Ion-pair liquid chromatography of steady-state plasma levels of chlorimipramine and demethylchlorimipramine

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.

Noradrenergic function in obsessive-compulsive disorder: behavioral and neuroendocrine responses to clonidine and comparison to healthy controls

To evaluate noradrenergic (NE) function in obsessive-compulsive disorder (OCD), behavioral, physiological, and neuroendocrine responses to the alpha 2-adrenergic agonist clonidine were examined in 18 patients with OCD and 10 healthy subjects. Subjects received single i.v. doses of 2 micrograms/kg of clonidine administered under double-blind, placebo-controlled, random-assignment conditions. Following clonidine, but not following placebo, patients transiently experienced a significant reduction of obsessions and compulsions. Significant drowsiness and a reduction in anxiety were also noted, but the antiobsessional effect appeared independent of the soporific and antianxiety effects. Growth hormone (GH), cortisol, and 3-methoxy-4-hydroxyphenylglycol responses to clonidine did not differentiate patients from healthy controls. Blood pressure and pulse in response to clonidine did not differ between groups. Improvement in OCD symptoms after clonidine significantly correlated with GH response to clonidine, suggesting specific noradrenergic mediation. This finding lends only partial support for a primary defect of noradrenergic function in OCD.

Lower 3H-imipramine binding in platelets from untreated depressed patients compared to healthy controls

3H-Imipramine binding in platelets was measured in 63 severely depressed hospitalized patients, who had been drug free (with the exception of moderate doses of benzodiazepines) for at least 1 month, and in 53 healthy control subjects of comparable age and sex distribution. Bmax of 3H-imipramine binding was significantly lower in the depressed subjects (1012 +/- SD 295 vs. 1123 +/- SD 178 fmole/mg protein). Depressed patients who had attempted suicide by violent means tended to have higher Bmax than nonviolent attempters.

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.

Determination of citalopram, amitriptyline and clomipramine in plasma by reversed-phase high-performance liquid chromatography

The determination of citalopram, amitriptyline, clomipramine and their desmethyl metabolites after alkaline diethyl either extraction from plasma is achieved by high-performance liquid chromatography using two internal standards and mu Bondapak C18 as stationary phase. Elution is carried out isocratically at 0.5 or 1 ml/min with a mixture of acetonitrile-potassium dihydrogen phosphate-distilled water (45:50:5). Detection is monitored by absorption at 254 nm. The detection limit is less than 5 ng/ml for each compound. The coefficients of variation are between 1.3% and 9.4% for 8-360 ng/ml. Interference from 22 possible co-medications is discussed. The technique can be used for therapeutic monitoring of these antidepressants as well as in analytical toxicology.

CSF monoamine metabolites of depressed patients during illness and after recovery

Repeated lumbar punctures in 16 healthy volunteers showed reproducible concentrations of 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA) in cerebrospinal fluid (CSF). In seven depressed patients, studied during two or three illness periods, the metabolite concentrations were also fairly stable. In 11 patients CSF concentrations of 5-HIAA, but not of HVA, were higher after recovery than during depression. This increase of 5-HIAA after recovery was confined to patients whose initial serotonin metabolite levels were low. The finding constitutes further evidence of a biochemical heterogeneity within the depressive disorders, and suggests that patients whose CSF 5-HIAA is low during a depressive episode may have a less stable serotonin system than other patients with depressive illness.

CSF monoamine metabolites in melancholia

The neurotransmitter metabolites 5-hydroxyindoleacetic acid (5-HIAA), homovanillic acid (HVA) and 4-hydroxy-3-methoxyphenyl glycol (HMPG) in cerebrospinal fluid (CSF) were measured by mass fragmentography in 83 patients with melancholia (diagnosed by the Newcastle Inventory and the Research Diagnostic Criteria), and 66 healthy volunteer controls. After adjustment by analysis of covariance for differences between the subject groups in body height, age and sex distribution, significantly (P less than 0.001) lower concentrations of 5-HIAA and HVA were found in the melancholia patients than in the controls. HMPG did not differ between the groups. The differences could not be accounted for by differences in timing or examination techniques, and not by previously administered drugs (all patients were drug-free at the examination, but a minority had taken small amounts of psychotropic drugs prior to the wash-out period). The differences persisted after excluding the suicidal patients. There were no clear-cut differences between unipolar and bipolar patients. It is suggested that the reduced concentrations of 5-HIAA and HVA in the melancholic patients may be due to altered serotonin and/or dopamine functions in the central nervous system, which may be connected with an increased vulnerability to certain types of affective illness.

