The electrocardiographic and antiarrhythmic effects of imipramine hydrochloride at therapeutic plasma concentrations

Clinical pharmacology considerations and drug-drug interactions with long-acting cabotegravir and rilpivirine relevant to sub-Saharan Africa

Long-acting injectable (LAI) cabotegravir and rilpivirine for HIV treatment and LAI cabotegravir for pre-exposure HIV prophylaxis are being rolled out in a multitude of countries worldwide. Due to the prolonged exposure, it can be challenging to undertake 'traditional' pharmacokinetic studies and current guidance is derived from their oral equivalents or physiologically based pharmacokinetic studies. This review aims to consider pharmacokinetic characteristics of cabotegravir and rilpivirine and describe anticipated drug-drug interactions (DDIs) with frequent concomitant medications in African settings. Relevant co-medications were identified from the WHO 2021 List of Essential Medicines. All original human and physiologically based pharmacokinetic studies published in English on PubMed, discussing DDIs with LAI cabotegravir and rilpivirine prior to April 2023, were reviewed. The Liverpool HIV interaction database was also reviewed (https://www.hiv-druginteractions.org/checker). LAI cabotegravir and rilpivirine have half-lives of 6-12 and 13-28 weeks, respectively. Cabotegravir is primarily metabolized by UDP-glucuronyltransferase (UGT)-1A1 and rilpivirine by cytochrome P450 (CYP)-3A4. LAI cabotegravir and rilpivirine themselves exhibit low risk of perpetrating interactions with co-medications as they do not induce or inhibit the major drug metabolizing enzymes. However, they are victims of DDIs relating to the induction of their metabolizing enzymes by concomitantly administered medication. Noteworthy contraindicated co-medications include rifamycins, carbamazepine, phenytoin, flucloxacillin and griseofulvin, which induce CYP3A4 and/or UGT1A1, causing clinically significant reduced concentrations of rilpivirine and/or cabotegravir. In addition to virologic failure, subtherapeutic concentrations resulting from DDIs can lead to emergent drug resistance. Clinicians should be aware of potential DDIs and counsel people receiving LAI cabotegravir/rilpivirine appropriately to minimize risk.

The cardiovascular safety of tricyclic antidepressants in overdose and in clinical use

Tricyclic antidepressants (TCAs) remain widely prescribed for depression and many other conditions. There may be important differences between individual TCA in regard to their overdose toxicity and their cardiac toxicity in clinical use. We conducted a systematic review to compare the toxicity of individual TCA in overdose and the risk of serious adverse cardiac events occurring with therapeutic doses. We used the fatal toxicity index (FTI) and case fatality ratio as markers of fatality in overdose, and hazard ratios or odds ratios for the risk of cardiovascular adverse events during normal clinical use. In all, 30 reports of mortality in overdose and 14 observational studies assessing the risk of cardiovascular adverse events in clinical use were included. FTI values were of the same order of magnitude (101-102) for all TCAs except lofepramine. Desipramine appears to be somewhat more likely than other TCAs to lead to death in overdose. Amitriptyline, clomipramine, dothiepin/dosulepin, doxepin, trimipramine and imipramine showed broadly similar toxicity and were usually reported to be less toxic than desipramine. Data on nortriptyline were contradictory. Lofepramine had the lowest risk of death in overdose. The rank order of overdose toxicity was broadly consistent between different FTI definitions and between markers used. With respect to the risk of cardiovascular events at clinically relevant exposure, amitriptyline, nortriptyline and lofepramine were associated with a greater risk of in-use cardiotoxicity. All measures of overdose toxicity were subject to external influences and confounding. The continued use of TCAs in depression and other conditions should be minimized when considering their undoubted toxicity in overdose and possible toxicity in normal clinical use.

Management Strategies for Nocturia

PURPOSE OF REVIEW

Nocturia is defined as awakening due to the desire to void during a period of intended sleep. The pathophysiology of nocturia is multifactorial and management remains a challenge. Herein, we provide an overview of the management strategies for nocturia and summarize the existing evidence for treatment of nocturia across the condition's broad etiologic categories: nocturnal polyuria, diminished bladder capacity, and global polyuria.

RECENT FINDINGS

Treatment should begin with behavioral modification. A high level of evidence supports the efficacy of desmopressin in the treatment of nocturnal polyuria. Data supporting the efficacy of α-blockers, antimuscarinics, and surgical bladder outlet procedures in the treatment of nocturia remains limited. Treatment options for nocturia are determined by underlying mechanism. Desmopressin is effective in treating nocturnal polyuria. Surgical intervention, α-blockers, and antimuscarinics may improve nocturia when associated with lower urinary tract symptoms or overactive bladder in the setting of diminished bladder capacity.

Association Between Depression, Anxiety, and Antidepressant Use With T-Wave Amplitude and QT-Interval

Objectives: Cardiac repolarization may be affected by psychiatric disorders and/or antidepressant use, but evidence for this is inconclusive. This study examined the relationship between depressive and anxiety disorder and use of antidepressants with T-wave amplitude (TWA) and QT-interval.

Methods: Data was obtained from the Netherlands Study of Depression and Anxiety (n = 1,383). Depression/anxiety was diagnosed with the DSM-IV based Composite International Diagnostic Interview. The use of tricyclic antidepressants (TCAs), selective serotonin and noradrenalin reuptake inhibitors (SNRIs), and selective serotonin reuptake inhibitors (SSRIs) was established. T-wave amplitude and QT-interval corrected for heart rate (QTc) were obtained from an ECG measured in a type II axis configuration.

Results: Compared to controls, persons with depression or anxiety disorders did not show a significantly different TWA (p = 0.58; Cohen's d = 0.046) or QTc (p = 0.48; Cohen's d = −0.057). In spite of known sympathomimetic effects, TCA use (p = 0.26; Cohen's d = −0.162) and SNRI use (p = 0.70; Cohen's d = −0.055) were not significantly associated with a lower TWA. TCA use (p = 0.12; Cohen's d = 0.225) and SNRI use (p = 0.11; Cohen's d = 0.227) were also not significantly associated with a prolonged QTc.

Conclusion: We did not find evidence that either depressive/anxiety disorder or antidepressant use is associated with abnormalities in TWA or QTc. Earlier found sympathomimetic effects of TCAs and SNRIs are not evident in these measures of cardiac repolarization.

