Thioridazine dosage

THiORiDAZiNE Dosage must be individualized and the smallest effective dosage should be determined for each patient. 

J Clin Psychopharmacol 21 382—388, 2001 Hamilton JD Thioridazine retinopathy within the upper dosage limit. Psy-chosomatics 26 823-824, 1985... 

With the use of major tranquillisers, for example, thioridazine, chlorpromazine, or perphenazine, it is possible to withdraw opiate dependents who are highly motivated. The dosages can be titrated to the degree of clinical symptoms and this can be monitored with key carers through an out-patient clinic. The use of hypnotics should be restricted to short-term use due to their own dependency problems, but they can be a useful addition, particularly in the early phases of the treatment programme. 

Because of increased responsiveness to all these drugs, dosage should usually be started at a fraction of that used in young adults. The half-lives of some phenothiazines are increased in the geriatric population. Thioridazine s half-life, for example, is more than doubled. Plasma protein binding of fluphenazine is reduced, which results in an increase of the free drug total drug ratio. 

Fluvoxamine inhibits CYP1A2, and a low dosage (50 mg/ day) produced a 225% increase in plasma thioridazine concentrations in 10 patients with schizophrenia (31). This was not reflected in an increased incidence of clinical adverse events however, thioridazine prolongs the QTC interval, which was not measured. 

Acute toxic effects of thioridazine on the eyes include nyctalopia, blurred vision, and dyschromatopsia, which typically become evident after 2-8 weeks of dosages over 800 mg/day. 

It is now recognized that the primary clinical fector associated with thioridazine retinopathy is the daily dose of drug. Before becoming aware of the dose-related retinal toxicity, dosages exceeding 1,600 mg daily were commonly prescribed. Few cases of pigmentary retinopathy have been reported, however, with daily dosages of less than 800 mg. 

Pigmentary retinopathy, which can seriously impair vision, is specifically associated with thioridazine, and has occurred more often with high and prolonged dosage... 

I Sedation and Cognition. Sedation must be recognized as an antipsychotic side effect and not as an indication of therapeutic effect. It occurs more frequently with antipsychotics with antihistaminic properties. Chlorpromazine, thioridazine, mesoridazine, clozapine, olanzapine, and quetiapine are most frequently implicated. Administration of most or all of the daily dosage at bedtime (depending on the drug half-life) can decrease daytime sedation and in some patients eliminate the need for hypnotic agents. Sedation occurs early in treatment... 

KountourelHs, J.E. Markopoulou, C.K. A simultaneous analysis by hig i performance liquid chromatography of bamipine combined with tricyclic antidepressants and/or antipsychotics in dosage forms. J.Liq.Chromatogr., 1991,14, 2969-2977 [simultaneous heunipine, chlorprothixene, haloperidol, imip-ramine, prochlorperazine, thioridazine, trifluoperazine, trimeprazine, trimipramine]... 

In patients with schizophrenia or bipolar disorder given quetiapine 300 mg twice daily, thioridazine 200 mg twice daily reduced the steady-state quetiapine AUC and its maximum and minimum plasma levels by about 41%, 48% and 33%, respectively. It was suggested that this was due to an increased metabolism of quetiapine, although the mechanism for this effect was unclear. These reductions are only moderate and their importance is not known, but until more information is available it would seem prudent to monitor concurrent use, being alert for the need to raise the quetiapine dosage. 

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