Do evacuated blood collection tubes interfere with therapeutic drug monitoring?

The influence of various brands of evacuated blood collection systems (the old type, red stoppered Vacutainer; the new type, blue stoppered Vacutainer; Monoject and Venoject) on therapeutic drug monitoring was investigated. No interferences were found in the assay of ethosuximide, phenobarbital, phenytoin, valproic acid, digitoxin, digoxin, procainamide, gentamicin and theophylline. Using Monoject and old type Vacutainer tubes, lower levels were found in the disopyramide assay: 91.3 +/- 4.6% (p less than 0.05) and 91.7 +/- 7.0% (not significant) respectively, and in the quinidine assay: 82.8 +/- 6.7% (p less than 0.02) and 83.9 +/- 4.4% (p less than 0.001) respectively as compared with glass tubes. In the carbamazepine assay a decrease was found in the Monoject tubes only: 93.7 +/- 1.7% (p less than 0.01). The stoppers of Monoject tubes and the old type Vacutainer tubes contained the plasticizer tris-(2-butoxyethyl)phosphate (TBEP), which has been shown to be a potent inhibitor of the binding of several drugs to alpha 1-acid glycoprotein. Using the new type Vacutainer and the Venoject, no interferences were found.

A collection of therapeutic, toxic and fatal blood drug concentrations in man

In order to assess the significance of drug concentrations measured in clinical and toxicological investigations, it is essential that good collections of data are readily available. As a guide to interpreting findings, the present work provides a compilation of therapeutic, toxic and fatal blood concentration ranges of 298 drugs of interest to clinical pharmacologists, clinical toxicologists, and forensic toxicologists. Wherever possible, ranges are expressed concisely in terms of the maximum blood concentrations which account for 10, 50 and 90% of the data collected. They provide easy access to the most reliable information which relates the blood drug concentration to the biological response it produces. Where appropriate, the different toxic effects of a drug and/or the different degrees of severity of toxic symptoms associated with different drug levels are clearly defined. The original sources of all data used are provided to allow the analyst to obtain further analytical, pharmacokinetic and toxicological information should this be necessary. Those factors (e.g. age, capacity for drug metabolism, drug interactions, etc) which can modify the relationship between a drug concentration and the response it produces are briefly discussed.

The analysis of tricyclic antidepressant drugs at therapeutic blood levels by reversed-phase high-performance liquid chromatography using pairing and organic counter-ions

A serum assay method incorporating two internal standards suitable for routine clinical analysis of tricyclic antidepressant drugs at the therapeutic level is described. The method involves extraction and chromatography using a reversed-phase high-performance liquid chromatography system incorporating pairing and organic counter-ions. The quantitative characteristics of the method are reported and results are compared with consensus values for four commonly encountered drugs, amitriptyline, nortriptyline, imipramine and desipramine. The method is shown to be applicable to more recently developed antidepressants such as nomifensine and maprotiline and the flexibility of the chromatography is discussed. Sample chromatograms obtained from patient samples in the presence and absence of potentially interfering drugs and metabolites are discussed.

Inhibitors of serotonin and noradrenaline uptake in human plasma after withdrawal of zimelidine and clomipramine treatment

Ten patients with endogenous depression, who had not taken any antidepressive drugs for 3 months, were treated with 100 mg b.i.d. zimelidine (five patients) or 75 mg b.i.d. clomipramine (five patients) for 5-10 weeks. Blood samples taken before and at various times after stopping the treatment were analysed for plasma concentrations of the drugs and their desmethylated metabolites, the uptake of 14C-serotonin in platelets incubated in platelet rich plasma, the concentration of serotonin in whole blood, and the inhibitory effect of the plasma on the accumulation of 14C-serotonin and 3H-noradrenaline in rat hypothalamic synaptosomes. It was found that these uptake measures were normalized within 1 to 2 weeks after zimelidine withdrawal, whereas the effects after clomipramine persisted for 3 to 4 weeks. Norzimelidine, the desmethylated metabolite of zimelidine, caused the effects after zimelidine treatment. Both clomipramine and its metabolite desmethylclomipramine were involved in uptake inhibition after clomipramine treatment. The mean pretreatment values of 14C-serotonin uptake in the platelets did not differ significant from an age and sex matched control group.l

