Trazodone and imipramine: comparative effects on canine cardiac conduction

The cardiovascular effects of antidepressants

This monograph comprises a review of the cardiovascular effects of the various types of antidepressant drugs in clinical use. The frequency, severity and clinical importance of these effects are placed in perspective. Most antidepressants can cause changes in blood pressure. Both the tricyclic type (TCA) and the monoamine oxidase inhibitors (MAOIs) can produce postural hypotension which may be dose-limiting. In addition, the MAOIs may be associated with severe hypertension when amine-containing foods or medicines are ingested. It is unlikely that therapeutic doses of any available antidepressant drug could impair cardiac contractility. Typical TCAs can cause abnormalities of cardiac conduction and arrhythmias, but this affects less than 5% of patients, mostly to a clinically insignificant extent. Newer compounds such as lofepramine, mianserin, trazodone and viloxazine seem safer in this respect. Reports of an association between therapeutic use of TCAs and sudden death are far from convincing. Overdosage with the MAOIs, lithium and carbamazepine is dangerous but not common; overdose with a TCA is a major source of morbidity and mortality. Lofepramine, mianserin and trazodone are relatively safe in overdose. The use of various antidepressants in patients with hypertension, cardiac failure, angina pectoris, myocardial infarction, or cardiac arrhythmias is discussed and guidelines suggested for the selection and use of antidepressant medication.

Antidepressant drugs: imipramine, mianserin and trazodone

The advent of newer antidepressant drugs (second generation) during the past two decades has provided an alternative to the use of tricyclic antidepressants in the alleviation of depression. These antidepressants have not been proven to be superior in the therapy of depression to the tricyclic antidepressants but they have been reported to cause fewer cardiac effects. Most of the reported adverse cardiac reactions elicited by antidepressant drugs are based on observations from clinical studies. The possible underlying mechanisms by which these adverse reactions arise have for the large part been proposed on the basis of clinical findings which have been extrapolated back to the known pharmacological actions of such drugs. There is a paucity of hard experimental data in this respect.

Comparative beta-blocking activities and electrophysiologic actions of racemic sotalol and its optical isomers in anesthetized dogs

The relative activities of d-, 1- and racemic-sotalol were studied in two series of anesthetized dogs. Estimates of relative beta-adrenergic blocking potency were based upon the ability of the compounds to antagonize isoproterenol-elicited increases in heart rate and decreases in diastolic blood pressure. On a molar basis, d-sotalol displayed 1/12-1/14th and 1-sotalol 1.6-3.2 X the potency of the racemic parent drug as beta-antagonists. His bundle electrogram (HBE) measurements, surface ECG recordings and the extra stimulus technique at a constant pacing cycle length were utilized to assess the comparative effects of sotalol and its optical isomers on cardiac conduction and refractoriness. At i.v. doses spanning equiactive beta-blocking levels, d- (1, 4, 16 mg X kg-1), 1- (0.25, 1, 4 mg X kg-1) or dl-sotalol (0.5, 2, 8 mg X kg-1) caused dose-dependent increases in ventricular and, to an even greater extent, atrial refractoriness. The mean plasma drug concentrations (Cp) attained with these doses were: d-sotalol 9.5, 44 and 267 nmol X l-1; 1-sotalol 9.6, 16 and 66 nmol X l-1; and dl-sotalol 5.4, 23 and 106 nmol X l-1. The relative mg potency from greatest to least was 1-sotalol greater than dl-sotalol greater than d-sotalol in prolonging the ventricular effective refractory period (V-ERP); the mean increases above control at the highest dose of each were 58 +/- 4, 47 +/- 6 and 38 +/- 3 ms, respectively. At those same dose levels, atrial refractoriness (A-ERP) was maximally elevated 49 +/- 11, 82 +/- 5 and 104 +/- 10 ms by 1-, dl- and d-sotalol, respectively. These increases in refractoriness occurred without alterations in atrial, His-Purkinje or ventricular conduction velocity; however, all three forms of sotalol significantly reduced AV nodal conduction. At the dose multiples studied, the effects on this variable (AH interval) were greatest following 1-sotalol (20-60 ms) or racemic sotalol (20-57 ms) and least following the d-isomer (7-43 ms). The profile of effects observed with d-sotalol is that of an agent with Class III electrophysiologic effects and weak beta-adrenergic blocking properties.

