Effects of Pharmacogenetic Screening for CYP2D6 Among Elderly Starting Therapy With Nortriptyline or Venlafaxine: A Pragmatic Randomized Controlled Trial (CYSCE Trial).

PURPOSE/BACKGROUND: The duration of untreated depression is a predictor for poor future prognosis, making rapid dose finding essential. Genetic variation of the CYP2D6 isoenzyme can influence the optimal dosage needed for individual patients. The aim of this study was to determine the effectiveness of CYP2D6 pharmacogenetic screening to accelerate drug dosing in older patients with depression initiating nortriptyline or venlafaxine. METHODS/PROCEDURES: In this randomized controlled trial, patients were randomly allocated to one of the study arms. In the intervention arm (DG-I), the specific genotype accompanied by a standardized dosing recommendation based on the patients' genotype and the prescribed drug was directly communicated to the physician of the participant. In both the deviating genotype control arm (DG-C) and the nonrandomized control arm, the physician of the participants was not informed about the genotype and the associated dosing advise. The primary outcome was the time needed to reach adequate drug levels: (1) blood levels within the therapeutic range and (2) no dose adjustments within the previous 3 weeks. FINDINGS/RESULTS: No significant difference was observed in mean time to reach adequate dose or time to adequate dose between DG-I and DG-C. Compared with the nonrandomized control arm group, adequate drug levels were reached significantly faster in the DG-I group (log-rank test; P = 0.004), and there was a similar nonsignificant trend for the DG-C group (log-rank test; P = 0.087). IMPLICATIONS/CONCLUSIONS: The results of this study do not support pharmacogenetic CYP2D6 screening to accelerate dose adjustment for nortriptyline and venlafaxine in older patients with depression.

Amitriptyline accumulation in tissues after coated activated charcoal hemoperfusion-a randomized controlled animal poisoning model.

Amitriptyline poisoning (AT) is a common poisoning, and AT possess the ability to promote life-threatening complications by its main action on the central nervous and cardiovascular systems. The pharmacokinetic properties might be altered at toxic levels compared to therapeutic levels. The effect of coated activated charcoal hemoperfusion (CAC-HP) on the accumulation of AT and its active metabolite nortriptyline (NT) in various tissues was studied in a non-blinded randomized controlled animal trial including 14 female Danish Land Race piglets. All piglets were poisoned with amitriptyline 7.5 mg/kg infused in 20 min, followed by orally instilled activated charcoal at 30 min after infusion cessation. The intervention group received 4 h of CAC-HP followed by a 1-h redistribution phase. At study cessation, the piglets were euthanized, and within 20 min, vitreous fluid, liver tissue, ventricle and septum of the heart, diaphragm and lipoic and brain tissues were collected. AT and NT tissue concentrations were quantified by UHPLC-MS/MS. A 4-h treatment with CAC-HP did not affect the tissue accumulation of AT in the selected organs when tested by Mann-Whitney U test (p values between 0.44 and 0.73). For NT concentrations, p values were between 0.13 and 1.00. Although not significant, an interesting finding was that data showed a tendency of increased tissue accumulation of AT and NT in the CAC-HP group compared with the control group. Coated activated charcoal hemoperfusion does not significantly alter the tissue concentration of AT and NT in the AT-poisoned piglet.

Quantitative Modeling Analysis Demonstrates the Impact of CYP2C19 and CYP2D6 Genetic Polymorphisms on the Pharmacokinetics of Amitriptyline and Its Metabolite, Nortriptyline.

