Simplified method for monitoring tricyclic antidepressant therapy using gas--liquid chromatography with nitrogen detection

Capillary electrophoresis for the analysis of antidepressant drugs: A review

Depression is a common mental disorder that may lead to major mental health problems, and antidepressant drugs have been used as a treatment of choice to mitigate symptoms of major depressive disorders by ameliorating the chemical imbalances of neurotransmitters in brain. Since abusing antidepressant drugs such as selective serotonin reuptake inhibitors and tricyclic antidepressant drugs can cause severe adverse effects, continuous toxicological monitoring of the parent compounds as well as their metabolites using numerous analytical methods appears pertinent. Among them, capillary electrophoresis has been popularly utilized since the method has a lot of advantages viz. using small amounts of sample and solvents, ease of operation, and rapid analysis. This review paper brings a survey of more than 30 papers on capillary electrophoresis of antidepressant drugs published approximately from 1999 until 2018. It focuses on the reported capillary electrophoresis techniques and their applications and challenges for determining antidepressant drugs and their metabolites. It is organized according to the commonly used capillary zone electrophoresis method, followed by non-aqueous capillary electrophoresis and micellar electrokinetic chromatography, with details on breakthrough findings. Where available, information is given about the background electrolyte used, detector utilized, and sensitivity obtained.

The role of plasma level monitoring of tricyclic antidepressant drugs as an aid to treatment

Use of the tricyclic antidepressant drugs is the most common pharmacotherapeutic approach to the treatment of depression. It is a common clinical experience to find that a fair proportion of patients fail to show a satisfactory response and that others complain of side-effects. Important factors which influence this situation are the diagnostic criteria used to select patients for drug treatment, the dosage prescribed and individual compliance. Measurement of plasma drug concentrations has been proposed as a more rational way of increasing the efficacy of antidepressant medication and avoiding toxicity. A number of studies have shown a correlation between plasma concentrations of these drugs and clinical effects, but the relationship is far from simple. With amitriptyline and nortriptyline there is good evidence for a 'therapeutic window' within which maximum antidepressant action is obtained. Many patients being treated with these drugs have plasma levels outside recommended therapeutic ranges. Experience in our department has shown that there are a number of clinical situations where routine plasma level monitoring of selected antidepressants is of value: (1) inadequate clinical response; (2) side-effects/toxicity; (3) complicating medical conditions; (4) suspected poor compliance; and (5) long-term therapy. Such measurements are a relatively simple and inexpensive way of maximizing the benefits of drug therapy and a means of tailoring drug dosages to suit individual requirements.

Psychotropic drugs in mothers' milk: a comprehensive review of assay methods, pharmacokinetics and of safety of breast-feeding

Many mentally ill women want to breast-feed their babies but, if they are taking psychotropic drugs, there is very little systematic data upon which to base decisions about whether or not it is safe to do so. We therefore attempt to provide a comprehensive and critical summary of existing case reports and of studies of breast-feeding in relation to commonly used psychotropic drugs. The literature review focuses on the following drugs: antidepressants: tricyclics and serotonin selective reuptake inhibitors (SSRIs); antipsychotic drugs: chlorpromazine, perphenazine, haloperidol and clozapine; mood stabilizers: lithium and carbamazepine; and benzodiazepines. The research literature consists mainly of single case reports and there have been very few attempts at controlled, longitudinal investigations. Findings are often difficult to compare because of differences in methods or because of lack of key information. Most data are available about the tricyclic antidepressants but even here we have found that the reports cover only a grand total of 66 mother-infant pairs. Dilemmas about whether or not to contraindicate breast-feeding arise most commonly in relation to postnatal depression. The findings to date suggest that provided that infants are healthy at the outset it is likely that the benefits of breast-feeding will outweigh potential hazards if their mothers are taking established tricyclic drugs at recommended dose levels. Much less is known about risks associated with SSRI antidepressants or about antipsychotic drugs such as phenothiazines and butyrophenones or mood stabilizers such as carbamazepine, all of which enter breast-milk. Safeguards are suggested for future single case studies, which, as they accumulate, will provide a platform for mounting controlled prospective studies properly to test for any acute toxic effects and for possible long-term adverse effects of such drugs on infants' development. Appendix 1 is a review of assay methods. Appendix 2 examines pharmacokinetic factors in newborn preterm and sick infants with special reference to contraindications to breast-feeding. Appendix 3 is a review of methods for assessing infant health and development.

