Green HPLC-DAD and HPTLC Methods for Quantitative Determination of Binary Mixture of Pregabalin and Amitriptyline Used for Neuropathic Pain Management.

First analytical methods were herein developed for determination of pregabalin (PGB) and amitriptyline (AMT) as an active binary mixture used for management of neuropathic pain whether in pure forms or in human biological fluids (plasma/urine). First method is green high-performance liquid chromatography-diode array detector (HPLC-DAD) after derivatization of PGB with ninhydrin (NIN) on a reversed-phase C18 column using a mobile phase consisting of ethanol:water (97:3%, v/v) pumped isocratically at 0.8 mL/min; AMT were scanned at 215 nm, whereas PGB-NIN was scanned at 580 nm. Second method is High-performance thin-layer chromatography (HPTLC), where PGB and AMT were separated on silica gel HPTLC F254 plates, using ethanol:ethyl acetate:acetone:ammonia solution (8:2:1:0.05, by volume) as a developing system. AMT peaks were scanned at 220 nm, whereas PGB peaks were visualized by spraying 3% (w/v) ethanolic NIN solution and scanning at 550 nm. Linear calibration curves were obtained for human plasma and urine spiked with PGB and AMT over the ranges of 5-100 µg/mL and 0.2-2.5 µg/band for PGB, and 1-100 µg/mL and 0.1-2.0 µg/band for AMT for HPLC-DAD and HPTLC methods, respectively. The suggested methods were validated according to Food and Drug Administration guidelines for bioanalytical methods validation and they can be applied for routine therapeutic drug monitoring for the concerned drugs.

Analysis of smoking behavior on the pharmacokinetics of antidepressants and antipsychotics: evidence for the role of alternative pathways apart from CYP1A2.

Smoking is common among psychiatric patients and has been shown to accelerate the metabolism of different drugs. We aimed to determine the effect of smoking on the serum concentrations of psychopharmacological drugs in a naturalistic clinical setting. Dose-corrected, steady-state serum concentrations of individual patients were analyzed retrospectively by linear regression including age, sex, and smoking for amitriptyline (n=503), doxepin (n=198), mirtazapine (n=572), venlafaxine (n=534), clozapine (n=106), quetiapine (n=182), and risperidone (n=136). Serum levels of amitriptyline (P=0.038), clozapine (P=0.02), and mirtazapine (P=0.002) were significantly lower in smokers compared with nonsmokers after correction for age and sex. In addition, the ratios of nortriptyline/amitriptyline (P=0.001) and nordoxepin/doxepin (P=0.014) were significantly higher in smokers compared with nonsmokers. Smoking may not only induce CYP1A2, but may possibly also affect CYP2C19. Furthermore, CYP3A4, UGT1A3, and UGT1A4 might be induced by tobacco smoke. Hence, a different dosing strategy is required among smoking and nonsmoking patients. Nevertheless, the clinical relevance of the results remained unclear.

Magnetic micro-solid-phase extraction based on magnetite-MCM-41 with gas chromatography-mass spectrometry for the determination of antidepressant drugs in biological fluids.

A new facile magnetic micro-solid-phase extraction coupled to gas chromatography and mass spectrometry detection was developed for the extraction and determination of selected antidepressant drugs in biological fluids using magnetite-MCM-41 as adsorbent. The synthesized sorbent was characterized by several spectroscopic techniques. The maximum extraction efficiency for extraction of 500 µg/L antidepressant drugs from aqueous solution was obtained with 15 mg of magnetite-MCM-41 at pH 12. The analyte was desorbed using 100 µL of acetonitrile prior to gas chromatography determination. This method was rapid in which the adsorption procedure was completed in 60 s. Under the optimized conditions using 15 mL of antidepressant drugs sample, the calibration curve showed good linearity in the range of 0.05-500 µg/L (r2  = 0.996-0.999). Good limits of detection (0.008-0.010 µg/L) were obtained for the analytes with good relative standard deviations of <8.0% (n = 5) for the determination of 0.1, 5.0, and 500.0 µg/L of antidepressant drugs. This method was successfully applied to the determination of amitriptyline and chlorpromazine in plasma and urine samples. The recoveries of spiked plasma and urine samples were in the range of 86.1-115.4%. Results indicate that magnetite micro-solid-phase extraction with gas chromatography and mass spectrometry is a convenient, fast, and economical method for the extraction and determination of amitriptyline and chlorpromazine in biological samples.

