Plasma levels of the enantiomers of thioridazine, thioridazine 2-sulfoxide, thioridazine 2-sulfone, and thioridazine 5-sulfoxide in poor and extensive metabolizers of dextromethorphan and mephenytoin.

Concentrations of total (R) + (S) and of the enantiomers (R) and (S) of thioridazine and metabolites were measured in 21 patients who were receiving 100 mg thioridazine for 14 days and who were comedicated with moclobemide (450 mg/day). Two patients were poor metabolizers of dextromethorphan and one was a poor metabolizer of mephenytoin. Cytochrome P450IID6 (CYP2D6) is involved in the formation of thioridazine 2-sulfoxide (2-SO) from thioridazine and also probably partially in the formation of thioridazine 5-sulfoxide (5-SO), but not in the formation of thioridazine 2-sulfone (2-SO2) from thioridazine 2-SO. Significant correlations between the mephenytoin enantiomeric ratio and concentrations of thioridazine and metabolites suggest that cytochrome P450IIC19 could contribute to the biotransformation of thioridazine into yet-unknown metabolites, other than thioridazine 2-SO, thioridazine 2-SO2, or thioridazine 5-SO. An enantioselectivity and a large interindividual variability in the metabolism of thioridazine have been shown: measured (R)/(S) ratios of thioridazine, thioridazine 2-SO fast eluting (FE), thioridazine 2-SO slow eluting (SE), thioridazine 2-SO (FE+SE), thioridazine 2-SO2, thioridazine 5-SO(FE), and thioridazine 5-SO(SE) were (mean +/- SD) 3.48 +/- 0 .93 (range, 2.30 to 5.80), 0.45 +/- 0.22 (range, 0.21 to 1.20), 2.27 +/- 8.1 (range, 6.1 to 40.1), 4.64 +/- 0.68 (range, 2.85 to 5.70), 3.26 +/- 0.58 (range, 2.30 to 4.30), 0.049 +/- 0.019 (range, (0.021 to 0.087), and 67.2 +/- 66.2 (range, 16.8 to 248), respectively. CYP2D6 is apparently involved in the formation of (S)-thioridazine 2-SO(FE), (R)-thioridazine 2-SO(SE), and also probably (S)-thioridazine 5-SO(FE) and (R)-thioridazine 5-SO(SE).

Determination of the enantiomers of thioridazine, thioridazine 2-sulfone, and of the isomeric pairs of thioridazine 2-sulfoxide and thioridazine 5-sulfoxide in human plasma.

Thioridazine is a commonly prescribed phenothiazine drug administered as a racemate and it is believed that its antipsychotic effect is mainly associated with (R)-thioridazine. A method based on high-performance liquid chromatography has been developed for the determination of the enantiomers of thioridazine and thioridazine 2-sulfone (THD 2-SO2 or sulforidazine) and of the enantiomers of the diastereoisomeric pairs of thioridazine 2-sulfoxide (THD 2-SO or mesoridazine) and thioridazine 5-sulfoxide (THD 5-SO) in the plasma of thioridazine-treated patients. The method involves sequential achiral and chiral HPLC. The limits of quantitation for total (R) + (S) concentrations were found to be 15 ng/ml for thioridazine and 5 ng/ml for its metabolites. The limits for the determination of the (R)/(S) ratios were found to be 60 ng/ml for racemic THD and 10 ng/ml for racemic THD 2-SO, THD 2-SO2, THD 5-SO (FE) and THD 5-SO (SE). The method has been used to determine the concentrations of the enantiomers of thioridazine and of its metabolites in the plasma of a patient treated with 100 mg of racemic thioridazine hydrochloride per os per day for 14 days. The results show a high enantioselectivity in the metabolism of this drug: the (R)/(S) ratios for THD, THD 2-SO (FE), THD 2-SO (SE), THD 2-SO2, THD 5-SO (FE) and THD 5-SO (SE) were found to be 3.90, 1.22, 6.10, 4.10, 0.09 and 28.0, respectively.