Detachment of surface membrane invagination systems by cationic amphiphilic drugs

Several cell types develop extensive plasma membrane invaginations to serve a specific physiological function. For example, the megakaryocyte demarcation membrane system (DMS) provides a membrane reserve for platelet production and muscle transverse (T) tubules facilitate excitation:contraction coupling. Using impermeant fluorescent indicators, capacitance measurements and electron microscopy, we show that multiple cationic amphiphilic drugs (CADs) cause complete separation of the DMS from the surface membrane in rat megakaryocytes. This includes the calmodulin inhibitor W-7, the phospholipase-C inhibitor U73122, and anti-psychotic phenothiazines. CADs also caused loss of T tubules in rat cardiac ventricular myocytes and the open canalicular system of human platelets. Anionic amphiphiles, U73343 (a less electrophilic U73122 analogue) and a range of kinase inhibitors were without effect on the DMS. CADs are known to accumulate in the inner leaflet of the cell membrane where they bind to anionic lipids, especially PI(4,5)P2. We therefore propose that surface detachment of membrane invaginations results from an ability of CADs to interfere with PI(4,5)P2 interactions with cytoskeletal or BAR domain proteins. This establishes a detubulating action of a large class of pharmaceutical compounds.

Prevalence of QTc interval changes in acute psychiatric care: a cross-sectional study

INTRODUCTION

In a case series we examined the prevalence and incidence of QT changes during a 1-week interval in hospitalized patients in a general psychiatry ward during a 6-month period.

METHOD

This cross-sectional study was done on electrocardiographic QT interval of patients admitted to the Psychiatric Department of Taleghani Hospital during a 6-month period excluding subjects with underlying cause of QT prolongation.

RESULTS

Admission and follow-up electrocardiograms of 27 men and 47 women were studied, there was significant QT prolongation during hospitalization (P value 0.001) in approximately 30% of subjects, irrespective of type of administered medication.

CONCLUSION

Pro-arrhythmic changes as reflected in QTc prolongation and QTc dispersion in electrocardiograms are common in patients admitted in psychiatric wards irrespective of type of therapy and should be screened and followed by serial electrocardiograms to minimize untoward cardiac outcomes.

Desipramine prevents cardiac gap junction uncoupling

BACKGROUND AND PURPOSE

Uncoupling of cardiac gap junction channels is an important arrhythmogenic mechanism in ischemia/reperfusion. Antiarrhythmic peptide AAP10 (H-Gly-Ala-Gly-Hyp-Pro-Tyr-CONH(2)) has been shown to prevent acidosis-induced uncoupling and ischemia-related increase in dispersion. Previous structure-effect investigations and subsequent computer modeling studies indicated that the tricyclic antidepressant desipramine may exert similar effects as AAP10.

METHODS

We assessed the binding of (14)C-AAP10 to membranes of rabbit cardiac ventricles and its displacement with desipramine in a classical radioligand binding and competition study. Gap junction currents were measured between isolated pairs of human atrial cardiomyocytes under normal and acidotic (pH 6.3) conditions with or without 1 μmol/l desipramine using dual whole-cell voltage clamp. The effect of 1 μmol/l desipramine was assessed in isolated rabbit hearts (Langendorff technique) undergoing local ischemia by coronary occlusion with 256-channel electrophysiological mapping and subsequent analysis of connexin43 (Cx43) expression, phosphorylation (Western blot), and subcellular localization (immunohistology).

RESULTS

We found saturable (14)C-AAP10 binding to cardiac membranes (K (D), 0.29 ± 0.11 nmol/l; B (max), 42.5 ± 7.2 pmol/mg) which could be displaced by desipramine with a K (D.High) = 0.14 μmol/l and a K (D.Low) = 22 μmol/l. Acidosis reduced the gap junction conductance in human cardiomyocyte pairs from 24.1 ± 4.7 to 11.5 ± 2.5 nS, which could be significantly reversed by desipramine (26.6 ± 4.8 nS). In isolated hearts, ischemia resulted in significantly increased dispersion of activation-recovery intervals, loss of membrane Cx43, and dephosphorylation of Cx43, which all could be prevented by desipramine.

CONCLUSION

Desipramine seems to prevent the uncoupling of cardiac gap junctions and ischemia-related increase in dispersion.

Cardiologic side effects of psychotropic drugs

Psychotropic drugs can produce cardiovascular side effects associated with a degree of cardiotoxicity. The coexistence of a heart disease complicates the management of mental illness, can contribute to a reduced quality of life and a worse illness course. The co-occurrence of psychiatric disorders in cardiac patients might affect the clinical outcome and morbidity. Moreover, the complex underlying mechanism that links these two conditions remains unclear. This paper discusses the known cardiovascular complications of psychotropic drugs and analyzes the important implications of antidepressive treatment in patients with previous cardiac history.

Antidepressant drugs and cardiovascular pathology: a clinical overview of effectiveness and safety

OBJECTIVE

To review data examining the relationships between depression, antidepressants and cardiovascular disease.

METHOD

Structured searches of PubMed, Medline and Embase conducted in March 2008.

RESULTS

Depression and cardiovascular disease are closely associated clinical entities. Depression appears both to cause and worsen cardiovascular disease. Cardiovascular disease is in turn associated with a high incidence of depression. Depression is associated with increased mortality in cardiovascular disease, and after myocardial infarction (MI) and stroke. Many antidepressants have cardiotoxic properties. Tricyclic drugs are highly cardiotoxic in overdose and may induce cardiovascular disease and worsen outcome in established cardiovascular disease. Reboxetine, duloxetine and venlafaxine are known to increase blood pressure. Other antidepressants have neutral or beneficial effects in various cardiovascular disorders.

CONCLUSION

Sertraline, fluoxetine, citalopram, bupropion and mirtazapine appear to be safe to use after MI; the use of sertraline, and response to citalopram and mirtazapine may improve mortality. Paroxetine and citalopram appear to be safe to use in patients with established coronary artery disease. Limited data suggest that a variety of antidepressants are effective and safe to use after stroke.

An evaluation of the cardiovascular safety profile of duloxetine: findings from 42 placebo-controlled studies

BACKGROUND AND OBJECTIVE

In recent years, new classes of medication, such as the serotonin-noradrenaline reuptake inhibitors (SNRIs), have been developed for use in the treatment of major depressive disorder (MDD). For many years, treatment options were largely limited to the use of monoamine oxidase inhibitors (MAOIs), tricyclic antidepressants (TCAs) and selective serotonin reuptake inhibitors (SSRIs). However, there have been published reports of orthostatic hypotension, arrhythmias and corrected QT (QTc) interval changes in patients treated with TCAs. As new medications become available, it is important to understand how their cardiovascular safety profile compares with that of more established agents to aid clinicians and patients in choosing the best treatment options. This study was designed to evaluate the cardiovascular safety profile of the SNRI duloxetine through evaluation of cardiovascular-related parameters and adverse events (AEs).