Fluvoxamine and chlorimipramine in endogenous depression

Thirty patients were treated in a randomised double-blind efficacy study of fluvoxamine and chlorimipramine. The dose range for both drugs was 50-300 mg in divided daily doses. Mean daily doses were higher for fluvoxamine than chlorimipramine. Generally the baseline recordings were comparable for both drug groups. Fluvoxamine was superior to chlorimipramine in all the rating scales used without achieving statistical significance. Chlorimipramine, but not fluvoxamine, caused a significant decrease in blood pressure. There were no significant effects on ECG or laboratory variables. There was no significant relationship between plasma levels of either compound or metabolite and clinical response. Chlorimipramine exerted more unwanted effects than fluvoxamine. Autonomic effects of fluvoxamine were minimal in comparison with chlorimipramine. Chlorimipramine patients required more concurrent anxiolytic medication than fluvoxamine. Both drug groups required a significant amount of concurrent hypnotic medication.

Platelet MAO activity and monoamine metabolites in cerebrospinal fluid in depressed and suicidal patients and in healthy controls

Platelet monoamine oxidase (MAO) activity and cerebrospinal fluid (CSF) concentrations of 5-hydroxyindoleacetic acid (5HIAA), homovanillic acid (HVA), and 4-hydroxy-3-methoxyphenylglycol (HMPG) were simultaneously measured in 20 currently depressed patients, 11 recovered depressed patients, 15 nondepressed suicide attempters, and 42 healthy control subjects. Both 5HIAA and HVA were positively and significantly correlated to platelet MAO activity in the healthy subjects, but not in any of the patient groups. Suicide attempters had significantly lower CSF 5HIAA than nonsuicidal patients.

Determination of clomipramine or imipramine and their mono-demethylated metabolites in human blood or plasma by high-performance liquid chromatography

A high-performance liquid chromatographic method for the quantitative assay of clomipramine or imipramine and their mono-demethylated metabolites in human blood or plasma is described. After addition of the internal standards, imipramine for clomipramine, desipramine for desmethylclomipramine and conversely, the compounds are extracted from blood or plasma at pH 10 into heptane containing 1% isoamyl alcohol; they are then back-extracted into an acidic aqueous phase and re-extracted at a basic pH into heptane. After evaporation, the residue is dissolved in 300 microliters of mobile phase and 150 microliters is injected. Both drugs and their mono-demethylated metabolites are well separated from the blood or plasma components and the other metabolites on a silica gel column using ethanol--hexane-dichloromethane-diethylamine (30:62:8:5 . 10(-3)) as the mobile phase at a flow-rate of 1.5 ml/min. The limit of sensitivity is 5 ng/ml for clomipramine and imipramine and 10 ng/ml for the corresponding mono-demethylated metabolites. This method has been used to analyse plasma from subjects given therapeutic doses of clomipramine or imipramine.

Biochemical effects of zimelidine in man

The novel drug zimelidine 50--300 mg/day was administered to 12 depressed patients. After about 3 weeks plasma levels of the demethyl metabolite, norzimelidine, were almost thrice those of the parent drug. During incubation of slices of rat brain cortex in plasma from the treated patients, the neuronal uptake of serotonin and noradrenaline was 51.7 +/- 10.2 and 82.8 +/- 9.6%, respectively, of the control values. The uptake inhibition both of serotonin and noradrenaline was correlated with the plasma level of norzimelidine (r = 0.62 and 0.63, respectively). The major central metabolites of serotonin (5-HIAA) and noradrenaline (HMPG) in cerebrospinal fluid (CSF) decreased significantly (29 and 11%, respectively) during treatment with zimelidine. Although there was no mean change in the major dopamine metabolite (HVA) in CSF, the level during treatment (as percentage of the pretreatment level) was correlated with the effect of 5-HIAA in CSF. Thus, administration of zimelidine caused a relatively selective inhibition of serotonin uptake, mainly due to norzimelidine. A small but significant inhibition of noradrenaline uptake was also seen, but this effect was less pronounced than during chlorimipramine treatment. There was an effect on the dopaminergic system, probably secondary to the action of serotonergic neurons.