Drug monitoring of clomipramine and desmethylclomipramine in depressed patients using a new liquid chromatographic assay

A method has been developed for the quantitative analysis of clomipramine and its major metabolite desmethylclomipramine in plasma, using normal phase chromatography with UV detection at 254 nm. This rapid (6 min) and highly sensitive methodology (detection limits 0.5 ng/mL and 2 ng/mL for clomipramine and desmethylclomipramine, respectively; S/N = 3, 0.001 aufs) allows pharmacokinetic studies and drug monitoring of the two compounds. Using the described methodology we report an application which involved 10 depressed inpatients.

Predicting severity of tricyclic antidepressant overdose

The measurement of plasma concentration, a prolonged QRS interval, and level of consciousness have all been recommended as useful indicators of toxicity following tricyclic antidepressant overdose. The aims of this study were firstly, to determine the relative prognostic value of each of these indicators and secondly, to assess when a patient can be discharged safely from the intensive care unit. Data were evaluated on 67 patients with tricyclic antidepressant overdose from four centers. Plasma tricyclic antidepressant concentrations were measured, coma grade was evaluated using the Matthew-Lawson Coma Scale and a ECG was obtained from 23 patients on admission. Complications such as convulsions, hypotension, arrhythmias, and need for intubation and ventilation were recorded. Thirty patients developed complications and no patient died. Coma grade was the best predictor of outcome. The development of serious complications is unlikely in patients whose level of consciousness is grade II or less and who are admitted to hospital more than 6 h after overdose. Plasma tricyclic antidepressant concentration was of no additional value in predicting toxic complications or deciding when the patient could leave the intensive care unit. Our study suggests that an alert and orientated patient with a QRS duration less than 100 ms is the best indicator for safe transfer to a medical or psychiatric ward.

Effects of clomipramine treatment on cerebrospinal fluid monoamine metabolites and platelet 3H-imipramine binding and serotonin uptake and concentration in major depressive disorder

In an open study of 12 inpatients who met the DSM-III criteria for a major depressive episode, the effects of clomipramine (CI) on the monoamine metabolites 5-hydroxyindoleacetic acid (5-HIAA), homovanillic acid (HVA), 4-hydroxy-3-methoxyphenyl glycol (HMPG) in cerebrospinal fluid (CSF) were measured simultaneously with the effects on 3H-imipramine binding, serotonin (5-HT) uptake and 5-HT concentration in platelets after 3 and 6 weeks of treatment. Drug (CI and desmethylclomipramine) plasma concentrations were determined. The concentrations of 5-HIAA and HMPG decreased substantially, and the concentration of HVA remained unchanged. There was also a large and significant reduction of the number of imipramine binding sites (Bmax) and of the platelet 5-HT concentration. The 5-HT uptake was not measurable after 3 weeks of treatment. None of the parameters changed significantly between weeks 3 and 6. There were no significant correlations between antidepressant effect (measured by the Montgomery-Asberg Depression Rating Scale) and plasma drug concentrations, although a tendency to a significant correlation between antidepressant effect and CI was observed at 3 weeks. There were no significant intercorrelations between the different 5-HT parameters and no other significant correlations between the biochemical measures and clinical outcome.

Comparative effects of the diastereoisomers, quinine and quinidine in producing phenocopy debrisoquine poor metabolisers (PMs) in healthy volunteers

1. A single oral dose (50 mg) of quinidine significantly increased the debrisoquine metabolic ratio in six healthy volunteers. For four of the volunteers the metabolic ratio changed to that typical of the poor metaboliser (PM) phenotype. 2. The effect of quinidine in producing debrisoquine oxidation "poor metaboliser" phenocopies persisted for at least 3 days but had disappeared by 1 week. 3. The debrisoquine metabolic ratios for the same six subjects were not significantly altered by the oral administration of quinine (200 or 400 mg), the diastereoisomer of quinidine. 4. The plasma pharmacokinetic parameters of both nortriptyline and desipramine in healthy volunteers were all changed to those more typical of the debrisoquine PM phenotype following the concomitant administration of quinidine (50 mg). 5. It is concluded that quinidine, but not its diastereoisomer quinine, is a potent selective inhibitor of the in vivo oxidation of debrisoquine and can produce an artifactual PM phenocopy in persons who are phenotypically extensive metaboliser (EM) phenotype status. The clinical implications of this observation are discussed.

