Effects of tiapride in tardive dyskinesia

Drug-induced parkinsonism

INTRODUCTION

Drug-induced parkinsonism (DIP) is the second most common cause of parkinsonism after idiopathic Parkinson's disease (iPD). Initially reported as a complication of antipsychotics, it was later recognized as a common complication of antidepressants, calcium channel antagonists, gastrointestinal prokinetics, antiepileptic drugs and many other compounds. Despite being a major health problem in certain populations, it seems to be frequently overlooked by the medical community.

AREAS COVERED

This paper approaches the concept of DIP, reviews its epidemiology, clinical features and ancillary tests recommended for a correct diagnosis. The authors discuss the different drugs and its pathogenic mechanisms. The relevance of an early recognition and recommendations for a correct management are commented.

EXPERT OPINION

Prescribers need to remain vigilant for DIP, particularly in the elderly, patients taking multiple drugs and those with genetic risk factors involved in iPD. Cessation of the causing agent is the main treatment and there is no evidence of benefit for the use of anticholinergics or levodopa. If the medication cannot be withdrawn, it should be switched to agents with a lower risk of DIP.

Drug-induced parkinsonism

Drug-induced parkinsonism (DIP) is the second cause of akinetic rigid syndrome in the Western world and its prevalence is increasing and approaching that of idiopathic Parkinson's disease due to the ageing of the population and to the rising of polypharmacotherapy. DIP was initially reported as a complication of neuroleptics in psychiatric patients, but it has also been described with a great diversity of compounds such as antiemetics, drugs used for the treatment of vertigo, antidepressants, calcium channel antagonists, antiarrythmics, antiepileptics, cholinomimetics and other drugs. Although traditionally considered reversible, DIP may persist after drug withdrawal. At least 10% of patients with DIP develop persistent and progressive parkinsonism in spite of the discontinuation of the causative drug. Irreversible or progressive DIP has been considered as an indication of presymptomatic parkinsonian deficit, unmasked but not caused by the offending drug, but it could be explained by persistent toxicity of the responsible pharmacological agents on the nigrostriatal dopamine pathway. The best treatment of DIP is prevention, including the avoidance of prescription of causative drugs whenever it is not strictly necessary. In patients who require potentially risky medication, it is necessary to perform adequate monitoring for early parkinsonian deficits and early discontinuation if these deficits appear. Atypical neuroleptics are associated with lower risk than first generation antipsychotic drugs. Special precautions are needed in elderly subjects, in patients treated with multiple drugs for prolonged periods of time and in those with familial risk factors including familial parkinsonism or tremor, or in those with genetic variants of genes involved in idiopathic Parkinson's disease.

Drug-induced parkinsonism: a review

The main clinical features, pathophysiology and underlying mechanisms of drug-induced parkinsonism are reviewed. The clinical manifestations of drug-induced parkinsonism are often indistinguishable from idiopathic Parkinson's disease. However, some subtle differences may exist: for example drug-induced parkinsonism is often associated with tardive dyskinesias, bilateral symptoms and the absence of resting tremor, etc. Besides toxins (eg manganese, carbon monoxide or MPTP), many drugs are known to produce parkinsonism: dopamine blocking drugs (true neuroleptics used as antipsychotics: phenothiazines, butyrophenones, thioxanthenes but also sulpiride, "hidden" neuroleptics prescribed as anti-nausea or anti-vomiting drugs (such as metoclopramide and other benzamide derivatives), dopamine depleting drugs (reserpine, tetrabenazine), alpha-methyldopa, calcium channel blockers (flunarizine, cinnarizine, etc). The putative role of other drugs (eg fluoxetine, lithium, amiodarone) as well as the therapeutic management of this side effect are reviewed.

Zuclopenthixol, a combined dopamine D1/D2 antagonist, versus haloperidol, a dopamine D2 antagonist, in tardive dyskinesia

Animal data suggest that a D1 antagonistic component in neuroleptic drugs counteracts development of dopamine supersensitivity and of tolerance to cataleptic effect. This has led to the hypothesis that neuroleptics with D1 antagonistic activity should cause a better suppression of tardive dyskinesia (TD) and less rebound aggravation after withdrawal than pure D2 antagonists. In this study the effect of zuclopenthixol (mixed D1/D2 antagonist) and haloperidol (D2 antagonist) was evaluated in chronic psychotic patients with TD. Fifteen patients completed a randomized crossover study with blind evaluation of TD and parkinsonism. The test medications, haloperidol and zuclopenthixol, caused a significant suppression of TD and a significant increase of parkinsonism. No significant differences between haloperidol and zuclopenthixol were observed. No TD aggravation was seen. The lack of differences between the mixed D1/D2 antagonist and a D2 antagonist suggest that tolerance and DA supersensitivity play no or a minor role for development of TD.

Clinical and biochemical effects of gamma-vinyl Gaba in tardive dyskinesia

Clinical and biochemical effects of Gamma-vinyl-Gaba (GVG) have been evaluated in a blind video-controlled study in 10 psychiatric patients (mean age 71 yr) with tardive dyskinesia. CSF free and total Gaba and homocarnosine concentrations increased from three to five fold with GVG treatment. Despite the GVG-induced biological effects on Gaba metabolism, GVG did not consistently improve tardive dyskinesia. Psychomotor side-effects occurred in older patients, who only tolerated GVG dosages of 2-4 g/day.

Assessment of the therapeutic range of tiapride in patients with tardive dyskinesia

Ten patients with tardive dyskinesia were treated with tiapride at an increasing dosage to establish the dose-concentration relationship and the dose-effect relationship. The effect was scored with the Abnormal Involuntary Movement Scale (AIMS) and the Doppler-radar method. The intra individual dosage-serum concentration correlation coefficients varied from 0.86 to 0.99 and the slopes of the individual regression lines varied from 0.16 to 0.58. All patients showed a diminution of their involuntary movements during the treatment period. A negative correlation coefficient was found between the dosage of tiapride and the AIMS; range -0.22 till -0.93, mean: -0.65 +/- 0.23 (SD). The Doppler-radar method results were inconclusive. No side-effects were observed.

Pharmacokinetics of tiapride in patients with tardive dyskinesia and Huntington's disease

The pharmacokinetics of tiapride were determined at steady-state in 5 patients with tardive dyskinesia and 2 patients with Huntington's disease given tiapride 100 mg t.i.d. for 7 days. The maximum serum concentration of tiapride of 1.47 +/- 0.35 micrograms/ml was reached after 1.4 +/- 0.67 h. The half-life time of elimination was 229 +/- 41 min. About 50% of the dose of tiapride was excreted unchanged by the kidney. Neither protein binding nor glucuronide, sulphate or acetyl conjugation was observed. Renal clearance in the patients appeared to be lower but the other pharmacokinetic parameters did not differ from previous findings in healthy young volunteers.