Differential dosing of trazodone in elderly depressed patients: a study to investigate optimal dosing

We investigated the comparative efficacy and tolerance of two initial starting doses of trazodone in 20 elderly inpatients suffering from depressive illness. The first 2-week phase was double-blind. Patients received either 25 mg trazodone tds or 50 mg tds. After this time the study was open, the dose of trazodone being titrated from the initial starting dose to maximise efficacy and tolerance. Patients received study medication for a total of 6 weeks. Assessments for efficacy included the Hamilton Depression rating scale, Zung anxiety scale, visual analogue scales for depression, euphoria and tension, and global assessments of severity and improvement of condition. Tolerance was assessed by means of a checklist of symptoms and adverse effects. Assessments were performed at base line and at weekly or bi-weekly intervals thereafter. A total of 18 patients were included in the analysis. The Zung and visual analogue scales indicated significant superiority for the high-dose group at Week 2. The Hamilton ratings indicated significant superiority for the high-dose group at Week 6 with a strong trend in favour of the high dose group at Week 2. Measures of severity of illness and improvement indicated more rapid improvement over time in the high-dose group. The treatment was generally well tolerated and at no time did adverse events outweigh therapeutic benefit. The incidence of headache and nausea was more frequent in the high-dose group in the first 2 weeks. The group of elderly patients studied benefited from trazodone therapy initiated at a higher therapeutic dose. This dose (150 mg total daily) was well tolerated and proved effective over the course of 6 weeks' treatment.

Management of poisoning associated with "newer" antidepressant agents

Overdose of tricyclic antidepressants remains one of the most difficult poisonings to manage optimally in the emergency department, primarily due to the extremely rapid onset of life-threatening symptomatology. The continued high incidence of such overdoses has ensured that morbidity and mortality rates also remain unacceptably high. The development of the "second-generation antidepressants," with apparently different pharmacology and toxicity after overdose, has been an attempt to address this serious medical problem. This report reviews the published literature on the overdose toxicology of the newer cyclic antidepressants currently available in the United States--amoxapine, maprotiline, and trazodone. Nomifensine, released by the FDA in 1984, recently has been voluntarily withdrawn from the world market. Bupropion, released in 1985, also has been voluntarily withdrawn by the manufacturer three months after its release.

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

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

Second generation antidepressants: a comparative review

The authors review four "second generation" antidepressants (maprotiline, amoxapine, trazodone, and nomifensine) in terms of action on biogenic amines and receptors, antidepressive efficacy, and adverse effects. Doxepin is used as a comparative agent and is similar to the prototypical tricyclic agents in all the above categories. Maprotiline is a selective noradrenergic agent, but shares a similar adverse effect profile with doxepin and may be associated with a high frequency of seizures in overdose. Amoxapine is a mixed action antidepressant with significant neuroleptic activity in vivo. Its adverse effect profile is highlighted by symptoms related to its neuroleptic activity, and seizures and acute renal failure in overdose. Trazodone is a selective serotonergic agent with low anticholinergic activity, and minimal morbidity/mortality in overdose. Reports of priapism, leading to impotence in some men, however, is of concern. Nomifensine is a potent noradrenergic and dopaminergic agent with low anticholinergic activity, and minimum cardiotoxicity and low morbidity/mortality in overdose. Its most important adverse effects include overstimulation and infrequent, usually reversible, immunologic hypersensitivity reactions. Trazodone and nomifensine have favorable profiles for use in the elderly. Trazodone may be more favorable in the anxious/agitated patient due to its sedative effects, whereas nomifensine may be more beneficial in the retarded, apathetic patient.