The association between pro-arrhythmic agents and aortic stenosis in young adults: is it sufficient to clarify the sudden unexpected deaths?

Most young patients with mild-to-moderate aortic stenosis show no symptoms, and sudden death appears only occasionally. We hypothesised that malignant ventricular arrhythmias could be responsible for the high incidence of sudden death in such patients. If multiple factors such as asymptomatic aortic stenosis in association with arrhythmia-provoking agents are involved, could it be sufficient to account for sudden unexpected death? In this study, eight cases of sudden death in young adults, with ages ranging from 22 to 36 years, who had never reported any symptoms that could be related to aortic stenosis, were investigated. Full autopsies were performed, and congenital aortic stenosis in all eight cases was confirmed. DNA testing for channelopathies was negative. Comprehensive toxicological analyses found an electrolyte imbalance, or non-toxic concentrations of amitriptyline, terfenadine, caffeine, and ethanol. Collectively, these results suggest that congenital asymptomatic aortic stenosis without cardiac hypertrophy in young adults is not sufficient to cause sudden death merely on its own; rather, an additional provoking factor is necessary. According to our findings, the provoking factor may be a state of physical or emotional stress, a state of electrolyte imbalance, or even taking a therapeutic dose of a particular drug.

Magnetic beads as an extraction medium for simultaneous quantification of acetaminophen and structurally related compounds in human serum.

This paper describes a sample preparation method that complements a previously published liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay for acetaminophen and eight structurally-related compounds in human serum (C. Bylda, R. Thiele, U. Kobold, D.A. Volmer. Drug Test. Anal. 2014, 6, 451). The analytes (acetaminophen [APAP] + metabolites acetaminophen-glucuronide [APG], -cysteine [APC], -mercapturate [APM] and -cysteine [APC], structurally similar analogues phenacetin and p-phenetidine, as well as tricyclic antidepressants imipramine and amitryptiline) were extracted from serum using magnetized hyper-crosslinked polystyrene particles. The sample preparation protocol was developed by means of a design of experiments (DoE) statistical approach. Using three representative compounds from the analyte panel with different polarities (high, medium, and low), two screening designs were used to identify factors that exhibited significant impact on recovery of the analytes. These parameters were then optimized to permit extraction of the complete target panel exhibiting a broad range of chemical polarities. Liquid chromatographic separations were achieved by gradient elution using a pentafluorphenyl column with subsequent detection by electrospray ionization-triple quadrupole mass spectrometry in multiple reaction monitoring (MRM) mode. The method was linear over the range 0.1-100 µg/mL for APAP, APG, p-phenetidine and phenacetin, 0.03-50 µg/mL for APS, and 0.01-10 µg/mL for APM, APC, imipramine and amitriptyline, with R(2) > 0.99. The assay exhibited good precision with CVs ranging from 2 to 9% for all analytes; the accuracy was assessed by comparing two LC-MS/MS methods using a set of 68 patient samples.

Pharmacokinetics of Amitriptyline HCl and Its Metabolites in Healthy African Grey Parrots ( Psittacus erithacus ) and Cockatoos (Cacatua Species).