Amitriptyline is a tricyclic antidepressant that is metabolized mainly by CYP2C19 and CYP2D6 enzymes. Higher plasma levels of amitriptyline and its active metabolite, nortriptyline, are associated with an increased risk of adverse events including anticholinergic effects. The aim of this study was to evaluate the effects of CYP2C19 and CYP2D6 genetic polymorphisms on amitriptyline and nortriptyline pharmacokinetics. Twenty-four Korean healthy adult male volunteers were enrolled in the study after stratification by their CYP2C19 and CYP2D6 genotypes. Serial blood draws for pharmacokinetic analysis were made after a single oral 25-mg dose of amitriptyline was administered. Plasma amitriptyline and nortriptyline concentrations were measured by a validated liquid chromatography with tandem mass spectrometry. Population pharmacokinetic modeling analysis was conducted using NONMEM, which evaluated the effects of CYP2C19 and CYP2D6 genotypes on amitriptyline and nortriptyline pharmacokinetics. The biotransformation of amitriptyline into nortriptyline was significantly different between subjects with the CYP2C19*2/*2, *2/*3, and *3/*3 genotypes and those with the other genotypes, with an estimated metabolic clearance of 17 and 61.5 L/h, respectively. Clearance of amitriptyline through pathways other than biotransformation into nortriptyline was estimated as 18.8 and 30.6 L/h for subjects with the CYP2D6*10/*10 and *10/*5 genotypes and those with the other genotypes, respectively. This study demonstrated a quantitative effect of the CYP2C19 and CYP2D6 genotypes on amitriptyline and nortriptyline pharmacokinetics. Production of nortriptyline from amitriptyline was associated with CYP2C19 genotypes, and clearance of amitriptyline through pathways other than biotransformation into nortriptyline was associated with CYP2D6 genotypes. These observations may be useful in developing individualized, optimal therapy with amitriptyline.

In vitro assessment of competitive and time-dependent inhibition of the nevirapine metabolism by nortriptyline in rats.

Nevirapine (NVP) is a non-nucleoside reverse transcriptase inhibitor of human immunodeficiency virus type 1 (HIV-1) widely used as a component of High Active Antiretroviral Therapy (HAART) since it is inexpensive, readily absorbed after oral administration and non-teratogenic. In the present work, the mechanism of a previously described pharmacokinetic interaction between NVP and the antidepressant drug nortriptyline (NT) was studied using rat hepatic microsomes. The obtained results showed a competitive inhibition of the NVP metabolism by NT. The three main NVP metabolites (2-OH-NVP, 3-OH-NVP and 12-OH-NVP) where competitively inhibited with similar inhibitory constant values (Ki = 4.01, 3.97 and 4.40 µM, respectively). Time-dependent inhibition of the NVP metabolism was also detected, with a 2.5-fold reduction in the IC50 values of NT for 2-, 3-, and 12-OH-NVP formation when NT was preincubated with the microsomal suspension in the presence of an NADPH-generating system. A concentration-dependent inhibition of the formation of NVP metabolites by the main NT metabolite (10-OH-NT) was also observed, however, the inhibitory potency of 10-OH-NT was much lower than that of the parent drug. The apparent hepatic intrinsic clearance of NVP determined in these in vitro experiments was used to predict the in vivo clearance of NVP using the "well-stirred" and the "parallel-tube" models, resulting in values close to those previously observed in vivo clearance. Finally, a good prediction of the increase in the plasma concentrations of NVP when co-administered with NT was obtained employing the inhibitory constant of NT determined in vitro and the estimated plasma concentration of NT entering the liver.

Sex-dependent metabolism of nevirapine in rats: impact on plasma levels, pharmacokinetics and interaction with nortriptyline.