METHODS

The cardiovascular safety of duloxetine was assessed using all placebo-controlled duloxetine clinical trial data as of December 2005. This consisted of data from 42 placebo-controlled clinical trials of 8504 patients who were treated with duloxetine. Additional information from a high-dose clinical pharmacology study and postmarketing safety surveillance are also presented. Of the placebo-controlled trials included in this analysis, clinical indications under investigation included MDD (15 studies), diabetic peripheral neuropathic pain (3 studies), fibromyalgia (2 studies), generalised anxiety disorder (3 studies) and lower urinary tract disorders (19 studies, all related to incontinence). Cardiovascular safety was evaluated based on vital signs, ECGs and the incidence of treatment-emergent AEs potentially related to cardiovascular safety. These safety parameters were analysed across all indications. To identify both serious and non-serious cardiovascular-related AEs, as well as AEs reported as the reason for discontinuation, a comprehensive list of terms derived from the Medical Dictionary for Regulatory Activities (version 8.0) was generated and used to search the duloxetine databases for cardiovascular-related events.

RESULTS

Calculation of change from baseline to maximum in ECG parameters showed significant differences between treatment groups for all parameters, with decreases from baseline in RR, QRS and QT intervals for patients receiving duloxetine and increases from baseline for patients treated with placebo. These shifts were related to small heart rate changes, but the mean differences were not considered clinically relevant. Categorical analyses of shifts from normal to abnormal (or abnormal to normal) for heart rate and QT corrected for heart rate using Fridericia's formula (QTcF) values showed that most patients did not shift from their baseline category. Patients with MDD who were treated for up to 1 year with duloxetine had blood pressure changes early in treatment that then stabilised. Even in patients with elevated blood pressure at baseline in these clinical trials, no increased risk of sustained blood pressure elevation with duloxetine treatment was found.

CONCLUSION

Overall, the findings presented here support our conclusions that use of duloxetine does not appear to be associated with significant cardiovascular risks in patients with conditions for which the drug has been approved or studied.

Analysis of electrocardiographic data following use of paroxetine in pediatric depression and obsessive-compulsive disorder

OBJECTIVE

This retrospective analysis of electrocardiographic (ECG) data investigated the cardiovascular effects of paroxetine 10-50 mg/day in pediatric patients (7-18 years of age). Data were collected from three 8- to 10-week, randomized, placebo-controlled, double-blind trials of paroxetine in pediatric patients with major depressive disorder or obsessive-compulsive disorder.

METHOD

Electrocardiograms (ECGs) were retrospectively retrieved from 63 study sites in the United States and Canada. Only patients with at least one screening and one on-treatment ECG were included. ECGs were analyzed for heart rate, QT interval corrected using Bazett's formula (QTcB) and Fridericia's formula (QTcF), at screening and while being treated. PR, R-R, and QRS intervals and the maximum change in QTcB and QTcF from screening to endpoint were determined. Clinically significant thresholds were defined a priori.

RESULTS

A total of 1,451 ECGs from 449 patients receiving placebo (n = 207), paroxetine (n = 200), or imipramine (n = 42) were analyzed. Treatment with paroxetine did not significantly increase QTcB or QTcF or any ECG parameters compared with placebo. Treatment with imipramine significantly increased heart rate and QTcB, R-R, and QRS intervals compared with either paroxetine or placebo.

CONCLUSIONS

Data from this retrospective study indicate that paroxetine (10-50 mg/day) is unlikely to be associated with significant ECG changes in medically healthy pediatric patients.

QTc prolongation associated with combination therapy of levofloxacin, imipramine, and fluoxetine

OBJECTIVE

To report QTc interval prolongation associated with combination therapy including levofloxacin, imipramine, and fluoxetine.

CASE SUMMARY

A 49-year-old white female presented to the emergency department with fever, aches, and pains for the past 3 days. She was diagnosed and treated for pyelonephritis in the hospital. Therapy included intravenous levofloxacin 500 mg every 24 hours and ceftriaxone 2 g every 24 hours, along with her medications upon admission, including imipramine 50 mg at bedtime and fluoxetine 10 mg/day. She was discharged after 5 days and returned the next day with chest tightness and shortness of breath. Upon the second admission, a 12-lead electrocardiogram showed a QTc interval of 509 msec. Levofloxacin was discontinued and the QTc interval fell to 403 msec. The patient was discharged 3 days later and instructed to consult with her primary care physician about discontinuing imipramine.

DISCUSSION

This adverse drug reaction is thought to be a pharmacodynamic additive effect among fluoxetine, imipramine, and levofloxacin. Fluoxetine is a potent inhibitor of CYP2D6, and imipramine is metabolized by CYP2D6. Therefore, fluoxetine is able to increase the plasma concentrations of imipramine, leading to QT interval prolongation. Taken with imipramine, levofloxacin can lead to even greater prolongation of the QT interval. Based on the Naranjo probability scale, levofloxacin was possibly associated with cardiac arrhythmias in our patient.

CONCLUSIONS

The use of levofloxacin alone, or more often in concomitant therapy with other medications that are known to prolong the QT interval, may cause QT interval prolongation; however, additional studies/case reports are needed to validate this conclusion.

Knowledge deficits related to the QT interval could affect patient safety

BACKGROUND

Recently, some QT-prolonging, noncardiac medications were withdrawn from the U.S. drug market because of continued inappropriate use by health care practitioners despite warnings and label changes from both the drug manufacturers and the U.S. Food and Drug Administration. This led us to assess the health care practitioners' knowledge of the QT interval and medications that may prolong it.

METHODS

We surveyed health care practitioners, primarily specialists in cardiology, to identify knowledge deficits related to the QT interval.

RESULTS

From a total of 334 survey respondents, 157 (47%) were physicians; 271 (81%) stated that cardiology was their area of specialization. Most of the respondents (86%) said that they would check an ECG before and after starting QT-prolonging medications, but less than half (42%) of all respondents and only 60% of physician respondents were able to accurately measure a sample QT interval on the survey. Less than two-thirds (63%) of respondents were able to accurately identify possible QT-prolonging medications, while only about half (51%) could accurately identify medication combinations that might prolong the QT interval.

CONCLUSIONS

We identified significant knowledge deficits regarding the QT interval and QT-prolonging medications. Additional research is needed to determine the extent to which these knowledge deficits may negatively affect patient safety. We must also develop effective strategies to eliminate these deficits.