A comparative clinical trial of fluoxetine, mianserin and placebo in depressed outpatients

Fluoxetine, a selective serotonin reuptake inhibitor, was compared with mianserin and placebo in a double-blind study. In total, 81 depressed patients were included. Patients were rated weekly on the Hamilton Depression Rating Scale (HDRS) and the Montgomery & Asberg Depression Rating Scale (MADRS). The duration was 6 weeks, and 52 patients completed the study. Significantly more patients on fluoxetine improved than patients on placebo. For mianserin no significant differences were found with either fluoxetine or placebo. Mean HDRS at the end of the study was also statistically significantly lower for fluoxetine, but not for mianserin, than placebo. Subscores of the MADRS showed improved sleep on mianserin at weeks 2 and 3. Suicidal feelings were reduced to a greater degree on fluoxetine than on mianserin and placebo at weeks 6 and 7. Fluoxetine induced weight loss, while patients on mianserin gained weight. Side effects were present in most patients on the two active drugs; those on fluoxetine experienced nausea and vomiting, and those on mianserin drowsiness.

Clomipramine in obsessive-compulsive ritualisers treated with exposure therapy: relations between dose, plasma levels, outcome and side effects

Forty-nine obsessive-compulsive ritualisers completed a double-blind controlled study of clomipramine and exposure therapy. More severely ill patients allowed higher doses of medication to be prescribed and had higher plasma levels of both clomipramine and desmethylclomipramine. Exposure instructions had a strong effect, whereas the clomipramine effect was small and short-lived. Plasma levels of desmethylclomipramine but not of clomipramine correlated with outcome at weeks 8 and 17. There was no evidence of a therapeutic window for either clomipramine or its metabolite. Patients' physical complaints before treatment correlated positively with depression and anxiety, especially sexual difficulties. Dry mouth, as a side effect, was most evidently related to clomipramine and its usefulness in monitoring drug compliance for patients on clomipramine is reaffirmed.

The effect of a lipid suspension on amitriptyline disposition

A 5-h infusion of a lipid suspension or saline was given on separate occasions to four healthy volunteers taking amitriptyline. Mean plasma levels of amitriptyline plus nortriptyline were 14% higher at the end of the lipid infusion but the difference was not statistically significant. Infusion of a lipid suspension is unlikely to materially affect the severity of amitriptyline intoxication.

Plasma concentrations of mianserin after single dose and at steady-state in depressed elderly patients

Plasma mianserin and desmethylmianserin concentrations were measured in 17 clinically depressed elderly patients after a single 30 mg dose of mianserin. The patients then received mianserin 30 mg daily for up to 6 weeks and the plasma concentrations were measured at weekly intervals. The relationship between concentrations of mianserin and desmethylmianserin at steady-state and at 16 and 24 hours after the single test dose was not good enough to be used for prediction of dosage requirements. Reasons for this finding are discussed.

A simplified radioimmunoassay of plasma nortriptyline in depressed patients compared with high-pressure liquid chromatography and gas-liquid chromatography

Antiserum to nortriptyline was generated in male New Zealand rabbits innoculated with n-succinylnortriptyline-bovine serum albumin conjugates. The antiserum was used at a final dilution of 1:4000 and tritiated imipramine was used as the label antigen. An accurate, sensitive, and specific radioimmunoassay of depressed patients' plasma or serum nortriptyline is described. The accuracy was good with a recovery range of 90-100% with a mean of 94%. The method can be used to measure nortriptyline concentration in the range of 0.1 microgram/liter to 100 micrograms/liter without prior extraction and purification of plasma or serum. Results of this method correlate well with those obtained by high-pressure liquid chromatography (r = 0.979) and by gas-liquid chromatography (r = 0.98). The specificity of the antiserum was examined by studying the cross-reactivity of 20 different psychopharmacological compounds, including nortriptyline's metabolites.

Hemodynamic and electrocardiographic effects of fluoxetine and its major metabolite, norfluoxetine, in anesthetized dogs

The cardiovascular effects of the selective serotonin uptake inhibitor, fluoxetine, and its N-desmethyl metabolite, norfluoxetine, were studied in anesthetized dogs during constant iv infusion of supratherapeutic doses (0.1 mg/kg/min for 50 min). Fluoxetine and norfluoxetine did not significantly affect mean blood pressure, pulmonary artery wedge pressure, or heart rate compared to a corresponding vehicle group. Cardiac output fell 15 to 20% during fluoxetine infusion due to nonsignificant decreases in both heart rate (10%) and stroke volume (5 to 10%). In contrast, the tricyclic antidepressant agent, amitriptyline, infused at the same dose, decreased both mean pressure and systemic vascular resistance (20%) and increased heart rate (20%). Pulmonary wedge pressure rose by 35%, and stroke volume fell by 20% suggesting impaired ventricular contractility. Both intramyocardial and infranodal conduction was slowed during amitriptyline infusion as indicated by increases in the QRS duration, and the PQ and HV interval. Fluoxetine and norfluoxetine had no influence on cardiac impulse conduction velocity as assessed by either surface or intracardiac conduction indices. Plasma concentrations of fluoxetine, norfluoxetine, and amitriptyline reached during infusion ranged from 1.0 to 2.5 micrograms/ml. Platelet [3H]serotonin uptake was inhibited by 95% during infusion of fluoxetine and about 75% during infusion of norfluoxetine or amitriptyline. These observations indicate that large iv doses of fluoxetine or norfluoxetine lack prominent cardiodepressant effects in dogs, suggesting a greater margin of safety for fluoxetine compared to tricyclic antidepressant drugs.