Nevirapine (NVP) is a non-nucleoside reverse transcriptase inhibitor (NNRTI) widely used in the treatment of human immunodeficiency virus type 1 (HIV-1) and is the first-choice NNRTI during pregnancy. NVP shows a sex dimorphic profile in humans with sex differences in bioavailability, biotransformation and toxicity. In this study, sex differences in NVP metabolism and inhibition of NVP metabolism by the antidepressant nortriptyline (NT) were evaluated using rats as experimental animals. NVP was administered orally to male and female rats and sex differences in plasma levels and pharmacokinetic parameters were analysed. NVP plasma levels were higher in female compared with male rats, and pharmacokinetic parameters such as maximum plasma concentration (Cmax), time to Cmax (Tmax), half-life (t1/2) and area under the plasma concentration-time curve from the time of dosing to the last measurable concentration (AUClast) showed ca. 4-, 5-, 7- and 22-fold higher values in female rats. In vitro experiments carried out with hepatic microsomes confirmed slower NVP metabolism in female rats, with a maximum velocity (Vmax) 2-fold lower than in male hepatic microsomes. The major metabolite in both sexes was 12-hydroxynevirapine (12-OH-NVP), with the Vmax for this metabolite being 15-fold lower in female compared with male rat hepatic microsomes. Inhibition of NVP metabolism by NT was similar in both sexes, with statistically non-significant differences in 50% inhibitory concentration (IC50) values. In summary, NVP is metabolised more slowly in female compared with male rats, but the inhibitory effect of NT is similar in both sexes.

Pharmacokinetic determination and analysis of nortriptyline based on GC-MS coupled with hollow-fiber drop-to-drop solvent microextraction technique.

AIM: A simple, sensitive and robust technique of hollow-fiber drop-to-drop solvent microextraction coupled with GC-MS has been successfully developed for the detection of antidepressant drug nortriptyline in human blood and urine samples. The recoveries of the drug from the spiked samples are found to be well within the range and appropriate to support the method. RESULTS: The LOD for the drug was obtained to be 0.007, 0.009 and 0.021 µg ml-1 in deionized water, urine and blood samples of human subjects, respectively. Linearity was obtained over the concentration range of 0.5-5.0 mg l-1 in deionized water with correlation coefficient 0.99672.

Mechanistic Physiologically Based Pharmacokinetic (PBPK) Model of the Heart Accounting for Inter-Individual Variability: Development and Performance Verification.

Modern model-based approaches to cardiac safety and efficacy assessment require accurate drug concentration-effect relationship establishment. Thus, knowledge of the active concentration of drugs in heart tissue is desirable along with inter-subject variability influence estimation. To that end, we developed a mechanistic physiologically based pharmacokinetic model of the heart. The models were described with literature-derived parameters and written in R, v.3.4.0. Five parameters were estimated. The model was fitted to amitriptyline and nortriptyline concentrations after an intravenous infusion of amitriptyline. The cardiac model consisted of 5 compartments representing the pericardial fluid, heart extracellular water, and epicardial intracellular, midmyocardial intracellular, and endocardial intracellular fluids. Drug cardiac metabolism, passive diffusion, active efflux, and uptake were included in the model as mechanisms involved in the drug disposition within the heart. The model accounted for inter-individual variability. The estimates of optimized parameters were within physiological ranges. The model performance was verified by simulating 5 clinical studies of amitriptyline intravenous infusion, and the simulated pharmacokinetic profiles agreed with clinical data. The results support the model feasibility. The proposed structure can be tested with the goal of improving the patient-specific model-based cardiac safety assessment and offers a framework for predicting cardiac concentrations of various xenobiotics.

Analysis of the Mechanism of Prolonged Persistence of Drug Interaction between Terbinafine and Amitriptyline or Nortriptyline.

The purpose of the study was to quantitatively estimate and predict drug interactions between terbinafine and tricyclic antidepressants (TCAs), amitriptyline or nortriptyline, based on in vitro studies. Inhibition of TCA-metabolizing activity by terbinafine was investigated using human liver microsomes. Based on the unbound Ki values obtained in vitro and reported pharmacokinetic parameters, a pharmacokinetic model of drug interaction was fitted to the reported plasma concentration profiles of TCAs administered concomitantly with terbinafine to obtain the drug-drug interaction parameters. Then, the model was used to predict nortriptyline plasma concentration with concomitant administration of terbinafine and changes of area under the curve (AUC) of nortriptyline after cessation of terbinafine. The CYP2D6 inhibitory potency of terbinafine was unaffected by preincubation, so the inhibition seems to be reversible. Terbinafine competitively inhibited amitriptyline or nortriptyline E-10-hydroxylation, with unbound Ki values of 13.7 and 12.4 nM, respectively. Observed plasma concentrations of TCAs administered concomitantly with terbinafine were successfully simulated with the drug interaction model using the in vitro parameters. Model-predicted nortriptyline plasma concentration after concomitant nortriptylene/terbinafine administration for two weeks exceeded the toxic level, and drug interaction was predicted to be prolonged; the AUC of nortriptyline was predicted to be increased by 2.5- or 2.0- and 1.5-fold at 0, 3 and 6 months after cessation of terbinafine, respectively. The developed model enables us to quantitatively predict the prolonged drug interaction between terbinafine and TCAs. The model should be helpful for clinical management of terbinafine-CYP2D6 substrate drug interactions, which are difficult to predict due to their time-dependency.