Electrophysiological and haemodynamic changes with trazodone, amitriptyline and placebo in depressed out-patients

Fourteen out-patients with major depressive disorder completed a double-blind, randomized, parallel group study using trazodone (n = 6), amitriptyline (n = 5) and matching placebo (n = 3). The average daily doses used were 223 mg and 95.3 mg for trazodone and amitriptyline, respectively, over the 28-day treatment period. Cardiovascular function was monitored with high speed ECG and by determining systolic time intervals. No significant effects of either drug on supine or standing blood pressure were demonstrated. Trazodone increased QTc on Day 1 only, and reduced heart rate and increased the PR interval on Day 15; these effects had disappeared by Day 29. Amitriptyline markedly increased heart rate, PR interval and QTc, and reduced T wave amplitude on Days 15 and 29. Trazodone had no consistent effect on systolic time intervals except to increase the LVET index, whereas amitriptyline increased both PEP index and PEP/LVET ratio on Days 15 and 29. It is concluded that amitriptyline had a much more marked effect on cardiac function than did trazodone.

Trazodone overdose

Trazodone did not appear to be a potent respiratory depressant or cardiotoxic or neurotoxic agent in our cases. Further experience is needed to determine a recommended treatment procedure. It is not clear whether the experience with these two cases can be extrapolated to elderly patients, patients with serious physical illnesses, or cases involving larger ingestions. Additional information is required concerning concurrent ingestion of trazodone and alcohol or other CNS-depressant drugs. It would appear that standard treatment including emptying of the stomach, activated charcoal and cathartic, and close observation to monitor and support the respiratory and cardiovascular systems is appropriate. These two case reports suggest that trazodone lacks the serious toxicity encountered with other antidepressant compounds when taken in large overdoses.

A placebo controlled study of the cardiovascular effects of fluvoxamine and clovoxamine in human volunteers

1 Fluvoxamine and clovoxamine, two new potential antidepressants were given to 27 healthy male volunteers in a double-blind, placebo controlled, three-way crossover study. 2 Neither compound affected the electrical intervals of 24 h ambulant electrocardiographic monitoring with the exception of a small increase in R-R interval. 3 There were no changes in blood pressure measurements. 4 The only notable unwanted symptom was nausea for both fluvoxamine and clovoxamine.

Trazodone hydrochloride: a wide spectrum antidepressant with a unique pharmacological profile. A review of its neurochemical effects, pharmacology, clinical efficacy, and toxicology

Trazodone is a new antidepressant agent that was recently introduced in the United States. It has a unique pharmacological profile that is not typical of either tricyclic or monoamine oxidase inhibitor antidepressants. As such it represents a new class of antidepressant drugs. The efficacy of trazodone has been clearly established in comparative studies with imipramine and amitriptyline. Major depression is the principal indication for its use, but good results have been shown in a wide variety of depressive subtypes. Of particular importance is the low frequency of adverse reactions seen with this drug.

Trazodone (Desyrel, Mead-Johnson Pharmaceutical Division)

Trazodone is the first triazolopyridine derivative to be used clinically for the treatment of depression. It has been shown to be equal in efficacy to the tricyclic antidepressants imipramine, desipramine, and amitriptyline in the treatment of major depressive episodes. Researchers have indicated that trazodone exceeds other antidepressants in relieving anxiety, but further study is needed to confirm this effect. Trazodone has been used successfully to relieve depression in schizophrenic patients without worsening their psychotic symptoms. Trazodone blocks serotonin reuptake into presynaptic neurons with little effect on norepinephrine or dopamine. It is rapidly absorbed orally and reaches peak serum levels within two hours. Trazodone is excreted primarily as metabolites by the kidneys and possesses a biphasic elimination half-life of 4.4 hours for the first 10 hours and 7.5 hours for the next 24 hours. Trazodone 200 mg is equal to imipramine 100 mg, and the therapeutic dosage range is 200-600 mg/d. Side effects are infrequent with trazodone; its anticholinergic activity is minimal. Trazodone appears to produce less cardiovascular toxicity than tricyclic antidepressants. To date, reports of fatal overdoses are rare. Trazodone equals available antidepressant drugs in clinical efficacy, and, because it has fewer cardiovascular and anticholinergic side effects, it should prove beneficial in the treatment of depression.