Amitriptyline, a tricyclic antidepressant, is used clinically to treat feather-destructive behavior in psittacine birds at a recommended dosage of 1-5 mg/kg PO q12-24h, which has been extrapolated from human medicine and based on anecdotal reports. The purpose of this pilot study was to describe the individual and population pharmacokinetic parameters of amitriptyline after a single oral dose at 1.5 mg/kg, 4.5 mg/kg, and 9 mg/kg in healthy African grey parrots ( Psittacus erithacus , n = 3) and cockatoos (Cacatua species, n = 3). Three birds received an initial 1.5 mg/kg oral dose, and blood samples were collected for 24 hours at fixed time intervals. Serum concentrations of amitriptyline and its metabolites were determined by polarized immunofluorescence. After determining the initial parameters and a 14-day washout period, 2 African grey parrots and 1 cockatoo received a single oral dose at 4.5 mg/kg, and 3 cockatoos and 1 African grey parrot received a single oral dose at 9 mg/kg. Concentrations reached the minimum therapeutic range reported in people (60 ng/mL) in 4 of 10 birds (4.5 and 9.0 mg/kg). Concentrations were within the toxic range in 1 African grey parrot (9 mg/kg), with regurgitation, ataxia, and dullness noted. Serum concentrations were nondetectable in 3 birds (1.5 and 4.5 mg/kg) and detectable but below the human therapeutic range in 3 birds (1.5 mg/kg and 9 mg/kg). Drug concentrations were continuing to increase at the end of the study (24 hours) in 1 bird. Elimination half-life varied from 1.6 to 91.2 hours. Population pharmacokinetics indicated significantly varied absorption, and elimination constants varied between species. Although amitriptyline appeared to be tolerated in most birds, disposition varies markedly among and within species, between the 2 genera, and within individual birds. The current recommended dosage of 1-5 mg/kg q12h in psittacine birds appears insufficient to achieve serum concentrations within the human therapeutic range and does not yield predictable concentrations. Results of this study suggest doses of up to 9 mg/kg may be necessary, although that dose may produce adverse events in some birds, and elimination half-life is sufficiently variable that dosing intervals are not predictable. Therapeutic drug monitoring combined with response to therapy is indicated to determine individual therapeutic ranges.

Ultrasound-assisted combined with nano-sized molecularly imprinted polymer for selective extraction and pre-concentration of amitriptyline in human plasma with gas chromatography-flame detection.

A new process was developed for the selective extraction and pre-concentration of amitriptyline (AT) from human plasma using nano-sized molecularly imprinted polymer (MIP) with ultrasound-assisted extraction (UAE). The nano-sized AT imprinted polymer particles were synthesized using suspension polymerization in silicon oil and characterized by Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscope (SEM) methods. With the application of optimized values, linearity values in the ranges of 20-200µgmL(-1) and 35-200µgmL(-1) were obtained for AT with the correlation of determination values (r(2)) 0.998 and 0.995 in water and plasma, respectively. The limits of detections (S/N=3) for AT were found to be 0.7 and 1.2µgmL(-1) in water and plasma, respectively. The enrichment factors of AT in water and plasma were 52 and 40, respectively. The inter-day precisions (%) were in the range of 5.8-9.2%. Relative recovery rates ranged from 82.4% to 92.3%. The method was successfully applied to determine AT in the human plasma samples.

Simultaneous quantification of acetaminophen and structurally related compounds in human serum and plasma.