Evaluation of the pharmacokinetics of oral amitriptyline and its active metabolite nortriptyline in fed and fasted Greyhound dogs.

This study reports the pharmacokinetics of oral amitriptyline and its active metabolite nortriptyline in Greyhound dogs. Five healthy Greyhound dogs were enrolled in a randomized crossover design. A single oral dose of amitriptyline hydrochloride (actual mean dose 8.1 per kg) was administered to fasted or fed dogs. Blood samples were collected at predetermined times from 0 to 24 h after administration, and plasma drug concentrations were measured by liquid chromatography with mass spectrometry. Noncompartmental pharmacokinetic analyses were performed. Two dogs in the fasted group vomited following amitriptyline administration and were excluded from analysis. The range of amitriptyline CMAX for the remaining fasted dogs (n = 3) was 22.8-64.5 ng/mL compared to 30.6-127 ng/mL for the fed dogs (n = 5). The range of the amitriptyline AUCINF for the three fasted dogs was 167-720 h·ng/mL compared to 287-1146 h·ng/mL for fed dogs. The relative bioavailability of amitriptyline in fasted dogs compared to fed dogs was 69-91% (n = 3). The exposure of the active metabolite nortriptyline was correlated to amitriptyline exposure (R(2)  = 0.84). Due to pharmacokinetic variability and the small number of dogs completing this study, further studies are needed assessing the impact of feeding on oral amitriptyline pharmacokinetics. Amitriptyline may be more likely to cause vomiting in fasted dogs.

Exploring the role of drug-metabolising enzymes in antidepressant side effects.

RATIONALE: Cytochrome P450 enzymes are important in the metabolism of antidepressants. The highly polymorphic nature of these enzymes has been linked to variability in antidepressant metabolism rates, leading to hope regarding the use of P450 genotyping to guide treatment. However, evidence that P450 genotypic differences underlie the variation in treatment outcomes is inconclusive. OBJECTIVES: We explored the links between both P450 genotype and serum concentrations of antidepressant with antidepressant side effects, using data from the Genome-Based Therapeutic Drugs for Depression Project (GENDEP), which is a large (n = 868), pharmacogenetic study of depressed individuals treated with escitalopram or nortriptyline. METHODS: Patients were genotyped for the enzymes CYP2C19 and CYP2D6, and serum concentrations of both antidepressant and primary metabolite were measured after 8 weeks of treatment. Side effects were assessed weekly. We investigated associations between P450 genotypes, serum concentrations of antidepressants and side effects, as well as the relationship between P450 genotype and study discontinuation. RESULTS: P450 genotype did not predict total side effect burden (nortriptyline: n = 251, p = 0.5638, ß = -0.133, standard error (SE) = 0.229; escitalopram: n = 340, p = 0.9627, ß = -0.004, SE = 0.085), study discontinuation (nortriptyline n = 284, hazard ratio (HR) = 1.300, p = 0.174; escitalopram n = 376, HR = 0.870, p = 0.118) or specific side effects. Serum concentrations of antidepressant were only related to a minority of the specific side effects measured: dry mouth, dizziness and diarrhoea. CONCLUSIONS: In this sample where antidepressant dosage is titrated using clinical judgement, P450 genotypes do not explain differences between patients in side effects with antidepressants. Serum drug concentrations appear to only explain variability in the occurrence of a minority of specific side effects.