Peripheral adrenoceptors and serotonin receptors in depression. Changes associated with response to treatment with trazodone or amitriptyline

Changes in platelet and lymphocyte adrenoceptor densities, platelet serotonin uptake and aggregatory response to serotonin were assessed in a group of moderately depressed patients before and during treatment with either trazodone or amitriptyline. Platelet serotonin receptor activity and uptake were lower before the start of treatment in all patients than in those patients responding to treatment. The densities of alpha 2- and beta-adrenoceptors tended to be higher in the patients before treatment and returned to control values after effective therapy. There were no major differences in the biochemical changes between the patients treated with trazodone or amitriptyline. When the biochemical data was correlated with the clinical history of the patients, it was found that only endogenously depressed patients, and not those with non-endogenous depression, had a significantly reduced platelet serotonin uptake rate. In addition, female depressives had a slightly lower platelet 5-HT aggregatory response than males irrespective to the type of depression.

Analysis of tricyclic antidepressant drugs in plasma and serum by chromatographic techniques

A review of methods for the determination of tricyclic antidepressants in plasma or serum, based on the application of chromatographic techniques, is presented. A general discussion of the techniques in terms of their precision, accuracy, sensitivity and selectivity, with respect to parent drug and metabolites, is used to facilitate a comparison of methods. No one technique can be claimed as the method of choice for these drugs, although gas-liquid chromatography with nitrogen selective detection has some strong claims, viz. generally good sensitivity and reproducibility of assays and ready availability of equipment in most laboratories. The ultimate choice of a method for determining tricyclics will be determined more by the clinical application (routine monitoring versus pharmacokinetics) than by other factors.

Reliable routine method for the determination of antidepressant drugs in plasma by high-performance liquid chromatography

We describe a rapid and reliable method using high-performance liquid chromatography for the simultaneous measurement of plasma concentrations of currently prescribed antidepressants and their main metabolites (amitriptyline, nortriptyline, trans-10-hydroxy-nortriptyline, clomipramine, desmethylclomipramine, imipramine, desipramine, zimeldine, norzimeldine, doxepin, desmethyldoxepin, trimipramine and mianserin). The method involves a single extraction of plasma at pH 10.1 with hexane-acetonitrile (98:2), solvent transfer to and evaporation in a disposable glass tube and subsequent chromatography of the residue on a CN bonded-phase column using acetonitrile-methanol-phosphate buffer (pH 7.0) as mobile phase. Protriptyline is used as the internal standard. Calibration curves remain linear up to at least 200 micrograms/l, detection limits are 5 micrograms/l, absolute recoveries are over 92%, and precision (coefficient of variation) is 6.9%. Norzimeldine and 10-hydroxynortriptyline show lower recoveries, protriptyline and 10-hydroxynortriptyline higher detection limits. Adsorption to glassware and chemical decomposition during analysis are shown to be negligible. Psychoactive and other drugs frequently prescribed in combination with anti-depressants have been tested for their chromatographic properties under the same conditions.

Amitriptyline dosage prediction in elderly patients from plasma concentration at 24 hours after a single 100mg dose

Fifteen depressed elderly patients (14 female, 1 male; mean age 85 years) received a single oral dose of amitriptyline. The concentration of amitriptyline plus nortriptyline in a blood sample taken 24 hours later was used to predict by means of a nomogram the amitriptyline dosage required for each patient. Each dose was selected to produce steady-state amitriptyline plus nortriptyline concentrations close to 140 micrograms/L. The daily dosage ranged from 20 to 100mg (mean 62mg). Patients received the individually calculated dose each night, and weekly blood samples were obtained for drug analysis. At 2 weeks, mean amitriptyline plus nortriptyline concentrations were 118 +/- 21 micrograms/L. Eight of the patients were studied for a further 2 weeks and the mean amitriptyline plus nortriptyline concentration was then 111 +/- 19 micrograms/L. The dose prediction test is easy to use and ensures each patient receives an adequate but safer dose of amitriptyline than might otherwise be prescribed routinely.