Determination of trimipramine and its demethylated and hydroxylated metabolites in plasma by gas chromatography-mass spectrometry.

A gas chromatographic-mass spectrometric (GC-MS) method has been developed, for the determination of trimipramine (TRI), desmethyltrimipramine (DTRI), didesmethyltrimipramine (DDTRI), 2-hydroxytrimipramine (2-OH-TRI) and 2-hydroxydesmethyltrimipramine (2-OH-DTRI). The method includes two derivatization steps with trifluoroacetic acid anhydride and N-methyl-N-(tert.-butyldimethyl silyl)trifluoroacetamide and the use of an SE-54 capillary silica column. The limits of quantitation were found to be 2 ng/ml for DTRI and 4 ng/ml for all other substances. Besides, methods have been optimized for the hydrolysis of the glucuronic acid conjugated metabolites. This specific detection method is useful, as polymedication is a usual practice in clinical situations, and its sensitivity allows its use for single-dose pharmacokinetic studies.

Artifacts in the analysis of thioridazine and other neuroleptics.

Although the sensitivity to light of thioridazine and its metabolites has been described, the problem does not seem to be widely acknowledged. Indeed, a survey of the literature shows that assays of these compounds under light-protected conditions have been performed only in a few of the numerous analytical studies on this drug. In the present study, thioridazine, its metabolites, and 18 other neuroleptics were tested for their sensitivity to light under conditions used for their analysis. The results show that light significantly affects the analysis of thioridazine and its metabolites. It readily causes the racemization of the isomeric pairs of thioridazine 5-sulphoxide and greatly decreases the concentration of thioridazine. This sensitivity to light varied with the medium used (most sensitive in acidic media) and also with the molecule (in order of decreasing sensitivity: thioridazine > mesoridazine > sulforidazine). Degradation in neutral or basic media was slow, with the exception of mesoridazine in a neutral medium. Twelve other phenothiazines tested, as well as chlorprotixene, a thioxanthene drug, were found to be sensitive to light in acidic media, whereas flupenthixol and zuclopenthixol (two thioxanthenes), clozapine, fluperlapine, and haloperidol (a butyrophenone) did not seem to be affected. In addition to being sensitive to light, some compounds may be readily oxidized by peroxide-containing solvents.

Plasma levels of trimipramine and metabolites in four patients: determination of the enantiomer concentrations of the hydroxy metabolites.

A two-step high-performance liquid chromatography method is described, using a CN column and an alpha 1-acid glycoprotein column, which allows the measurement of the enantiomers of the hydroxy metabolites of trimipramine in plasma of trimipramine-treated patients. Of the four patients analyzed, three showed approximately equimolar concentrations of the (D)- and (L)-enantiomers of the hydroxy metabolites (2-hydroxy-trimipramine and 2-hydroxy desmethyltrimipramine), and one was found to have roughly twice as much of the (L)-form and of the (D)-form of 2-hydroxy trimipramine and 2-hydroxy desmethyltrimipramine. From the data available on the pharmacological effects of the enantiomers of trimipramine, it is postulated that this interindividual variability in its pharmacokinetics is another factor that could contribute to the interindividual variability in its pharmacodynamics.

Dextromethorphan and mephenytoin phenotyping of patients treated with thioridazine or amitriptyline.