Pharmacokinetic interaction between nevirapine and nortriptyline in rats: inhibition of nevirapine metabolism by nortriptyline.

One of the most frequent comorbidities of HIV infection is depression, with a lifetime prevalence of 22 to 45%. Therefore, it was decided to study a potential pharmacokinetic interaction between the nonnucleoside reverse transcriptase inhibitor nevirapine (NVP) and the tricyclic antidepressant nortriptyline (NT). NVP and NT were administered to rats either orally, intraduodenally, or intravenously, and the changes in plasma levels and pharmacokinetic parameters were analyzed. Experiments with rat and human hepatic microsomes were carried out to evaluate the inhibitory effects of NT on NVP metabolism. NVP plasma concentrations were significantly higher when this drug was coadministered with NT. The maximum plasma concentrations of NVP were increased 2 to 5 times and the total plasma clearance was decreased 7-fold in the presence of NT. However, statistically significant differences in the pharmacokinetic parameters of NT in the absence and presence of NVP were not found. In vitro studies with rat and human hepatic microsomes confirmed the inhibition of NVP hepatic metabolism by NT in a concentration-dependent way, with the inhibition being more intense in the case of rat microsomes. In conclusion, a pharmacokinetic interaction between NVP and NT was detected. This interaction was a consequence of the inhibition of hepatic metabolism of NVP by NT. In vivo human studies are required to evaluate the effects of this interaction on the pharmacokinetics of NVP before it can be taken into account for patients receiving NVP.

[Effect of piperine on metablism and distribution of nortriptyline in mice].

OBJECTIVE: To study the pharmacokinetics and brain/plasma concentration ratio of nortriptyline at multiple doses in mice which were pre-treated with physiological saline, piperine and verapamil. METHODS: A total of 216 male Kun Ming mice [(25±3) g] were equally divided into 4 groups randomly. Each group was intragastrically administered physiological saline (B), piperine (170 µg/ kg), piperine (5 mg/kg) and verapamil (5 mg/kg) for 8 days. On the 8th day, 1 h after giving the above drugs, each mice was intraperitoneally injected nortriptyline (13 mg/kg). The mice were sacrificed by picking off eyeballs at the time intervals of 5, 15, 30 min, and 1, 2, 4, 6, 8 and 12 h, and the cerebra were collected and weighted. Nortriptyline in mouse plasma and brain was determined by HPLC-MS/MS. The pharmacokinetic properties of the plasma, brain and brain/plasma were calculated. RESULTS: The AUC0-12 h of brain/plasma concentration ratio in the 170 µg/kg piperine group was significantly lower than that in the other groups (P<0.05), while the AUC0-12 h of brain/plasma concentration ratios in the 5 mg/kg piperine group and the verapamil group were not significantly different from those of untreated mice. CONCLUSION: Piperine (170 µg/kg) may induce P-glycoprotein expression in the blood-brain barrier, while piperines at 5 mg/kg has no influence on P-glycoprotein expression in the bloodbrain barrier.

Norepinephrine transporter occupancy by nortriptyline in patients with depression: a positron emission tomography study with (S,S)-[¹8F]FMeNER-D2.