A study of the effects of zimelidine on the pharmacokinetics and pharmacodynamics of temazepam in healthy volunteers

In this double-blind two-period crossover study, ten healthy volunteers received either 200 mg zimelidine each morning for 5 days, or placebo on the same schedule. On day 5 they received 20 mg temazepam 2 h after zimelidine or placebo. A battery of psychometric tests and subjective measurements was carried out on days 4 and 5. Blood samples were collected on day 5 for pharmacokinetic analysis of temazepam. All the measures of psychomotor performance showed the effects of temazepam, as did two of the subjective measures, the "alert/drowsy" and "steady/dizzy" visual analogue scales. No effect of zimelidine alone on performance or subjective state was seen. Zimelidine showed no discernible interaction with the effects of temazepam as assessed by subjective reports, by psychomotor tests, or by pharmacokinetic analysis.

A double blind comparison of the efficacy and safety of trazodone and imipramine in endogenous depression

In a 6-week double blind non-crossover study, trazodone and imipramine have been compared in the treatment of patients with severe endogenous depression. By random allocation, 13 patients entered each treatment group. The mean maintenance dosage of trazodone was 300 mg (range 200-350 mg) and of imipramine 160 mg (range 150-175 mg). Some evidence is presented to suggest that trazodone may have an earlier anxiolytic effect than imipramine by day 4 and a greater antidepressant effect by day 22 of treatment. Apart from the frequency of impaired visual accommodation being significantly greater in the imipramine group, there were no differences between the treatments with respect to side-effects. No abnormalities were found from laboratory investigations and ECG assessments.

The effects of acute and repeated administration of various antidepressant drugs on clonidine-induced hypoactivity in mice and rats

Small doses of clonidine produce hypoactivity in mice and rats, probably by stimulating pre-synaptic alpha 2-adrenoceptors in the brain. When mice were injected with desmethylimipramine (DMI, 5 mg/kg) before clonidine it attenuated the hypoactivity, while pretreatment with amitriptyline (5 mg/kg) or mianserin (5 mg/kg) potentiated this behaviour. In rats, desmethylimipramine (20 mg/kg) inhibited and mianserin (5 mg/kg) potentiated the clonidine-induced hypoactivity. Amitriptyline (20 mg/kg), however, had no effect on this behaviour in rats. Mice were also given repeated injections of these 3 antidepressant drugs (5 mg/kg twice daily for 14 days) and were tested with clonidine 12 and 60 hr after the final treatment. At 12 hr desmethylimipramine and amitriptyline both attenuated the hypoactivity responses while the reduction by mianserin was marginal (potency DMI greater than amitriptyline greater than mianserin). At 60 hr, however, amitriptyline and mianserin both decreased the clonidine-induced responses while the attenuation by desmethylimipramine was slight (potency amitriptyline congruent to mianserin greater than DMI). In rats, repeated injections of desmethylimipramine (20 mg/kg), administered twice daily for 14 days, attenuated the clonidine-induced hypoactivity 12 hr after the final treatment and this effect persisted for at least 72 hr. Furthermore, the degree of inhibition of the behavioural responses did not correlate with plasma concentrations of desmethylimipramine and persisted after disappearance of the drug from plasma. In conclusion, these data suggest that after repeated injection, desmethylimipramine, amitriptyline and mianserin all produce an adaptive decrease in the function of central alpha 2-adrenoceptors but the time course of this change differs with the individual antidepressant drug administered.

A double-blind comparison of zimelidine and desipramine in endogenous depression

Zimelidine, a specific 5HT uptake inhibitor (final dose 225 mg), and desipramine, mainly a noradrenaline uptake inhibitor (final dose 150 mg), were given in random order to 24 in- and out-patients fulfilling the Research Diagnostic Criteria for Major Depressive Disorder, definite or probable endogenous type, for a 3-week treatment period. Nonresponders were crossed over to the other drug for another 3 weeks. There was a nonsignificant trend towards more overall improvement on desipramine. Some patients in both groups showed very little change during 3 weeks, indicating a bimodal distribution of response to either drug. Several nonresponders improved markedly upon direct crossing over to the other drug. There were few and mild side effects on both drugs, with no significant difference between them. No significant correlation was found between improvement and plasma concentrations of zimelidine, norzimelidine, or desipramine, whereas a significant positive correlation was found between improvement and platelet serotonin uptake inhibition (measured in fresh platelets incubated in diluted plasma from the patients) in zimelidine-treated patients.