The metabolism of most tricyclic antidepressants and some phenothiazine neuroleptics is under the genetic control of hepatic cytochrome P-450IID6, which also regulates the metabolism of dextromethorphan. This study investigated the effect of treatment with amitriptyline or thioridazine on testing for genetically regulated efficiency of the metabolism of dextromethorphan and mephenytoin. One group of 33 patients was treated with 150 mg amitriptyline a day (the AMI group); 25 other patients received a daily dose of thioridazine, either 200 mg (200-THD group; n = 7) or 400 mg (400-THD group; n = 18). Before and after 10 days of this treatment, all patients were tested with 25 mg dextromethorphan and 100 mg mephenytoin to determine their pharmacogenetic status with respect to their hepatic drug oxidizing systems (cytochrome P-450IID6 and P-450 MP). Two patients were poor metabolizers (PMs) of dextromethorphan and three of mephenytoin. Treatment with either psychotropic drug was without significant effect on the metabolism of mephenytoin, but both amitriptyline and thioridazine increased significantly the metabolic ratio of dextromethorphan/dextrorphan. Thioridazine had the effect of changing the pharmacogenetic status of 15 efficient metabolizers of dextromethorphan to poor metabolizers; amitriptyline did not have such an effect. There was no significant correlation between day-11 plasma levels of thioridazine, mesoridazine, or sulforidazine and the metabolism of dextromethorphan, but there was a correlation between the metabolism of dextromethorphan and plasma levels of amitriptyline and nortriptyline. Amitriptyline (p less than 0.05), but not thioridazine, decreases the ratio of conjugated/total dextrorphan in urine.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of quinidine on the pharmacokinetics of trimipramine and on its effect on the waking EEG of healthy volunteers. A pilot study on two subjects.

The pharmacokinetics and pharmacodynamics (waking EEG) of 75 mg trimipramine taken orally were determined in two healthy volunteers on two separate occasions, once without and once after comedication with 2 x 50 mg quinidine. Quinidine, a potent cytochrome P-450IID6 inhibitor, is used as a pharmacological tool to mimic a lack of this enzyme in man. In this study, it markedly altered the pharmacokinetics of trimipramine, almost doubling its plasma half-life and decreasing its apparent clearance and volume of distribution. These results strongly suggest that trimipramine is a substrate of cytochrome P-450IID6. These modifications of trimipramine metabolism were accompanied by measurable changes in some EEG variables, most notably with regard to the relative power in the alpha and theta bands, which showed higher and longer-lasting effects of trimipramine. Since cytochrome P-450IID6 is deficient in 5-10% of Caucasian subjects, this may have consequences in trimipramine-treated subjects, especially with regard to the effects of the drug on the EEG.

Light-induced racemization: artifacts in the analysis of the diastereoisomeric pairs of thioridazine 5-sulfoxide in the plasma and urine of patients treated with thioridazine.

The ring sulfoxidation of thioridazine (THD), a widely used neuroleptic agent, yields two diastereoisomeric pairs, fast- and slow-eluting (FE and SE) thioridazine 5-sulfoxide (THD 5-SO). Until now, studies in which concentrations of these metabolites were measured in THD-treated patients have revealed no significant differences in their concentrations. Preliminary experiments in our laboratory had shown that sunlight and, to a lesser extent, dim daylight led to racemization and probably also to photolysis of the diastereoisomeric pairs as measured by high-performance liquid chromatography. Similar results were also obtained with direct UV light (UV lamp). In appropriate light-protected conditions, THD, northioridazine, mesoridazine, sulforidazine, and FE and SE THD 5-SO were measured in 11 patients treated with various doses of THD for at least 1 week. Significantly higher concentrations of the FE stereoisomeric pair were found. The concentration ratios THD 5-SO (FE)/THD 5-SO (SE) ranged from 0.89 to 1.75 in plasma and from 1.15 to 2.05 in urine. Because it is known that the ring sulfoxide contributes to the cardiotoxicity of the drug even more potently than the parent compound does, these results justify further studies to determine whether there is stereoselectivity in the cardiotoxicity of THD 5-SO.

[Treatment of depression by a combination of clomipramine and triiodothyronine]. / Traitement de la dépression par l'association de la clomipramine et de la triiodothyronine (LT3).