Effect of citalopram on ouabain-induced arrhythmia in isolated guinea-pig atria

The effect of citalopram (CTP) a selective serotonin reuptake inhibitor agent was studied on ouabain-induced arrhythmia in spontaneously beating isolated guinea-pig atria. CTP (2-32 microg/ml) produced a dose-dependent decrease in the force of contractions (7-62%), and in the rate of contractions (11-72%). Pre-administration of the atria with CTP inhibited the ouabain-induced arrhythmia in isolated atria. Ouabain alone (1.2 microg/ml) produced arrhythmia at 4.5 min, and asystole at 20.7 min. Pretreatment with CTP (8 microg/ml) significantly increased the time of onset of arrhythmia to 9.5 min. In addition CTP prolonged the beating of atria (survival time) to more than 56 min, and inhibited the occurrence of asystole. These findings indicate that CTP produces direct cardiac action, probably due to the inhibition of cardiac Na(+) and Ca(2+) channels. Moreover our results suggest that CTP may reduce the membrane conductance through inhibition of ionic channels which decrease ouabain-induced arrhythmia.

Psychotropic drugs, cardiac arrhythmia, and sudden death

A variety of drugs targeted towards the central nervous system are associated with cardiac side effects, some of which are linked with reports of arrhythmia and sudden death. Some psychotropic drugs, particularly tricyclic antidepressants (TCAs) and antipsychotic agents, are correlated with iatrogenic prolongation of the QT interval of the electrocardiogram (ECG). In turn, this is associated with the arrhythmia (TdP). This review discusses the association between psychotropic agents, arrhythmia and sudden death and, focusing on TCAs and antipsychotics, considers their range of cellular actions on the heart; potentially pro-arrhythmic interactions between psychotropic and other medications are also considered. At the cellular level TCAs, such as imipramine and amitriptyline, and antipsychotics, such as thioridazine, are associated with inhibition of potassium channels encoded by In many cases this cellular action correlates with ECG changes and a risk of TdP. However, not all psychotropic agents that inhibit HERG at the cellular level are associated equally with QT prolongation in patients, and the potential for QT prolongation is not always equally correlated with TdP. Differences in risk between classes of psychotropic drugs, and between individual drugs within a class, may result from additional cellular effects of particular agents, which may influence the consequent effects of inhibition of repolarizing potassium current.

Effect of fluoxetine and imipramine on the pharmacokinetics and tolerability of the antipsychotic quetiapine

The effects of fluoxetine and imipramine on the pharmacokinetics and nonpsychiatric side effect profile of quetiapine fumarate were investigated in 26 patients with schizophrenia, schizoaffective disorder, or bipolar disorder in a multicenter, two-period, multiple-dose, open-label, randomized trial. Over a 1- to 2-week period, patients were titrated to a 300-mg twice-daily dose of quetiapine. Patients treated for at least 7 days at the target dose entered a combination therapy period, receiving fluoxetine (60 mg daily) or imipramine (75 mg twice daily) for 8 days. Key assessments included pharmacokinetic analysis of quetiapine, the Udvalg for kliniske undersøgelser (UKU) Side Effect Rating Scale, and safety evaluations (e.g., adverse events, electrocardiograms, laboratory tests, and vital signs). Fluoxetine increased the quetiapine area under the plasma concentration time curve during a 12-hour interval (+12%), maximum plasma concentration during the dosing interval (C(ss)(max); +26%), and minimum plasma concentration at the end of the dosing interval (+8%), although it decreased oral clearance (-11%). The change in C(ss)(max) was statistically although not clinically significant. Imipramine did not affect the pharmacokinetics of quetiapine. Overall, scores on the UKU Side Effect Rating Scale improved during combination therapy with either agent, and no statistically significant deterioration was observed for any item. For safety assessments, the only clinically remarkable event was an imipramine-associated complete left bundle branch block in one patient. No unexpected side effects were reported. In conclusion, combination therapy with quetiapine and fluoxetine or imipramine had a minimal effect on quetiapine pharmacokinetics and was well tolerated.

Serum levels and cardiovascular effects of tricyclic antidepressants and selective serotonin reuptake inhibitors in depressed patients

Tricyclic antidepressants (TCAs) and selective serotonin reuptake inhibitors (SSRIs) are used to treat depression. Whereas cardiovascular effects have occasionally been reported during controlled studies with SSRIs, TCA treatment poses a well-known problem in this respect. To investigate the putative correlation between antidepressant dose or serum levels and adverse effects, the authors devised a naturalistic study to evaluate the tricyclic antidepressants' and SSRIs' effect on the cardiovascular system. The authors also compared antidepressant serum levels to adverse effects. Inpatients treated with TCAs or SSRIs were included; an electrocardiogram (ECG) and a Schellong test were carried out on the day patients entered the hospital and during steady-state treatment with antidepressant drugs when blood was drawn for therapeutic drug monitoring. The patient population consisted of 114 acutely depressed patients; 81 patients were treated with TCAs and 33 with SSRIs. The TCAs comprised amitriptyline (n = 43), clomipramine (n = 11), doxepin (n = 19) and imipramine (n = 8); the SSRIs comprised fluvoxamine (n = 14) and paroxetine (n = 19). In TCA-treated patients, the authors observed the same type of abnormalities in conduction and orthostatic hypotension as had been observed earlier. The authors also observed cases of first-degree atrioventricular block, prolonged QTc interval, and orthostatic hypotension in SSRI-treated patients. Thus SSRIs also appear to affect the cardiovascular system, which might pose a problem for patients with preexisting conduction disease. The authors observed a strong correlation between the decrease in systolic pressure and antidepressant serum concentration (except for clomipramine and paroxetine), suggesting that antidepressant serum level is a better correlate than dose.