Relative acute cardiovascular toxicity induced by maprotiline, mianserin and nomifensine in conscious rabbits

The relative acute cardiovascular toxicity among three novel antidepressants: maprotiline, mianserin and nomifensine, has been assessed in conscious rabbits ip injected at 50 mg/kg, throughout a 150 min observation period. No death was observed in mianserin rabbits (n = 6), but 3 in the maprotiline rabbits (n = 8) and 1 death in the nomifensine group (n = 8), within the 2 hours. Cardiac output and renal blood flow were determined by the radioactive Sephadex microspheres method. Cardiac output values were significantly lowered (-29%) at 120 min only in mianserin rabbits, whereas renal blood flow values were reduced by 46.8% (mianserin, 35.8% (maprotiline) and 28% (nomifensine) at 120 min. In mianserin and maprotiline rabbits left ventricular pressure and mean arterial pressure fell significantly, but remained unchanged in nomifensine group. ECG disturbances consisting of ventricular and supraventricular extrasystoles were seen in all the injected rabbits, but QRS widening and right bundle branch block were solely observed after maprotiline and mianserin. Nomifensine rabbits experienced severe seizures with hypocapnia and metabolic acidosis. The drug myocardial/plasma ratio ranged between 59.3 (maprotiline) 13.25 (mianserin) and 0.92 (nomifensine). A rise in plasma catecholamines (epinephrine) was documented after mianserin but not after nomifensin and maprotiline. Nomifensine exhibited much lesser cardiotoxicity than mianserin and maprotiline at this dose (50 mg/kg), but induced more convulsions.

The demethylation of amitriptyline: a cross-over study of steady-state plasma levels of amitriptyline and nortriptyline in depressed patients

Five elderly depressed patients were treated with amitriptyline (AT) and nortriptyline (NT) in turn, in a cross-over design. Steady-state plasma drug levels were compared with those calculated for eight healthy subjects of previous single-dose studies. Plasma clearances were on average about 2.5 times lower in the patients than the healthy subjects, but the ratios of the different reaction rates did not differ significantly between the two groups. The interpretation of the ratio of NT levels during AT treatment and NT treatment, in terms of the fraction of AT that is metabolised by demethylation, is discussed. The ratio of NT level to AT level during AT treatment was particularly variable between individuals. This was apparently due to independent variation in (a) the ratio of plasma clearances of AT and NT and (b) the fraction of AT metabolised to NT.

Isocratic high-performance liquid chromatographic method for the determination of tricyclic antidepressants and metabolites in plasma

An isocratic high-performance liquid chromatographic method for the determination of six tricyclic antidepressants and their major metabolites is presented. Hexane containing 0.5% diethylamine was used as an extraction solvent to minimize adsorption onto glass. A reversed-phase cyanopropylsilane column was used with a mobile phase consisting of 70% acetonitrile and 30% 0.03 M acetate buffer, pH 7.0. Good identification and quantitation were obtained by the use of both UV detection at 245 nm and spectrofluorometric detection with an excitation wavelength of 276 nm and an emission filter with a 370-nm cutoff. A minimum detectable limit of less than 5 ng/ml of plasma is possible with this system. The reproducibility and precision of the method are shown from the analysis of samples containing 20-400 ng/ml in plasma.

Monitoring of tricyclic antidepressant therapy

During the three-year period 1978-1980, 2141 plasma samples from 1055 patients receiving therapy with amitriptyline (77%) or nortriptyline (23%) were analysed using GLC with nitrogen selective detection. Compared to the recommended therapeutic ranges, wild inter-individual differences were observed in plasma drug concentration, even when corrections for dosage were made. Concentrations ranged from below the limit of sensitivity of the assay (5 microgram.1(-1)) to greater than 1 mg.1(-1). The reporting of toxic symptoms subjective side-effects) was found not to reliably predict high drug concentrations. Serious complications, however, were associated with high plasma drug concentrations. Neither nortriptyline nor amitriptyline displayed dose-dependent pharmacokinetics over the concentration ranges studied. Treatment with either drug produced age-related increases in drug concentration, which were more pronounced in female patients. With amitriptyline therapy, there was an age-related decrease in the plasma nortriptyline:amitriptyline ratio, suggesting that demethylation may be more influenced by increasing age than hydroxylation. Plasma drug monitoring of tricyclic antidepressant therapy is the only reliable means of ensuring that all patients receive a fair opportunity to benefit from these drugs.