The clinical efficacy of a treatment with clomipramine (150 mg/day) associated with a daily dose of 50 micrograms of LT3 (CMI + LT3) compared to a treatment with clomipramine (150 mg/day) (CMI + placebo) for a period of 42 days has been examined in a pilot study, randomized in double-blind conditions, including 20 patients with a normal thyroid status, but presenting a major depressive syndrome (DSM III). The minimum including score was 30 on the Montgomery Asberg Scale (MADRS). The patients were considered as remitted when the MADRS-score was < or = 10. After 28 days of treatment, the efficacy of CMI + LT3 was found to be superior to CMI + placebo (p < 0.05). Side effects (CHESS 84) were those generally described for tricyclic antidepressants (constipation, dry mouth, lipothymia, tremor). Patients of the CMI + LT3 group experienced a slight hyperthyroidism. The determination of the plasma levels of CMI and desmethylclomipramine (DCMI) showed the presence of three non-compliant patients, but also that there was no relationship between plasma levels and clinical efficacy of the drug. Significant correlations were found between CMI and DCMI levels on day 14 compared with those of day 28 and 42, respectively. LT3 was without effect on the plasma levels of CMI and DCMI.

Acetylation of maprotiline and desmethylmaprotiline in depressive patients phenotyped with sulfamidine, debrisoquine, and mephenytoin.

A gas chromatographic/mass spectrometric method (using either electron impact or chemical ionisation with methane or ammonia) is described for the quantitative analysis of maprotiline (MP, Ludiomil), N-acetylmaprotiline (AcMP) and N-acetyldesmethylmaprotiline (AcDMP) in whole blood or plasma. In two groups (A and B) of 82 and 53 depressive patients treated clinically with MP for 10 and 21 days, respectively, plasma and whole blood MP was monitored during the treatment. In group A, all subjects were phenotyped with debrisoquine and mephenytoin, and 44 with sulfamidine. 5 patients were poor metabolizers of debrisoquine and 2 of mephenytoin; 18 subjects were fast acetylators of sulfamidine. Traces of AcMP were found only in two patients. AcDMP was present in levels below 2 ng/ml in the plasma of most of the patients in group A. In group B, AcDMP levels between 2.4-14.6 ng/ml of whole blood were found in 9 patients. The mass spectral data suggest the presence of another, unknown MP metabolite interfering partly with the analysis of AcDMP. The presence of AcDMP seemed not to be related to the phenotype of the patients as determined by the pharmacogenetic tests.

Amitriptyline pharmacokinetics and clinical response: II. Metabolic polymorphism assessed by hydroxylation of debrisoquine and mephenytoin.

A subgroup of 16 out of 30 endogenous depressive inpatients (cf. part I), treated for 3 weeks with 150 mg amitriptyline (AT) daily, participated in a pharmacogenetic study: all were phenotyped with debrisoquine and 3 of them with mephenytoin. Four patients were found to be poor metabolizers (PMs) of debrisoquine and one of mephenytoin. Plasma levels of AT + NT (nortriptyline) were highest in the PMs of debrisoquine, but the ratio of hydroxylated metabolites to the parent compounds appeared to be lower in these subjects. From these data, it is speculated that, in the PM of mephenytoin, the demethylation of AT is impaired. In 12 patients, free plasma 10-hydroxy-AT (ATOH) and 10-hydroxy-NT (NTOH) were found to be bound to a similar extent to plasma proteins, but not so firmly as their parent compounds, by a factor of 6 and 4 respectively. While mean total plasma ATOH reached only 15% of the value of AT, total plasma NTOH was as high as NT. ATOH correlated significantly with its parent compound, but NTOH did not correlate with NT. No drug plasma levels/clinical relationship was found in this small group of patients, even when the hydroxylated metabolites were taken into account. Both poor and extensive metabolizers of debrisoquine responded to treatment. The debrisoquine-test appears to be a useful clinical tool for detecting in patients a genetic deficiency in the hydroxylation of AT-type drugs.

Amitriptyline pharmacokinetics and clinical response: I. Free and total plasma amitriptyline and nortriptyline.