The method described in this study allows the simultaneous quantification of acetaminophen (APAP) and nine structurally related compounds, namely acetaminophen metabolites and structurally similar analogs (acetaminophen-glucuronide [APG], -sulfate [APS], mercapturate [APM], -cysteine [APC], p-phenetidine, phenacetin), antidote (N-acetylcysteine, NAC), and two tricyclic antidepressants (imipramine and amitryptiline). Due to the relatively high serum concentration levels in the µg/ml range, matrix effects were simply minimized by dilution. The samples were diluted with water and disulfide bonds between serum proteins and analytes reduced using tris(2-carboxyethyl)phosphine. Chromatographic separation of the analytes was achieved by gradient elution using a pentafluorphenyl (PFP) column with subsequent detection by electrospray ionization (ESI) triple quadrupole mass spectrometry in positive and negative ionization multiple reaction monitoring (MRM) modes. Quantification was performed by means of deuterated analogues of the analytes as internal standards. Total run time of the assay was 19 min. The method was fully validated and allowed quantification of the analytes with lower limits of quantification between 50 and 0.5 ng/ml. The calibration curves were linear over the range 0.1-100 µg/ml for APAP, APG, NAC, p-phenetidine and phenacetin, 0.03-50 µg/ml for APS, and 0.01-10 µg/ml for APM, APC, imipramine and amitriptyline with correlation coefficients r(2) > 0.99. The intra-assay precision was ≤5% for all analytes except NAC (CV < 10%). The inter-day precision was ≤10% for all analytes except NAC (inter-assay precision <11%). This method was used to analyze 77 patient and spiked samples and results were consistent with expected values from a round robin test.

UGT2B7 genetic polymorphisms are associated with the withdrawal symptoms in methadone maintenance patients.

AIM: To test whether the genetic polymorphisms within the gene encoding the UGT2B7 gene may have an impact on methadone treatment. MATERIALS & METHODS: Twelve SNPs in UGT2B7 were selected. 366 methadone maintenance treatment patients in Taiwan were recruited and genotyped. RESULTS: In a genotype recessive model, rs6600879, rs6600880, rs4554144, rs11940316, rs7438135, rs7662029, rs7668258, rs7439366, rs4292394 and rs6600893 showed significant associations with severity of withdrawal symptoms (permutation p < 0.002), pupil size (permutation p < 0.048) and tremor (permutation p < 0.008). Haplotypes of GATCAGCCGC and CTCTGATTCT were significantly associated with pupil size score and tremor score (p < 0.034). CONCLUSION: These results suggest that SNPs of the UGT2B7 gene may play important roles in opiate withdrawal symptoms.

Genetic polymorphisms in CYP3A4 are associated with withdrawal symptoms and adverse reactions in methadone maintenance patients.

AIM: Methadone maintenance therapy is one of the standard treatments for heroin addiction. The isozyme CYP3A4 of the CYP system is one of the metabolic enzymes, as well as CYP2B6, responsible for the metabolism of methadone. The aim of the present study is to evaluate the potential use of genetic polymorphisms in CYP3A4 as biomarkers for the prediction of methadone treatment responses. MATERIALS & METHODS: A total of 366 Han Chinese methadone maintenance treatment patients in Taiwan were recruited in this study. Main clinical assessments included the clinical opioid withdrawal scale (COWS), the treatment emergent symptom scale (TESS) and the plasma concentrations of methadone and its metabolites. Genetic associations of six SNPs in the CYP3A4 gene were calculated using a general linear model. RESULTS: Genotypes and allele types of rs4646440 and rs2242480 were found to be significantly associated with the severity of withdrawal symptoms rated by COWS (p = 0.012, 0.0096, 0.017 and 0.012, respectively) as well as the side effects rated by TESS (p = 0.0089, 0.028, 0.0027 and 0.0085, respectively). The allele types associated with more severe withdrawal symptoms are also associated with more severe side effects and less betel nut (Areca catechu) use (p = 0.009 for rs4646440, p = 0.0063 for rs2242480). Further analyses on specific withdrawal symptoms in COWS showed that the genetic variants in rs4646440 are significantly associated with heart rate (allele type p = 0.0019). CONCLUSION: These results suggested that genetic variants in the CYP3A4 gene may be useful indicators for the severity of side effects and withdrawal symptoms for methadone treatment.

Evaluation of risk factors for elevated tricyclic antidepressant plasma concentrations.