Norepinephrine transporter (NET) plays important roles in the treatment of various neuropsychiatric disorders, such as depression and attention deficit hyperactivity disorder (ADHD). Nortriptyline is a NET-selective tricyclic antidepressant (TCAs) that has been widely used for the treatment of depression. Previous positron emission tomography (PET) studies have reported over 80% serotonin transporter occupancy with clinical doses of selective serotonin reuptake inhibitors (SSRIs), but there has been no report of NET occupancy in patients treated with relatively NET-selective antidepressants. In the present study, we used PET and (S,S)-[18¹8F]FMeNER-D2 to investigate NET occupancies in the thalamus in 10 patients with major depressive disorder taking various doses of nortriptyline, who were considered to be responders to the treatment. Reference data for the calculation of occupancy were derived from age-matched healthy controls. The result showed approximately 50-70% NET occupancies in the brain as a result of the administration of 75-200 mg/d of nortriptyline. The estimated effective dose (ED50) and concentration (EC50) required to induce 50% occupancy was 65.9 mg/d and 79.8 ng/ml, respectively. Furthermore, as the minimum therapeutic level of plasma nortriptyline for the treatment of depression has been reported to be 70 ng/ml, our data indicate that this plasma nortriptyline concentration corresponds to approximately 50% NET occupancy measured with PET, suggesting that more than 50% of central NET occupancy would be appropriate for the nortriptyline treatment of patients with depression.

Chronic amitriptyline overdose in a child.

Amitriptyline, a tricyclic antidepressant, has a well-described toxicity profile, and acute ingestions are common in the pediatric toxicology world. However, little can be found in the literature regarding chronic overdose. We describe a case of a 6-year-old girl who was prescribed amitriptyline 30 mg nightly for sleep problems, but was mistakenly given 300 mg (15 mg/kg) nightly for over a month. She was noted to have mental status changes and difficulty reading several days after starting the medication. She presented to the local children's hospital in status epilepticus with significant cardiac conduction abnormalities on ECG. Her total amitriptyline/nortriptyline level was found to be 1676 ng/mL (normal therapeutic level 50-300 ng/mL). She was treated for several days with sodium bicarbonate. Within 24 h, her neurologic status improved and had returned to baseline within several days. Her ECG normalized, and she was discharged home, without apparent sequelae. A brief discussion of possible protective mechanisms (including pharmacogenomic) is presented.

Influence of ABCB1 (P-glycoprotein) haplotypes on nortriptyline pharmacokinetics and nortriptyline-induced postural hypotension in healthy volunteers.

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT: A single nucleotide polymorphism in ABCB1, which encodes P-glycoprotein, has retrospectively been associated with symptoms of nortriptyline-induced postural hypotension in depressed patients. This finding needs to be replicated in independent studies before recommendations regarding pharmacogenetic testing can be made. WHAT THIS STUDY ADDS: In a prospective study of healthy volunteers homozygous for ABCB1 (1236-2677-3435, TTT/TTT or CGC/CGC), a single dose of nortriptyline was administered, plasma exposure was determined and blood pressure and heart rate were monitored during posture change. No differences between ABCB1 haplotype groups were found in plasma exposure of nortriptyline and its active metabolites, E- and Z-10-hydroxynortriptyline. The heart rate response to posture change was increased with nortriptyline, whereas there was no difference in blood pressure response. However, no differences between haplotype groups were observed except that the pre dose heart rate response to standing was greater in the TTT than CGC homozygotes. The association between ABCB1 polymorphisms and nortriptyline-induced postural hypotension found in a previous study could not be confirmed. The results raise the possibility of a predisposition in heart rate response in the TTT homozygotes rather than an effect of nortriptyline. AIMS To investigate the influence of ABCB1 (1236-2677-3435) polymorphisms on nortriptyline pharmacokinetics and nortriptyline-induced postural hypotension in healthy volunteers. METHODS: Genetic screening of 67 healthy volunteers identified eight CGC homozygotes and nine TTT homozygotes of ABCB1 (1236-2677-3435), who were administered a single dose of nortriptyline 25 mg. Plasma exposure of nortriptyline and its active metabolites, E- and Z-10-hydroxynortriptyline, was determined over 72 h. Heart rate and blood pressure responses to posture change (active standing and passive head-up tilt) were measured continuously using finger plethysmography. RESULTS: There were no differences in plasma exposure between ABCB1 haplotype groups, as the geometric mean (95% CI) AUC(0,72 h) ratios were 0.98 (0.94, 1.03), 1.02 (0.96, 1.09) and 0.95 (0.80, 1.10) for nortriptyline, E- and Z-10-hydroxynortriptyline, respectively. The pre dose heart rate response to standing was greater in the TTT than CGC homozygotes (mean (95% CI) difference 7.4 (1.5, 13.4) beats min(-1) , P = 0.02). At t(max) at 8 h post dose, nortriptyline increased the heart rate response to posture change in all subjects with mean (95% CI) Δ heart rate values of 7.4 (3.6, 11.3) beats min(-1) on active standing (P = 0.0009) and 4.8 (2.0, 7.6) beats min(-1) on head-up tilt (P = 0.002), but no difference was observed between haplotype groups. There was no difference in blood pressure response to posture change in either group. CONCLUSION: The association between ABCB1 polymorphisms and nortriptyline-induced postural hypotension found in the previous study could not be confirmed. The results raise the possibility of a predisposition in heart rate response in the TTT homozygotes rather than an effect of nortriptyline.