Drug interactions with cisapride: clinical implications

Cisapride, a prokinetic agent, has been used for the treatment of a number of gastrointestinal disorders, particularly gastro-oesophageal reflux disease in adults and children. Since 1993, 341 cases of ventricular arrhythmias, including 80 deaths, have been reported to the US Food and Drug Administration. Marketing of the drug has now been discontinued in the US; however, it is still available under a limited-access protocol. Knowledge of the risk factors for cisapride-associated arrhythmias will be essential for its continued use in those patients who meet the eligibility criteria. This review summarises the published literature on the pharmacokinetic and pharmacodynamic interactions of cisapride with concomitantly administered drugs, providing clinicians with practical recommendations for avoiding these potentially fatal events. Pharmacokinetic interactions with cisapride involve inhibition of cytochrome P450 (CYP) 3A4, the primary mode of elimination of cisapride, thereby increasing plasma concentrations of the drug. The macrolide antibacterials clarithromycin, erythromycin and troleandomycin are inhibitors of CYP3A4 and should not be used in conjunction with cisapride. Azithromycin is an alternative. Similarly, azole antifungal agents such as fluconazole, itraconazole and ketoconazole are CYP3A4 inhibitors and their concomitant use with cisapride should be avoided. Of the antidepressants nefazodone and fluvoxamine should be avoided with cisapride. Data with fluoxetine is controversial, we favour the avoidance of its use. Citalopram, paroxetine and sertraline are alternatives. The HIV protease inhibitors amprenavir, indinavir, nelfinavir, ritonavir and saquinavir inhibit CYP3A4. Clinical experience with cisapride is lacking but avoidance with all protease inhibitors is recommended, although saquinavir is thought to have clinically insignificant effects on CYP3A4. Delavirdine is also a CYP3A4 inhibitor and should be avoided with cisapride. We also recommend avoiding coadministration of cisapride with amiodarone, cimetidine (alternatives are famotidine, nizatidine, ranitidine or one of the proton pump inhibitors), diltiazem and verapamil (the dihydropyridine calcium antagonists are alternatives), grapefruit juice, isoniazid, metronidazole, quinine, quinupristin/dalfopristin and zileuton (montelukast is an alternative). Pharmacodynamic interactions with cisapride involve drugs that have the potential to have additive effects on the QT interval. We do not recommend use of cisapride with class Ia and III antiarrhythmic drugs or with adenosine, bepridil, cyclobenzaprine, droperidol, haloperidol, nifedipine (immediate release), phenothiazine antipsychotics, tricyclic and tetracyclic antidepressants or vasopressin. Vigilance is advised if anthracyclines, cotrimoxazole (trimethoprim-sulfamethoxazole), enflurane, halothane, isoflurane, pentamidine or probucol are used with cisapride. In addition, uncorrected electrolyte disturbances induced by diuretics may increase the risk of torsade de pointes. Patients receiving cisapride should be promptly treated for electrolyte disturbances.

Blockade of the HERG human cardiac K(+) channel by the antidepressant drug amitriptyline

1. Amitriptyline has been known to induce QT prolongation and torsades de pointes which causes sudden death. We studied the effects of amitriptyline on the human ether-a-go-go-related gene (HERG) channel expressed in Xenopus oocytes and on the rapidly activating delayed rectifier K(+) current (I(Kr)) in rat atrial myocytes. 2. The amplitudes of steady-state currents and tail currents of HERG were decreased by amitriptyline dose-dependently. The decrease became more pronounced at more positive potential, suggesting that the block of HERG by amitriptyline is voltage dependent. IC(50) for amitriptyline block of HERG current was progressively decreased according to depolarization: IC(50) values at -30, -10, +10 and +30 mV were 23.0, 8.71, 5.96 and 4.66 microM, respectively. 3. Block of HERG by amitriptyline was use dependent: exhibiting a much faster block at higher activation frequency. Subsequent decrease in frequency after high activation frequency resulted in a partial relief of HERG blockade. 4. Steady-state block by amitriptyline was obtained while depolarization to +20 mV for 0.5 s was applied at 0.5 Hz: IC(50) was 3.26 microM in 2 mM [K(+)](o). It was increased to 4. 78 microM in 4 mM [K(+)](o), suggesting that the affinity of amitriptyline on HERG was decreased by external K(+). 5. In rat atrial myocytes bathed in 35 degrees C, 5 microM amitriptyline blocked I(Kr) by 55%. However, transient outward K(+) current (I(to)) was not significantly affected. 6. In summary, the data suggest that the block of HERG currents may contribute to arrhythmogenic side effects of amitriptyline.

QTc-interval abnormalities and psychotropic drug therapy in psychiatric patients

BACKGROUND

Sudden unexplained death in psychiatric patients may be due to drug-induced arrhythmia, of which lengthening of the rate-corrected QT interval (QTc) on the electrocardiogram is a predictive marker. We estimated the point prevalence of QTc lengthening in psychiatric patients and the effects of various psychotropic drugs.

METHODS

Electrocardiograms were obtained from 101 healthy reference individuals and 495 psychiatric patients in various inpatient and community settings and were analysed with a previously validated digitiser technique. Patients with and without QTc lengthening, QTc dispersion, and T-wave abnormality were compared by logistic regression to calculate odds ratios for predictive variables.

FINDINGS

Abnormal QTc was defined from the healthy reference group as more than 456 ms and was present in 8% (40 of 495) of patients. Age over 65 years (odds ratio 3.0 [95% CI 1.1-8.3]), use of tricyclic antidepressants (4.4 [1.6-12.1]), thioridazine (5.4 [2.0-13.7]), and droperidol (6.7 [1.8-24.8]) were robust predictors of QTc lengthening, as was antipsychotic dose (high dose 5.3 [1.2-24.4]; very high dose 8.2 [1.5-43.6]). Abnormal QT dispersion or T-wave abnormalities were not significantly associated with antipsychotic treatment, but were associated with lithium therapy.

INTERPRETATION

Antipsychotic drugs cause QTc lengthening in a dose-related manner. Risks are substantially higher for thioridazine and droperidol. These drugs may therefore confer an increased risk of drug-induced arrhythmia.

Imipramine does not affect argon-laser-induced pin-prick pain thresholds and laser-evoked cerebral potentials

The tricyclic antidepressant imipramine has shown analgesic effect in human clinical and experimental pain studies. The aim of the present study was to test the effect of imipramine on a pure short-term nociceptive stimulus with pin-prick pain quality. In a randomized, placebo-controlled, double-blind, crossover study, the hypoalgesic effect of a single oral dose of 100 mg imipramine was investigated in 10 healthy volunteers. Test procedures performed before and 2, 4, 6, 8, 10, 12 and 14 h after medication included determination of warmth and pin-prick pain thresholds to high-energy argon laser light stimulation on the hand, as well as laser-evoked cerebral potentials to suprathreshold stimulation. Both the warmth and the pin-prick pain thresholds (p=0.49 and 0.85) and the root mean square of the laser-evoked potentials (p=0.89) were unaltered by imipramine. It is concluded that a single oral dose of 100 mg imipramine has no effect on pin-prick pain. This study demonstrates the important fact that a drug may show clear analgesic effect in some experimental pain models while it is without effect in other models; e.g. imipramine is known to affect pain tolerance and summation thresholds. Pre-clinical tests of potentially analgesic drugs should therefore be based on different pain-stimulation modalities. Copyright 1998 European Federation of Chapters of the International Association for the Study of Pain.