PURPOSE: To quantify the effect of clinical and demographic factors on the risk of elevated and toxic tricyclic antidepressant (TCA) plasma concentrations (Cp) and to describe the rates of elevated and toxic TCA Cp. METHODS: This matched, case-control study was conducted among adult patients enrolled in a group model HMO who had a TCA Cp laboratory measurement and purchased at least one TCA prescription for either amitriptyline or nortriptyline during the 70 days preceding the TCA Cp measurement. Predictive models of experiencing an elevated or toxic Cp were created using multivariate conditional logistic regression. RESULTS: At least one Cp was drawn in 1057 unique patients with a TCA purchase. Of these, 18.4% (194/1057) patients (cases) had an elevated TCA Cp and were matched to 716 non-elevated Cp patients. Additionally, 27.3% (53/194) of the cases (matched to 196 controls) experienced a toxic TCA Cp. The best fitting model of an elevated TCA Cp included TCA dose category (daily doses >or=150 mg, OR = 4.08; doses of 50 to <100 mg, OR = 0.36; and doses <50 mg, OR = 0.18, p < 0.05 for all comparisons), female gender (OR = 1.78, p < 0.05) and concurrent use of fluoxetine or paroxetine (OR = 1.75, p < 0.05). The best fitting predictive model of a toxic TCA Cp included the same factors as for the predictive model of an elevated TCA Cp. CONCLUSIONS: Recognizing and monitoring predictors of elevated or toxic TCA Cps, including increasing TCA dose, female gender, and concurrent use of fluoxetine or paroxetine, may reduce serious adverse drug reactions and deaths in the TCA-receiving patient population.

Serum anticholinergic activity in patients following cardiac surgery and healthy individuals following amitriptyline application.

The serum anticholinergic activity (SAA) is used as a marker for cognitive impairment. Here, two studies have been performed characterizing the SAA profile. In Study 1 the endogenous SAA in relation to the total serum protein concentration was monitored for 24 h in five healthy individuals and compared with that in four inpatients following cardiac surgery. In Study 2 the SAA of seven healthy individuals was assessed following a single amitriptyline dose. In both studies SAA was assessed by an ex vivo assay. In Study 1, the absolute SAA varied in a wide range of 1.2 and 14.5 atropine equivalents (AEs) over 24 h. A circadian pattern was not observed. The mean total serum protein concentration, but not the SAA, was significantly lower in inpatients than in healthy individuals. In Study 2, the SAA increased following amitriptyline to a maximum. The mean SAA increased by 6.39 AE at the amitriptyline peak concentration. High SAA variability showed a low statistical relation to amitriptyline concentrations. Both studies characterize the SAA as an individual parameter not affected per se by surgery or clinical care and poorly correlated with the total serum protein concentration. The relation with amitriptyline concentration helps to quantify SAA values towards a better understanding of the clinical implications and limitations of SAA changes.

[Gas chromatography with mass-selective detector in testing blood for amitriptyline and nortriptyline].

The article describes the method of simultaneous detection of amitriptiline and nortriptilin in cadaveric blood using gas chromatography with mass-selective detection. Preparation includes liquid-liquid extraction and derivation with trifluoroacetic anhydride. Nortriptilin threshold of detectability in the blood is 0.02 mcg/ml, amitriptilin one--0.05 mcg/ml. The range of detectability--0.05-3.0 mcg/ml for both compounds. Maximal error of the compounds detectability was under 12.9% for concentrations 0.10 mcg/ml and 10.6% for concentrations 2.0 mcg/ml. The method was tested on expert material in forensic chemical examinations.

Comparative assessment of blood and urine analyses in patients with acute poisonings by medical, narcotic substances and alcohol in clinical toxicology.