Nortriptyline therapy in elderly patients: dosage prediction from plasma concentration at 24 hours after a single 50 mg dose

Ten depressed elderly female patients in hospital (mean age 82 years) received a single oral dose of 50 mg nortriptyline prior to commencing treatment with this drug. The nortriptyline concentration in a plasma sample obtained 24 hours afterwards was used to predict the daily dose required to achieve a steady-state concentration within the range of 50-150 micrograms. l-1. The mean daily dose prescribed was 50 mg (range 20-100 mg). These dosage regimes provided a mean observed steady-state nortriptyline concentration of 104 micrograms. l-1, with a range of 76-180 microgram. l-1 (S.D. 30 microgram. l-1). Use of this prediction test can prevent the development of toxic plasma concentrations and enhance the possibility of therapeutic success.

A gas chromatographic method for the determination of antidepressant drugs in human serum

A universal gas chromatographic method for the determination of the most commonly used antidepressant drugs in 1 ml of serum is described. Prior to extraction the samples were washed with hexane at acid pH. After the hexane wash the drugs were extracted into hexane at pH approximately 10, and subsequently reextracted from the hexane into a 1% solution of formic acid in methanol. The methanolic phase was evaporated, the residue dissolved in isopropanol and analysed by gas chromatography with nitrogen detection on a 3% OV-225 column. Recoveries for amitriptyline, nortriptyline, clomipramine, desmethylclomipramine, doxepin, desmethyldoxepin, imipramine, desipramine, maprotiline, protriptyline, trimipramine and desmethyl-trimipramine were found to be 80% or higher. Limits of detection were found to be 5-10 ng/ml for teritary amines and 10-20 ng/ml for secondary amines. Interferences from some common basic drugs were investigated as well as interferences between different antidepressant drugs. Gas chromatographic data are given for 28 drugs and metabolites.

The pharmacokinetics of nortriptyline in patients with chronic renal failure

1 The pharmacokinetics of single oral doses of nortriptyline were studied in twenty patients with chronic renal failure, eight of whom were receiving treatment with haemodialysis. 2 The median nortriptyline half-life was 25.2 h (range 14.5-140.0 h) and the median nortriptyline clearance was 32.3 l/h (range 8.1-122.0 l/h). 3 No differences were observed between the dialysed and non-dialysed groups. 4 Comparisons of nortriptyline half-life and clearance between the patients and groups of physically healthy subjects revealed no significant differences. 5 There was no significant linear correlation between age and either of these measurements. In the twelve patients not receiving haemodialysis there was no correlation between nortriptyline clearance and glomerular filtration rate. 6 Chronic renal failure is not associated with a significant alteration in nortriptyline metabolism as measured by its half-life or clearance, but the drug should nonetheless be used with caution, and monitored whenever possible. However, the marked inter-individual differences observed in nortriptyline half-life and clearance in patients with chronic renal failure may not be solely responsible for their unpredictable response to tricyclic antidepressant therapy, and other possible contributory factors are discussed.

A double blind comparison of zimelidine and amitriptyline in endogenous depression

In a randomized double-blind group comparison study of 40 patients with endogenous depression zimelidine appeared to be as effective an antidepressant as amitriptyline at 4 and 6 weeks using the Hamilton Rating Scale (HRS) and the Montgomery and Asberg Depression Rating Scale (MADRS). At 2 weeks there was a significantly better response (P less than 0.05) on zimelidine compared to amitriptyline on the clinician's global scale and 4 out of 10 items on the MADRS suggesting an early onset of action. A significant better response to zimelidine was seen on the item somatic anxiety (HRS) while the effect on sleep and appetite was better in the amitriptyline group. There were significantly more side effects, raw and corrected, in the amitriptyline-treated group. High steady state plasma concentrations of norzimelidine (greater than 800 nmol/l) which were significantly correlated with age (r = 0.8) were associated with a significantly poorer response suggesting that a lower dose than 200 mg in older patients may be appropriate.

Amitriptyline pharmacokinetics. A crossover study with single doses of amitriptyline and nortriptyline

Six healthy volunteers were given single doses of amitriptyline (AT) and of nortriptyline (NT) separated by at least 10 days. Plasma concentrations of both compounds were measured at intervals for 48 or 72 h. The total areas under the concentration-time curves for the ingested drug were greater for NT, but AT concentrations showed much higher peak values and took more than 12 h to reach the terminal beta phase of elimination. Doses of 50 mg AT produced areas averaging slightly less than half those for 100 mg AT in the same subject, suggesting some saturation of the elimination process. The consumption of a large, fatty meal just before taking the AT tablets had little effect on the plasma drug concentration curves. NT half-lives, measured after ingestion of NT tablets, were used in analysing the production of NT from doses of AT in the same subject. There was a rapid early production, amounting to 30-67% of the total and presumably resulting from the first pass of AT through the liver. NT was then formed continuously at a rate always proportional to the simultaneous rate of AT elimination. The total amount of NT entering the systemic circulation was about one-quarter of the AT dose.