Cardiac electrophysiological effects of citalopram in guinea pig papillary muscle comparison with clomipramine

The effect of citalopram, a selective serotonin reuptake inhibitor (SSRI) antidepressant, was studied on cardiac action potential configuration and compared with that of the tricyclic antidepressant (TCA) clomipramine. Conventional microelectrode techniques were used in right ventricular papillary muscle preparations of the guinea pig. Citalopram caused a concentration-dependent (10-100 microM) shortening of action potential duration (APD), depression of plateau and overshoot potential, and reduction of maximum velocity of depolarization (V(max)). No significant changes in resting membrane potential were observed. Similar results were obtained with clomipramine; however, reduction of V(max) and overshoot was more pronounced with clomipramine, whereas citalopram caused relatively greater shortening of APD. Effects of both drugs were partly reversible. The results indicate that the SSRI antidepressant citalopram, similarly to TCA compounds, alters cardiac action potential configuration in guinea pig ventricular muscle, probably owing to inhibition of cardiac Na(+) and Ca(2+) channels. Differences in cardiac side effects of the two drugs may be related to their different actions on cardiac action potential configuration.

Serotonin reuptake inhibitor, fluoxetine, dilates isolated skeletal muscle arterioles. Possible role of altered Ca2+ sensitivity

1. Inhibitors of serotonin reuptake in the central nervous system, such as fluoxetine, may also affect the function of vascular tissues. Thus, we investigated the effect of fluoxetine on the vasomotor responses of isolated, pressurized arterioles of rat gracilis muscle (98 +/- 4 microns in diameter at 80 mmHg perfusion pressure). 2. We have found that increasing concentrations of fluoxetine dilated arterioles up to 155 +/- 5 microns with an EC50 of 2.5 +/- 0.5 x 10(-6) M. 3. Removal of the endothelium, application of 4-aminopyridine (4-AP, an inhibitor of aminopyridine sensitive K+ channels), or use of glibenclamide (an inhibitor of ATP-sensitive K+ channels) did not affect the vasodilator response to fluoxetine. 4. In the presence of 10(-6), 2 x 10(-6) or 10(-5) M fluoxetine noradrenaline (NA, 10(-9)-10(-5) M) and 5-hydroxytryptamine (5-HT, 10(-9)-10(-5)M)-induced constrictions were significantly attenuated resulting in concentration-dependent parallel rightward shifts of their dose-response curves (pA2 = 6.1 +/- 0.1 and 6.9 +/- 0.1, respectively). 5. Increasing concentrations of Ca2+ (10(-4) 3 x 10(-2) M) elicited arteriolar constrictions (up to approximately 30%), which were markedly reduced by 2 x 10(-6)M fluoxetine, whereas 10(-5)M fluoxetine practically abolished these responses. 6. In conclusion, fluoxetine, elicits substantial dilations of isolated skeletal muscle arterioles, a response which is not mediated by 4-AP- and ATP-sensitive K+ channels or endothelium-derived dilator factors. The findings that fluoxetine had a greater inhibitory effect on Ca2+ elicited constrictions than on responses to NA and 5-HT suggest that fluoxetine may inhibit Ca2+ channel(s) or interfere with the signal transduction by Ca2+ in the vascular smooth muscle cells.

Electrocardiographic effects of fluoxetine and doxepin in patients with major depressive disorder

Cardiovascular adverse effects are amongst the most serious observed with antidepressant drugs and are often due to effects on cardiac conduction and refractoriness. However, such electrophysiologic effects may not be evident when using conventional electrocardiographic measures. Forty patients with major depressive disorder (according to DSM-III-R criteria) were enrolled in a 6-week double-blind parallel group study of fluoxetine (N = 20) or doxepin (N = 20). Cardiac conduction (QRS duration) and repolarization (corrected QT interval, QTc), were measured using signal-averaged electrocardiograms and 12-lead electrocardiogram at baseline and after 2, 4, and 6 weeks of treatment. Patients taking doxepin (mean daily dosage at 6 weeks 169 +/- 42 mg) were similar to those taking fluoxetine (37 +/- 18 mg) for demographic variables and improvement in depression scores but volunteered more side effects (p = 0.011), especially dry mouth (p < 0.001) and dizziness/lightheadedness (p = 0.005). After 6 weeks, doxepin increased heart rate (69 +/- 12 to 81 +/- 13 beats per minute; p = 0.0003) and prolonged QTc (from 417 +/- 36 to 439 +/- 28 msec; p < 0.03); overall QRS duration was not prolonged but was correlated with serum doxepin concentrations (r = 0.78, p < 0.0001). Fluoxetine had no effect on QTc (428 +/- 24 msec at baseline vs. 430 +/- 24 msec at 6 weeks) or QRS duration (97 +/- 12 msec at baseline vs. 94 +/- 12 msec at 6 weeks). The standard 12-lead electrocardiogram showed no significant change in QRS or QTc for either drug. Using a sensitive measure of electrocardiographic effects, doxepin prolongs repolarization and may slow cardiac conduction. Fluoxetine has no measurable electrocardiographic effects, which suggests an increased safety margin for cardiac adverse effects. The ability of the signal-averaged electrocardiogram to resolve small changes in the electrocardiogram is useful in the assessment of drugs with subtle electrophysiologic effects.

Abnormal ventricular repolarization mimicking myocardial infarction after heterocyclic antidepressant overdose

In 2 young adult women who experienced acute heterocyclic antidepressant intoxication, we found a quite unusual electrocardiographic pattern characterized by abnormal ST-tract elevation in the right precordial leads associated with a marked QRS widening (right bundle branch block and left anterior fascicular block type). Because serum electrolyte imbalance and acute myocardial ischemic events were excluded, the mechanism by which antidepressant overdose may produce such elevation of the ST tract remains unclear.

Cardiovascular effects of therapeutic doses of tricyclic antidepressants in children and adolescents

OBJECTIVE

Tricyclic antidepressants (TCAs) play an important role in the treatment of pediatric psychiatric disorders. Despite widespread clinical use, concerns about their possible cardiovascular risk have arisen following several published reports of sudden death associated with their use in children. Accordingly, available evidence concerning TCA-associated cardiovascular effects in children and adolescents was surveyed.

METHOD

A systematic literature search from 1967 to 1996 identified relevant pediatric studies that evaluated cardiovascular effects of TCAs.