Acute poisonings by medical, narcotic substances and alcohol are actual in Russia in the recent years. Comparison of analytic facilities of modern analytical techniques: chromatographic (HPLC, GC, GC-MS) and immuno-chemical (FPIA) in clinical toxicology for urgent diagnostics, assessment of the severity of acute poisoning and the efficacy of the treatment in patients with acute poisonings by psychotropic drugs, narcotics and alcohol have been done. The object of the study were serum, blood, urine of 611 patients with acute poisonings by amitriptyline, clozapine, carbamazepine, opiates and also alcohol. Threshold concentrations (threshold, critical and lethal) of the toxicants and their active metabolites which corresponded to different degrees of poisoning severity have been determined. The most comfortable and informative screening method for express diagnostics and assessment of severity of acute poisonings by psychotropic drugs and narcotics showed the HPLC with using automatic analyzers. FPIA using the automatic analyzer could be applied for screening studies, if group identification is enough. GC-FID method is advisable in case of poisoning by medical substances and narcotics in view of repeated investigation for assessment of the efficacy of the therapy. GC-MS could be advisable for confirming the results of other methods. GC-TCD possess high sensitivity and specificity and is optimal for express differential diagnostics and quantitative assessment of acute poisoning by ethanol and other alcohols.

Topical amitriptyline and ketamine in neuropathic pain syndromes: an open-label study.

UNLABELLED: Twenty eight subjects with refractory, moderate to severe peripheral neuropathic pain participated in an open label prospective trial examining perceived analgesic effect, patient satisfaction, and safety of topical amitriptyline 2%/ketamine 1% cream. Outcome measures included an 11-point numerical rating scale for pain intensity (NRS-PI), a 5-point satisfaction scale, blood chemistry screen, drug and metabolite levels, urinalyses, electrocardiogram (ECG), and physical examination. Adverse events were monitored. Twenty-one subjects completed the trial. At 6 months, subjects reported an average long-term reduction in pain of 34% (standard deviation [SD] = 37%); 5 subjects (25%) achieved 50% or greater reduction in pain and 1 subject (5%) achieved 100% reduction in pain. At 12 months, the average reduction in pain was 37% (SD = 40%); 7 subjects (40%) achieved 50% or greater pain reduction. At the end of the study, 89% of subjects rated their satisfaction as 3/5 or greater and 2 subjects (10%) were pain free. Minimal adverse events were reported and there were no serious medication related adverse events. Blood levels revealed minimal systemic absorption. In conclusion, topical 2% amitriptyline/ 1% ketamine cream was associated with long-term reduction (6-12 months) in perceived pain, moderate to complete satisfaction, and was well tolerated in treatment of neuropathic pain. There was no significant systemic absorption of amitriptyline or ketamine. PERSPECTIVE: This study demonstrates that topical 2% amitriptyline/1% ketamine, given over 6-12 months, is associated with long-term perceived analgesic effectiveness in treatment of neuropathic pain. Antidepressants and ketamine both produce multiple pharmacologic effects that may contribute to peripheral analgesia; such actions include block of peripheral N-methyl-D-aspartate receptors, local anesthetic properties, and interactions with adenosine systems.

Isotope dilution gas chromatographic-mass spectrometric measurement of tricyclic antidepressant drugs. Utility of the 4-carbethoxyhexafluorobutyryl derivatives of secondary amines.

Stable isotope dilution gas chromatographic-mass spectrometric (GC-MS) measurement of tricyclic antidepressants (TCA) is a useful alternative to high-performance liquid chromatography (HPLC) methods when interfering substances prevent accurate quantitation by HPLC. For satisfactory GC-MS analysis, secondary amine TCA must be derivatized. Commonly employed trifluoroacetyl and heptafluorobutyryl derivatives are relatively unstable and cause rapid deterioration of capillary GC columns. Therefore we examined 4-carbethoxyhexafluorobutyryl chloride (CHFB-CI) as an alternative derivatizing agent and developed a stable isotope dilution GC-MS method employing ring-labeled [2H4]-desipramine and [2H4]-imipramine internal standards, which permits measurement of desipramine, nortriptyline, imipramine, and amitriptyline in plasma samples containing one or all of these analytes. The GC-MS assay is linear for each analyte from the lower limit of quantitation (25 ng/mL) up to 1500 ng/mL and correlates well with HPLC measurements. The GC-MS analytic coefficient of variation was 9.7 +/- 1.3% for all analytes considered together. Although interferences are observed in the HPLC assay, thioridazine, perphenazine, cyclobenzaprine, and norcyclobenzaprine do not interfere with GC-MS measurements of the TCA examined here. The stability of the CHFB derivative of secondary amine TCA was found to be superior to that of the trifluoroacetyl derivatives of these compounds.