Disease-induced changes in the plasma binding of basic drugs

The plasma binding of basic (cationic) drugs differs from that of the more completely studied acidic drugs. Basic drugs associate with a number of plasma constituents. alpha 1-Acid glycoprotein, lipoprotein, and albumin all appear to play an important role in the binding of most of these drugs. Acidic drugs bind largely to albumin. The variation in plasma albumin is relatively narrow and is almost always in the direction of decreased concentrations. alpha 1-Acid glycoprotein and lipoproteins show large fluctuations due both to physiological and pathological conditions. Decreases and increases in concentration have been observed. Associated with these changes in binding proteins, both decreases and increases in plasma binding of basic drugs have been recorded. Increased binding with disease appears to be virtually unique to basic drugs. The implications of these newly described disease-induced increases in plasma binding have yet to be explored. With the limited information in hand the following consequences are predicted. Increased binding will tend to decrease the volume of distribution of total (bound plus free) drug. The clearance will be unchanged or decreased depending upon the initial clearance of the drug and the avidity of the protein binding. As the half-life depends upon both clearance and volume of distribution, changes in it will be variable, depending upon changes in these two parameters. It is predicted that the area under the free drug plasma concentration-time curve will decrease with increasing binding after an intravenous dose while it will be unchanged after an oral dose. The relationship of total drug plasma concentration to free drug concentration will change with changes in binding. Thus plasma concentration monitoring of drug therapy by use of total drug concentrations will be inaccurate in situations in which large variations in binding occur. Misinterpretations of both therapeutic monitoring and pharmacokinetics studies in disease states with altered binding are likely unless these changes are appreciated.

Monitoring of antidepressant drug plasma levels: the next ten years

Future studies of the relationship between plasma level and drug response in depressed patients ought to take the following facts into consideration: 1. Selective drug analytical methods must be used and subjected to quality control. Methods for the major urinary metabolite(s) of the parent drug should also be developed. 2. Each drug has individual pharmacokinetic and pharmacodynamic properties--it is unlikely that one drug will be effective in all patients even under optimal kinetic conditions. 3. The pharmacologic and biochemical effects of hitherto investigated tricyclic antidepressants correlate significantly to the concentrations of parent drug and/or its active metabolite in plasma. 4. It is more likely that a significant correlation will be found between the total tricyclic antidepressant level in plasma and the therapeutic outcome in a patient sample if the range of plasma levels is large--in this case the relatively small interindividual differences in plasma protein binding play a minor role. 5. Concomitant somatic disease may change the kinetics of antidepressant drugs. 6. The clinical methods used for selecting and rating study patients with depressive disorders must be standardized. 7. Novel rapidly acting drugs are desirable because the slow onset of action of tricyclic antidepressant seriously hamper their clinical evaluation. 8. A strong correlation between plasma concentration of an antidepressant drug and clinical outcome is strong evidence that the clinical effect is due to the drug rather than nonpharmacological factors.

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

A simplified gas chromatographic method for the rapid measurement of tricyclic antidepressant drugs in plasma using a nitrogen-sensitive detector is described. All drugs are extracted and chromatographed under identical conditions. Tertiary amines are separated from their secondary amine metabolites, which are determined simultaneously without the need for derivatisation. The lower limit of accurate determination for most drugs is 10 microgram/1. The method has been applied to the routine measurement of amitriptyline and nortriptyline in plasma from patients receiving antidepressant treatment. Large and important interindividual differences in plasma concentrations in the patients investigated have been found, and the significance of these results is discussed.

Ion-pair liquid chromatography of amitriptyline and metabolites in plasma

A method is described for the determination of amitriptyline and nortriptyline in the plasma of patients during treatment. The method is based on liquid chromatography of the amines as ion-pairs with perchlorate. The separation column is packed with silica gel, and a mixture of diisopropyl ether, dichloromethane, methanol and water containing the counter ion is used as eluent. High efficacy and stability of the system is achieved. The separation of metabolites is demonstrated. The cis- and trans-10-hydroxy isomers of amitriptyline and nortriptyline are easily resolved with this chromatographic system.