that the dose producing the slightest motor side effects produces most or all of the therapeutic benefit, but analyses presented here suggest that antipsychotic actions are not subject to a sharp "all-or-none" threshold but increase over a small dose range. This concept could provide a method for quantitative determination of individualized optimal doses.

Repeated dosing with donepezil does not affect the safety, tolerability or pharmacokinetics of single-dose thioridazine in young volunteers

AIM

To investigate the effects of donepezil at steady state on the safety, tolerability and pharmacokinetics of a single dose of thioridazine, in healthy subjects.

METHODS

An open, two-way, balanced crossover study, in 12 subjects (six men and six women) aged 19-41 years. During both treatment periods, subjects received a single oral dose of 50 mg thioridazine; in one period the thioridazine was given alone, and in the other period it was given together with the last of 15 daily, oral doses of donepezil 5 mg. The 'washout' periods were 1 week when thioridazine was given first, and 2 weeks when thioridazine was given last. Plasma concentrations of thioridazine were measured after each dose, and pharmacokinetic parameters were determined. Interactions were tested by using an equivalence analysis in which thioridazine was the 'Reference' and thioridazine + donepezil the 'Test' regimen. Safety and tolerability were monitored.

RESULTS

Donepezil had no marked effect on the pharmacokinetics of thioridazine, as judged by the equivalence analysis of AUC(0-tn), AUC(0-infinity), t((1/2)) and t(max). C(max) was very similar in the 'Test' and 'Reference' regimens, but the confidence intervals were too wide to confirm equivalence. Donepezil was well tolerated, whereas thioridazine was associated with light-headedness, tiredness and postural hypotension, irrespective of whether or not donepezil was given concurrently.

CONCLUSIONS

Repeated dosing with donepezil, 5 mg daily for 2 weeks, had no significant effect on the safety, tolerability or pharmacokinetics of thioridazine. Thioridazine was poorly tolerated.

Electrocardiogram and cardiovascular changes in thioridazine and chlorpromazine poisoning

OBJECTIVES

To examine the effects of anti-psychotic medications on cardiovascular parameters in overdose. Specifically, to examine dose-response relationships for thioridazine and chlorpromazine.

METHODS

A retrospective study of case records of patients presenting to the Edinburgh poisons treatment unit over 3 years (2000-2002). Information--including that on stated dose ingested, ECG parameters, and pulse and blood pressure--was extracted from case notes.

RESULTS

A total of 224 chlorpromazine, 96 thioridazine and 99 patients ingesting other anti-psychotics were evaluated. Full data on all aspects, both dose and cardiovascular change, was available in 96 chlorpromazine, 36 thioridazine and 27 of the other anti-psychotic cases. For thioridazine, there was a significant dose-response relationship for increasing heart rate and increasing QTc but not other cardiovascular changes. For chlorpromazine, there was no dose-response relationship for ECG changes, but there was a significant dose-response relationship for increasing heart rate and reduction in mean blood pressure.

CONCLUSIONS

We have confirmed a relationship between increasing dose of thioridazine and prolongation of QTc in overdose patients. No such change was observed with chlorpromazine. Both of these agents are reported to cause QT prolongation, but this study suggests that the nature of these effects is different for each agent. Poisoned patients may offer ways of exploring in more detail, and at a larger dose range, the effects of potentially cardiotoxic drugs in humans.

Potential for drug interactions involving cytochromes P450 2D6 and 3A4 on general adult psychiatric and functional elderly psychiatric wards

AIMS

To assess the potential for interactions involving cytochromes P450 2D6 (CYP2D6) and 3A4 (CYP3A4) between drugs prescribed in a city in-patient psychiatric service.

METHODS

Prescription information was obtained from all 236 patients in general adult wards and all 87 patients in functional elderly wards under a city psychiatric service. The frequencies with which combinations of drugs expected to interact via CYP2D6 or CYP3A4 were documented and compared between these two settings.

RESULTS

All 2089 drug prescriptions, of which 1237 (59%) were administered, were analyzed. One hundred and seventy-two patients (73%) on adult wards and 59 (68%) on functional elderly wards were prescribed at least one drug metabolized by and/or inhibiting CYP2D6, the difference being nonsignificant (95% confidence interval on the difference -6.3%, 16.4%). Anticipated interactions from 62/82 CYP2D6-related combinations prescribed on adult wards (27/100 patients) and 19/30 prescribed to elderly patients (22/100 patients) were judged to be clinically important or potentially clinically important. The proportion of patients on functional elderly wards prescribed at least one drug interacting with CYP3A4 (87%) was significantly greater than that for patients on adult wards (57%, P < 0.001). The frequency of interactions involving CYP3A4 was significantly greater on functional elderly than adult wards (43/100 vs 22/100 patients, P < 0.025, 95% confidence interval on the difference 4, 38/100).

CONCLUSIONS

Our findings confirm extensive polypharmacy on general adult psychiatric and functional elderly psychiatric wards. A substantial proportion of patients were receiving combinations of drugs that interact with CYP2D6 and/or CYP3A4, many of which are known to produce clinically important interactions. Doctors practising in old age psychiatry should be aware that patients on functional elderly wards are at increased risk of clinically important CYP3A4 interactions. Psychiatrists should consider the pharmacokinetic implications of drugs prescribed for use 'as needed', because of the potential for unpredictable interactions.

Effects of licence change on prescribing and poisons enquiries for antipsychotic agents in England and Scotland

AIMS

To examine the effect of licence change for thioridazine at the end of 2000 on the prescription of antipsychotic drugs in England and Scotland, and investigate changes in poisons information inquiries and, for Edinburgh, poisons admissions.

METHODS

Prescription data for antipsychotic drugs were obtained for England and Scotland and quarterly trends examined for 2000 and 2001. Accesses to the UK National Poisons Information Service website TOXBASE for antipsychotic products were examined for the same period. For Scotland telephone enquiry data, and admission data to the Edinburgh Poisons Unit were also evaluated. Trends in poisonings were compared with prescribing change.

RESULTS

In England prescriptions for thioridazine fell rapidly in 2001 from approximately 35% of market share to less than 5%, and were replaced by risperidone, chlorpromazine and olanzapine. TOXBASE accesses fell from 39.3% of antipsychotics to 4.4%. Accesses for chlorpromazine, olanzapine and risperidone increased. In Scotland prescribing of thioridazine was similar to changes in England, but it was principally replaced by chlorpromazine. These changes were mirrored by TOXBASE accesses, telephone enquiries and in-patient admissions. The ratio of TOXBASE accesses for thioridazine to prescription numbers for the drug increased after the licence change.

CONCLUSIONS

Licence change produced rapid change in prescribing behaviour within 3 months. Prescribing behaviour in England and Scotland was different. Changes in prescribing were mirrored by changes in accesses for poisons information in both England and Scotland, and in Edinburgh by hospital admissions. The increase in the ratio of TOXBASE accesses to prescriptions for thioridazine suggests doctors may have become more aware of its potential toxicity.