Quantitative determination of tricyclic antidepressants and their metabolites in plasma by solid-phase extraction (Bond-Elut TCA) and separation by capillary gas chromatography with nitrogen-phosphorous detection.

An analytical method for the simultaneous determination of amitriptyline, nortriptyline, imipramine, desipramine, clomipramine, and desmethylclomipramine in human plasma using promazine as internal standard is described. The method is based on a solid-phase extraction procedure using the Bond-Elut TCA columns followed by separation and detection using capillary gas chromatography with a specific nitrogen phosphorous detector (GC/NPD). Using the new extraction procedure, the problem of adsorption losses was overcome, and good recoveries were achieved for all compounds tested (>87%). Furthermore, clean extracts free of chromatographic interferences were obtained. Complete separation of underivatized, tricyclic antidepressant compounds was achieved in <11 minutes with reliable chromatographic performance. The limits of detection ranged from 1.2 to 5.8 microg/l. Calibration curves, showing good linearity, were prepared covering the therapeutic concentrations range expected (20 to 500 microg/l). The interassay precision values (RSD) ranged from 4.5% to 9.8%. It is concluded that extraction of amitriptyline, nortriptyline, imipramine, desipramine, clomipramine, and desmethylclomipramine, with Bond Elut TCA solid-phase columns followed by their detection using GC/NPD provides a sensitive and reproducible method that can be easily automated for immediate and routine analysis of clinical samples.

[Treatment chronic pain with amitriptyline. A double-blind dosage study with determination of serum levels]. / Behandling av pasienter med kroniske smerter med amitriptylin. Dobbeltblind doseringsundersøkelse med serumkonsentrasjonsbestemmelse.

The aim of this study was to find an optimal analgesic dose of amitriptyline, and at the same time examine whether a therapeutic window existed for this analgesic effect. 85 patients with chronic, non-malignant pain were included in a double-blind treatment regime with four doses of amitriptyline (10, 25, 50 or 100 mg). A blood sample was taken at steady state. The results showed 25 mg amitriptyline to have a good analgesic and sleep regulatory effect. The four different doses of amitriptyline did not show any significant difference in efficacy. No therapeutic window was found, but one cannot exclude that it exists. Low-dose amitriptyline, as a non-addictive drug, is a good alternative in the treatment of chronic pain, independent of co-morbid depression.

Detection of tricyclic antidepressants in whole blood by headspace solid-phase microextraction and capillary gas chromatography.

A simple method for the extraction of four tricyclic antidepressants from whole blood by headspace solid-phase microextraction (SPME) is presented. The whole blood samples contain four drugs (amitriptyline, chlorimipramine, imipramine, and trimipramine) and are heated at 100 degrees C in a septum-capped vial in the presence of distilled water and NaOH solution; a polydimethylsiloxane-coated SPME fiber is exposed to the headspace of the vial to allow adsorption of the drugs before capillary gas chromatography (GC) with flame-ionization detection. The headspace SPME-GC produces intense peaks for each drug with very little background noise. Recoveries of the four drugs by the present method are 5.3-12.9%. The calibration curves for the drugs show linearity in the range of 31-1000 ng/0.5 mL. The detection limits of each drug are 16-25 ng/0.5 mL. Imipramine is detectable from rat blood 5 h after oral administration of imipramine (500 mg/kg body weight); the concentration is 1.44 +/- 0.209 micrograms/mL.