RESULTS

Twenty-four studies involving 730 children and adolescents given imipramine, amitriptyline, desipramine, or nortriptyline were found. TCA treatment was associated with minor increases in systolic and diastolic blood pressure, in heart rate, and in the electrocardiographic (ECG) conduction parameters, PR, QRS, and QTc. Holter ECG monitoring and exercise testing also revealed minor treatment effects. Some ECG changes related to specific TCAs emerged. Few age-related ECG differences in TCA-treated children, adolescents, or adults were detected. Associations of ECG abnormalities and relatively higher serum TCA levels were found.

CONCLUSION

TCA treatment in children and adolescents, like that in adults, is associated with cardiovascular changes of uncertain, but probably minor, clinical significance. More information is needed on the contribution of other physiological conditions on the cardiovascular system during exposure to TCAs. Guidelines for using TCAs in children and adolescents are presented.

Electrocardiographic changes during desipramine and clomipramine treatment in children and adolescents

OBJECTIVE

With the increased use of tricyclic antidepressants in children, and several reports of several sudden deaths associated with desipramine (DMI) treatment, systematic study of their cardiac effects is indicated. In the present study, DMI's and clomipramine's (CMI) short-term effects on the electrocardiogram (ECG) were compared, as well as the long-term effects of CMI.

METHOD

The ECGs of 47 children and adolescents in treatment trials were examined at baseline, after 5 weeks of CMI and of DMI treatment, and during CMI maintenance (mean duration 24.6 months).

RESULTS

At 5 weeks of CMI and of DMI treatment, the heart rate, PR, QRS, and QT-corrected (QTc) intervals on ECG were significantly increased from baseline (p < .05); DMI increased PR and QRS intervals more than CMI (p < .05), and CMI increased QTc more (p < .05). Tachycardia was the most common change (36%). More patients experienced an incomplete intraventricular conduction delay during DMI treatment (23%, 9/39) than during CMI (2%, 1/47) (p < .05). Four patients (9%) acutely developed a prolonged QTc during either DMI or CMI. Long-term maintenance ECGs during CMI treatment (n = 25) were not significantly different from that at week 5, although some individuals developed or resolved specific ECG changes.

CONCLUSION

CMI and DMI both produced ECG changes typically reported for tricyclic antidepressants, and they differed on specific ECG changes. Changes in ECG measures for individuals from short to long term suggest that continued monitoring is required.

Effects of desipramine on autonomic control of the heart

OBJECTIVE

To assess the effects of desipramine (DMI) on autonomic control of the heart.

METHODS

Blood pressure, RR interval (the time between successive heart beats), and RR interval variability, a noninvasive measure of autonomic control of the heart, were assessed in 13 subjects younger than 30 years old.

RESULTS

DMI treatment was associated with an increase in blood pressure, a decrease in RR interval, and a decline in low and high frequency RR interval variability.

CONCLUSIONS

These preliminary data suggest that, in young people, DMI treatment produces a substantial decrease in parasympathetic input to the heart and an increase in the ratio of sympathetic to parasympathetic input, changes that in certain circumstances have been associated with an increased risk of arrhythmia. In exploring the cardiac effects of the tricyclic antidepressants (TCAs) in young people, the impact of TCAs on autonomic input to the heart should be examined.

A comparison of seven antiarrhythmic drugs in patients with ventricular tachyarrhythmias. Electrophysiologic Study versus Electrocardiographic Monitoring Investigators

BACKGROUND

The relative efficacies of various antiarrhythmic drugs in the treatment of ventricular tachyarrhythmias are not well known. This study examined the effectiveness of imipramine, mexiletine, pirmenol, procainamide, propafenone, quinidine, and sotalol in patients with ventricular tachyarrhythmias who were enrolled in the Electrophysiologic Study versus Electrocardiographic Monitoring trial.

METHODS

Patients were randomly assigned to undergo serial testing of the efficacy of the seven antiarrhythmic drugs by one of two strategies: electrophysiologic study or Holter monitoring together with exercise testing. The seven drugs were then tested for efficacy in random order in patients who were eligible to receive them. The frequencies of predictions of drug efficacy and of adverse drug effects during the initial drug titration were tabulated for all 486 randomized subjects. Patients received long-term treatment with the first antiarrhythmic drug that was predicted to be effective on the basis of drug testing. Recurrences of arrhythmia, deaths, and adverse drug effects during long-term follow-up were recorded for the 296 patients in whom an antiarrhythmic drug was predicted to be effective.

RESULTS

In the electrophysiologic-study group, the percentage of patients who had predictions of drug efficacy was higher with sotalol (35 percent) than with the other drugs (16 percent, P < 0.001). There was no significant difference among the drugs in the Holter-monitoring group. The percentage of patients with adverse drug effects was lowest among those receiving sotalol. The actuarial probability of a recurrence of arrhythmia after a prediction of drug efficacy by either strategy was significantly lower for patients treated with sotalol than for patients treated with the other drugs (risk ratio, 0.43; 95 percent confidence interval, 0.29 to 0.62; P < 0.001). With sotalol, as compared with the other drugs combined, there were lower risks of death from any cause (risk ratio, 0.50; 95 percent confidence interval, 0.30 to 0.80; P = 0.004), death from cardiac causes, (0.50; P = 0.02), and death from arrhythmia (0.50; P = 0.04). The cumulative percentage of patients in whom a drug was predicted to be effective and in whom it remained effective and tolerated was higher for sotalol than for the other drugs (P < 0.001).

CONCLUSIONS

Sotalol was more effective than the other six antiarrhythmic drugs in preventing death and recurrences of arrhythmia. In patients similar to those in this study, if antiarrhythmic-drug therapy is to be used to prevent recurrences of ventricular tachyarrhythmias, treatment with sotalol and assessment of its potential efficacy by Holter monitoring are a reasonable initial strategy.

Centpropazine affinity to cortical noradrenergic receptors and effect on their responsiveness in the rat

We have studied the in-vitro effect of centpropazine on cerebral cortical noradrenergic receptors measured as the accumulation of second messengers, cyclic AMP and inositol phosphate, stimulated by noradrenaline, and the binding to alpha 1- and beta-adrenoceptors. Centpropazine inhibited inositol phosphate, but not the cyclic AMP accumulation in the cerebral cortical slices of the rat. It moderately antagonized the specific binding of [3H]prazosin, but did not affect the specific binding of the beta-adrenoceptor ligand, [3H]CGP 12177, to cerebral cortical membranes.