A group of 30 patients suffering from endogenous depression was treated with 150 mg amitriptyline (AT) for 21 days. Depression ratings and determinations of total and free plasma AT and nortriptyline (NT) were performed weekly. No correlation between clinical improvement and any of the biochemical parameters was found. Thus, this study does not support the existence of a therapeutic window for AT. A highly significant correlation was calculated between free and total AT and free and total NT, and also between the free fractions of AT and NT; moreover, age correlated significantly and positively with total plasma AT, but not with NT, and negatively with the free fractions of both AT and NT. The absence of correlation between clinical improvement and pharmacokinetic parameters is discussed for its possible significance. The finding that responders are also found in patients with "low" levels of antidepressants (corroborating the pharmacokinetic and pharmacodynamic data obtained in animals submitted to a long-term treatment with antidepressants) suggests that the concept of the need for steady-state levels with low fluctuations should be re-examined. In the light of these results the clinical effectiveness of treatment with higher drug doses, administered at larger intervals, in order to produce high amplitude fluctuations of the antidepressant should be studied.

[The use of low-dose amitriptyline in psychogeriatrics. A clinical, pharmacokinetic and pharmacogenetic study]. / Utilisation de l'amitriptyline à faible dose en psychogériatrie. Une étude clinique, pharmacocinétique et pharmacogénétique.

Two groups of six depressive psychogeriatric patients (age 69-93) have been treated for three weeks with either 25 mg or 50 mg of amitriptyline (AT) per day. Before the beginning of the treatment and after 8, 15 and 22 days of medication, the patients (7 outpatients and 5 hospitalized patients) underwent various psychopathological tests (Hamilton, Crichton) and biochemical investigations, i.e. clinical chemistry and hematology, analyses of AT and nortriptyline (NT), in the plasma. In some subjects the hydroxylated metabolites and the binding of these substances to plasma proteins were also measured. Except one patient, all responded favourably to the treatment. No difference between the two doses has been observed as regards their clinical efficacy and incidence of side effects. The plasma levels of AT and NT were below those generally recommended in the literature. The monitoring served to identify some cases of noncompliance and, in one patient, a deficiency of hydroxylation of AT, confirmed by the debrisoquine test. These results suggest that the "therapeutic window" needs redefinition and that low-dose medication with antidepressants is indicated in a psychogeriatric population.

Determination of compliance with riboflavin in an antidepressive therapy.

In a comprehensive study on the fate of amitriptyline (At, Laroxyl) in depressive patients, it was investigated whether their compliance could be controlled in analysing the concentration of riboflavin (vitamin B2) in urine. Therefore, they were medicated for 3 weeks with special tablets (Ro 4-1575/063) containing 150 mg At and 15 mg riboflavin. Different modalities or urine samplings were designed in order to establish the optimal conditions for testing compliance. Riboflavin, creatinine, At and nortriptyline were measured in urine, the tricyclic drugs also in plasma. The results show that compliance could be tested in analysing urine before and 4 h after the intake of the drug. However, this design was associated with a considerable subjective constraint for the patient.

On the relationship between free plasma and saliva amitriptyline and nortriptyline.

Conflicting results on the correlation of tricyclic levels in plasma and saliva have raised doubts about the clinical usefulness of monitoring these drugs in the latter body fluid. However, saliva drug levels may reflect the free plasma concentration, which possibly determines its level in the brain. In two groups of depressive patients, the evolution was studied of the levels of amitriptyline and nortriptyline in plasma (as free and total) and in saliva, after the administration of amitriptyline. The results show a poor correlation between total plasma and saliva concentration of amitriptyline and nortriptyline, respectively. Levels of both tricyclics in saliva exceed by far those measured in plasma dialysate. However, the relationship is such that free plasma concentrations may be predicted from those measured in saliva, if one takes into account saliva pH at the moment of collecting the sample.