Effects of zimelidine and desipramine on serotonin and noradrenaline uptake mechanisms in relation to plasma concentrations and to therapeutic effects during treatment of depression

The selective inhibitors of neuronal 5-hydroxytryptamine (5-HT) and noradrenaline (NA) uptake, zimelidine and desipramine, were compared in a double blind crossover study of 40 inpatients with endogenous depression. The clinical effects of these two drugs and some biochemical variables related to the monoamine systems were studied during 4 weeks' treatment. Patients with a low pretreatment level of 5-hydroxyindoleacetic acid (5-HIAA) in the cerebrospinal fluid (CSF) (less than 20 ng/ml) responded significantly better to zimelidine treatment than those with a high pretreatment level (greater than 20 ng/ml). In the group treated with desipramine no difference in therapeutic outcome was obtained between patients with low and high pretreatments levels of 5-HIAA in the CSF. Attempts to correlate the steady state plasma concentrations of zimelidine, norzimelidine and desipramine with the therapeutic effect were unsuccessful. The plasma concentration of norzimelidine demonstrated a significant (P less than 0.05) positive correlation with age. The mean value of the uptake of 14C-5-HT in the patient's platelets, when measured before the treatment, was significantly (P less than 0.05) lower than found in a control group. Zimelidine, mainly via its metabolite norzimelidine, caused a pronounced inhibition of uptake of 14C-5-HT in platelets, decrease in whole blood 5-HT and inhibition of accumulation of 14C-5-HT in rat hypothalamic synaptosomes incubated in the patients plasma. Desipramine produced a slight inhibition of accumulation of 14C-5-HT in rat synaptosomes, but a marked inhibition of uptake of 14C-5-HT in the patient's platelets and a decrease in whole blood 5-HT. The accumulation of 3H-NA in rat synaptosomes incubated in the patient's plasma was strongly inhibited by desipramine treatment but only slightly affected by zimelidine.

Determination of amitriptyline-N-oxide, amitriptyline and nortriptyline in serum and plasma by high-performance liquid chromatography

A method for the determination of amitriptyline-N-oxide, amitriptyline and nortriptyline in serum and plasma has been developed. After extraction from serum or plasma the drugs were analysed by high-performance liquid chromatography. The detection limit was 10 ng/ml (2 ml serum or plasma actually used). The coefficient of variation for all three compounds was below 10%. Amitriptyline-N-oxide was found in rat plasma after an oral dose (10 mg/kg) of amitriptyline-N-oxide.

Technical considerations in the gas chromatographic analysis of desipramine

Procedures are presented for minimizing variability in and interferences with the gas chromatographic determination of desipramine in plasms. Careful consideration of procedures for sample collection and storage, drug separation from matrix components, and chromatography appears to be a prerequisite for avoiding inaccurate and imprecise determinations of this antidepressant, especially at levels below 20 micrograms/l. Numerous pitfalls are examined and optimal conditions for obviating them are presented.

Analysis of tricyclic antidepressant drugs by gas chromatography using nitrogen-selective detection with packed and capillary columns

A gas chromatographic method using either a conventional packed column (3% SP-2250) or a capillary column (SE-30) for the measurement of therapeutic plasma concentrations of tricyclic antidepressant drugs and their demethylated metabolites is described. The technique is based on a simple hexane extraction of drugs from alkalinized plasma followed by derivatization with heptafluorobutyric anhydride for the measurement of demethylated compounds. Subsequently, parent drugs and derivatives are chromatographed and detected using a nitrogen-selective detector. A comparison of the results using both types of chromatographic systems is discussed.

Simplified method for determination of the tetracyclic antidepressant mianserin in human plasma using gas chromatography with nitrogen detection

A simplified gas chromatographic method for determination of the antidepressant drug mianserin in human plasma is described. Application of a nitrogen-sensitive detector reduces the assay procedure to extraction, concentration and gas chromatographic determination. The method is suitable to determine mianserin in human plasma at the 1 ng/ml level on a routine basis. At the 20 ng/ml level the deviation of the mean from the true value and the relative standard deviation amount to 1.0% and 6.8%, respectively.