Lack of effect of mianserin on the symptoms of diabetic neuropathy

The effect of the non-tricyclic antidepressant mianserin on symptoms of diabetic neuropathy has been studied in 18 patients in a double-blind, cross-over study with imipramine as a positive control. The patients were treated with placebo, mianserin, and imipramine, each for two weeks, in randomized order, with 1-3 weeks between the treatments. The symptoms were assessed by observer and self-rating scales. Mianserin was given in the fixed dosage of 60 mg per day, whereas the dose of imipramine was adjusted to yield the optimal plasma concentration of imipramine plus desipramine of 400-600 nmol.l-1. The mianserin plus desmethylmianserin plasma concentration ranged from 85 to 850 nmol.l-1, with the highest concentration in a patient who was a poor metabolizer of both sparteine and mephenytoin. The symptoms of neuropathy were significantly reduced during imipramine treatment, although somewhat less than in earlier studies. In contrast, mianserin produced no change in symptoms in comparison with placebo. As there was no evidence that higher mianserin (plus metabolite) steady-state concentrations were associated with a more favourable effect, the negative outcome appeared not to be related to underdosing with mianserin. In contrast to drugs with documented effects on the symptoms of diabetic neuropathy, mianserin has a very weak or no inhibitory effect on 5-HT and noradrenaline reuptake and this may explain its poor clinical effect.

Drug treatment of depression in medically ill patients

Depressive symptoms are common in medically ill patients although depressive disorders are considerably underdiagnosed and undertreated. Drug treatments for depression are reviewed in terms of a risk/benefit analysis. The main benefit is approximately to double the chance of recovery (from about 30 to 65%), with possible associated improvements in physical condition. The risks of treatment are considerable and include overdose, unwanted effects at therapeutic dose and interaction with other drugs. Among the risks associated with specific medical conditions are orthostatic hypotension, cardiotoxicity, deterioration of seizure control in epileptic patients and increased side effects in patients with renal and hepatic impairment. The available data suggest that there is relatively little to choose between antidepressants in terms of efficacy (although the quantity and quality of these data vary). It is therefore primarily the risks which should determine the choice of antidepressant, and these must be separately evaluated for each patient.

Effects of alprazolam and imipramine on parasympathetic cardiac control in patients with generalized anxiety disorder

A noninvasive measure was used to assess the effects of alprazolam, imipramine and placebo on parasympathetic (vagal) cardiac control following 6-weeks of medication in patients with generalized anxiety disorder. Flexible dosage at therapeutic levels resulted in increased heart rate and blood pressure and in decreased cardiac vagal control in patients receiving imipramine but not alprazolam or placebo. About 50% of the variance in heart rate changes and changes in mean arterial blood pressure following treatment with imipramine could be accounted for by changes in cardiac vagal control. Decreased cardiac vagal control can now be added to the list of cardiovascular changes seen following several weeks of treatment with imipramine.

Response of depression to very high plasma levels of imipramine plus desipramine

Forty-five depressed patients were treated with imipramine for 6 weeks. Seven of 7 patients (100%) who had plasma levels of imipramine plus desipramine greater than 500 ng/ml showed a 50% or greater improvement in Hamilton depression scores compared with 23 of 38 patients (60%) with plasma levels less than 500 ng/ml (p less than 0.057).

Tricyclic antidepressant poisoning

OBJECTIVE

To review poisoning with tricyclic antidepressants.

DATA SOURCE

English language literature search using Australian Medlars Service (1977-1989), manual search of journals and review of bibliographies in identified articles.

STUDY SELECTION

Approximately 250 articles, abstracts and book chapters were selected for analysis.

DATA EXTRACTION

The literature was reviewed and 93 articles were selected as representative of important advances.

DATA SYNTHESIS

The major features of overdose are neurological, cardiac, respiratory and anticholinergic. Life-threatening complications develop within six hours of overdose or not at all. All patients seen within six hours of overdose should have their stomachs emptied. All patients should receive activated charcoal. Coma, convulsions, respiratory depression and hypotension are treated with standard resuscitation techniques and drugs. Treat patients with significant cardiotoxicity or cardiac arrest with alkalinisation by sodium bicarbonate or hyperventilation, aiming for an arterial pH of 7.45-7.55. Lignocaine is used for ventricular arrhythmias. Other antiarrhythmic drugs are contraindicated (Class 1A, Class 1C), potentially lethal (Class II), of no benefit (phenytoin) or of unproven efficacy (Class III and Class IV). Physostigmine has no role at all. Haemodialysis and haemoperfusion are of no benefit.

CONCLUSION

The death rate of those who reach hospital is 2%-3%. Most of these deaths are cardiac in origin, and are caused by direct depression of myocardial function rather than cardiac arrhythmias.

Drug-induced supraventricular tachycardia: a case report of fluoxetine

We report the occurrence of supraventricular tachycardia and hypotension in a 54-year-old woman after maintenance therapy with fluoxetine. Although cases of tachycardia and palpitations have been reported, supraventricular tachycardia and hypotension have not been directly attributed to fluoxetine.

Pediatric cardiovascular effects of imipramine and desipramine

Electrocardiograms were evaluated in 39 children and adolescents before and after the clinical use of imipramine and desipramine. The average increase in PR interval was 0.01 seconds. The PR interval increased by 0.02 seconds in 11 subjects, and a new first-degree atrioventricular block developed in two subjects. These changes were not related to the choice between imipramine and desipramine, the dose, or the method of administration. An increase in PR interval by 0.02 seconds or more did correlate with having an abnormality disclosed on a pretreatment electrocardiogram. The average increase in PR interval was 0.007 seconds for subjects with normal baseline electrocardiograms and 0.019 seconds for subjects with conduction and nonconduction abnormalities disclosed in baseline tracings. None of the electrocardiogram changes resulted in adverse clinical consequences.

Treatment effects of alprazolam and imipramine: physiological versus subjective changes in patients with generalized anxiety disorder

The correspondence between changes in physiological activity and somatic symptom reports was assessed in generalized anxiety disorder patients treated with alprazolam or imipramine. After 6 weeks, the two medications produced comparable reductions in self-reported somatic symptoms. However, patients taking alprazolam showed decreases in systolic blood pressure, epinephrine, and norepinephrine, and patients taking imipramine showed increases in heart rate, blood pressure, electromyographic activity, and norepinephrine. Thus, though the physiological changes associated with alprazolam treatment were consistent with changes in symptom reports, treatment with imipramine produced a desynchrony: patients reported significant decreases in cardiovascular symptoms and muscle tension in spite of the fact that heart rate, blood pressure, and electromyographic activity increased. Possible explanations for this counterintuitive phenomenon are discussed.