Detection of amitriptyline, citalopram, and metabolites in porcine bones following extended outdoor decomposition.

Skeletal remains of a domestic pig were assessed for relative distribution of amitriptyline, citalopram, and metabolites. Following acute exposure and outdoor decomposition for 2 years, drugs and metabolites were analyzed in 13 different bones. Bones were pulverized following a simple wash procedure, and drugs were extracted by passive incubation in methanol, followed by solid-phase extraction. Samples were analyzed by ultra-high performance liquid chromatography (UHPLC) and confirmed with gas chromatography-mass spectrometry. The Kruskall-Wallis test showed that bone type was a main effect with respect to drug level for all analytes, with levels varying from 33- to 166-fold. Ratios of levels of drug to that of the corresponding metabolite were less variable, varying roughly one- to eightfold. This suggests limitations in the interpretive value of drug measurements in bone and that relative levels of drug and metabolites should be further investigated in terms of forensic value.

Mother-infant antidepressant concentrations, maternal depression, and perinatal events.

OBJECTIVE: The authors explored the relationship of cord-maternal antidepressant concentration ratios and maternal depression with perinatal events and preterm birth. METHOD: The investigators examined 21 mother-infant pairs that had antidepressant exposure during pregnancy. The antidepressants included serotonin reuptake inhibitors (SRIs) and nortriptyline (a norepinephrine inhibitor and mild SRI). The mothers were evaluated with the Structured Clinical Interview for DSM-IV. Depression ratings were repeated at 20, 30, and 36 weeks' pregnancy. At delivery, investigators assessed cord and maternal antidepressant concentrations, neonatal outcomes on the Peripartum Events Scale (PES), and gestational weeks at birth. The investigators performed this study at the Women's Behavioral HealthCARE Program, Western Psychiatric Institute and Clinic, University of Pittsburgh Medical Center, Pennsylvania, from April 2003 until September 2006. RESULTS: Mean ± SD cord-to-maternal concentration ratios were 0.52 ± 0.35 (range, 0.00-1.64) for the parent drug and 0.54 ± 0.17 (range, 0.28-0.79) for the metabolite. Nine of 21 mothers (43%) had a major depressive episode. From examining the maximum depression ratings, the mean ± SD Structured Interview Guide for the Hamilton Depression Rating Scale, Atypical Depression Symptoms Version score was 16.0 ± 7.6. One third (7/21) of infants had at least 1 perinatal event (PES ≥ 1). The frequency of deliveries complicated by any perinatal event was similar in depressed and nondepressed mothers. There was no significant association between perinatal events and cord-to-maternal antidepressant concentration ratios or maternal depression levels. Exposure to short half-life antidepressants compared to fluoxetine resulted in more perinatal events (7/16 = 44% vs 0/5 = 0%; P = .06). Fourteen percent (3/21) of infants were preterm. Preterm birth was not associated with cord-to-maternal metabolite concentration ratios, depression levels, or exposure to fluoxetine. CONCLUSIONS: Antidepressant-exposed infants experienced a limited number of transient perinatal events. No association between cord-maternal concentration ratios or maternal depression and perinatal events could be identified. Contrary to other reports, we detected no increased risk for perinatal events with fluoxetine therapy compared to the short half-life antidepressants. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00279370.

Risk assessment of accidental nortriptyline poisoning: the importance of cytochrome P450 for nortriptyline elimination investigated using a population-based pharmacokinetic simulator.

It is not possible to make a prospective clinical study that reveals the importance of the nortriptyline metabolising cytochrome P450 (CYP) isoforms (CYP1A2, CYP2C19, CYP2D6, and CYP3A4) in relation to attaining potential toxic nortriptyline concentrations with a possibly fatal outcome. Therefore to study this we have applied the population based pharmacokinetic simulator Simcyp. The objective was to estimate how important CYP2C19 and CYP2D6 phenotype status, hepatic activity of CYP3A4, body weight, CYP2D6 phenotype dose adjustment, and drug-drug interactions are with regard to accidental poisoning in a virtual population receiving a daily dose of 100mg nortriptyline. Accidental poisoning is here defined as intake of a normal dose which because of slow metabolism may lead to potentially toxic concentrations. The input parameters values for Simcyp were based on average literature in vitro and in vivo data. The Simcyp simulations of nortriptyline pharmacokinetics reflected reported clinical concentration-time profiles, therapeutic drug monitoring data, and the consequence of CYP2D6 poor metaboliser (PM) and ultrarapid metaboliser status. Of the investigated factors, the simulations indicate that having CYP2D6 PM status is a major risk factor for attaining high concentrations and thereby possibly becoming poisoned by nortriptyline. Of the CYP2D6 PM subjects 16% would attain plasma concentrations exceeding the toxic limit. Individuals with the combination of CYP2D6 PM status and 10% of the average liver CYP3A4 expression had a 90% risk of becoming poisoned. The results point towards the combination of low CYP3A4 activity and CYP2D6 PM status of major importance for attaining possibly toxic nortriptyline concentrations. In a forensic toxicological context, the results indicate that both the activity of CYP3A4, information on possible drug-drug interactions, and the genotype of CYP2D6 are needed in order to elucidate whether an individual might have been accidentally poisoned because of slow metabolism. In a clinical context, the simulations suggest that precise individual dose adjustment of nortriptyline requires information regarding the activity of both CYP3A4 and CYP2D6. This underlines the value of therapeutic drug monitoring for nortriptyline. Population based pharmacokinetic simulations are considered useful tools for risk assessment in clinical and forensic toxicology.

Development and validation of a highly sensitive LC-MS/MS method for simultaneous quantitation of nortriptyline and 10-hydroxynortriptyline in human plasma: application to a human pharmacokinetic study.

A highly sensitive and specific LC-MS/MS method has been developed for simultaneous estimation of nortriptyline (NTP) and 10-hydroxynortriptyline (OH-NTP) in human plasma (250 µL) using carbamazepine as an internal standard (IS). LC-MS/MS was operated under the multiple reaction-monitoring mode using the electrospray ionization technique. A simple liquid-liquid extraction process was used to extract NTP, OH-NTP and IS from human plasma. The total run time was 2.5 min and the elution of NTP, OH-NTP and IS occurred at 1.44, 1.28 and 1.39 min, respectively; this was achieved with a mobile phase consisting of 20 mm ammonium acetate : acetonitrile (20:80, v/v) at a flow rate of 0.50 mL/min on a HyPURITY C(18) column. The developed method was validated in human plasma with a lower limit of quantitation of 1.09 ng/mL for both NTP and OH-NTP. A linear response function was established for the range of concentrations 1.09-30.0 ng/mL (r > 0.998) for both NTP and OH-NTP. The intra- and inter-day precision values for NTP and OH-NTP met the acceptance as per FDA guidelines. NTP and OH-NTP were stable in a battery of stability studies, i.e. bench-top, auto-sampler and freeze-thaw cycles. The developed assay was applied to a pharmacokinetic study in humans.