Cardiac complications of tricyclic antidepressant therapy

Cardiac effects of tricyclic antidepressant medication. A preliminary study of nortriptyline

Systolic time intervals and drug plasma concentrations have been measured in a group of patients receiving repeated treatment with nortriptyline. Significant positive correlations between plasma nortriptyline levels and prolongation of pre-ejection phase (P less than 0.005)) and increase in the ratio pre-ejection phase, left ventricular ejection time (P less than 0.05) were obtained. A deterioration in cardiac function, with increase in heart rate, resulting in a negative inotropic effect has been shown to occur with therapeutic doses of nortriptyline. The potential dangers of tricyclic antidepressant drugs on the heart in patients whose myocardium is already compromised or those who accumulate high plasma concentrations are emphasised.

Acute cardiovascular toxicity of trazodone, etoperidone and imipramine in rats

The cardiovascular effects of trazodone, a broad-spectrum antidepressant and its analogue etoperidone, were compared with imipramine, following intravenous infusion in rats. Their effects on electrocardiogram and blood pressure were simultaneously recorded until cardiac arrest. Hypotension was the primary effect of trazodone and etoperidone. ECG changes, i.e. lengthening of the PR interval, were observed only when the blood pressure reached very low values. On the other hand, imipramine produced first the well known ECG changes and then a drop in blood pressure. As far as mortality was concerned, trazodone was the least toxic drug, followed by etoperidone, whereas imipramine was most toxic; these differences being in agreement with the LD50 values reported in rats by the i.v. route. It is concluded that trazodone and etoperidone produce in rats cardiovascular effects, which are different from those of imipramine. Moreover these differences are consistent with their pharmacological properties, particularly their interaction with catecholamines, which are inhibited by trazodone or etoperidone and potentiated by imipramine.

Plasma concentrations and cardiotoxic effects of desipramine and protriptyline in the rat

1 Desipramine and protriptyline were administered to anaesthetized rats by two consecutive intravenous infusions in order to obtain a peak level (first infusion) followed by lower steady state concentrations (second infusion) (Wagner, 1974). Theoretical plasma level time courses were confirmed experimentally.2 Desipramine and protriptyline were measured in atria and ventricles. Increasing infusion rates led to proportional increases in plasma and atrial concentrations. The tissue/medium ratio ranged from 57 to 21 for desipramine and from 43 to 11 for protriptyline according to the time of determination during infusions.3 Heart rate changes, deviation of the electrical axis of the heart and prolongation of atrioventricular conduction were recorded at fixed times during infusion.4 Positive chronotropic effects were noted at plasma concentrations ranging from 0.035 to 0.1 mug/ml for desipramine and from 0.04 to 1.2 mug/ml for protriptyline. At higher plasma concentrations the positive chronotropic effect decreased and bradycardia developed. Both drugs induced right rotation of the electrical axis of the heart. Threshold plasma levels giving 40 degrees rotation were 1.35 mug/ml (desipramine) and 1.75 mug/ml (protriptyline). Atrioventricular conduction was prolonged at threshold plasma concentrations of 2.2 mug/ml for desipramine and 3.6 mug/ml for protriptyline.5 Desipramine is more cardiotoxic than protriptyline. This difference is discussed in relation to the plasma and heart concentration of the two drugs.

A comparison in rabbit isolated hearts of the dysrhythmogenic potential of amitriptyline, maprotiline and mianserin in relation to their ability to block noradrenaline uptake

1. In isolated hearts of rabbits, perfusion with (-)-noradrenaline (0.0059 to 5.9 micronM) resulted in chronotropic and inotropic responses and a shortening of the interval between peak atrial and peak ventricular tensions (the A-V contraction interval). No dysrhythmias developed but at higher concentrations (590 micronM) 2 out of 7 hearts developed dysrhythmias (extrasystoles). 2. Perfusion with the antidepressants amitriptyline or maprotiline (4.8 micronM) or mianserin (28.8 micronM) reduced ventricular force, did not change heart rate and only amitriptyline reduced atrial force and lengthened the A-V contraction interval. At 4.8 micronM mianserin produced only a marginal shortening of the A-V contraction interval. 3. At these concentrations no dysrhythmias developed but at higher concentrations (amitriptyline 8 micronM, maprotiline 8 micronM, mianserin 60 micronM) all the agents produced dysrhythmias involving an interference with atrio-ventricular synchronization. 4. In the presence of mianserin (4.8 micronM) perfusion with noradrenaline (0.0059 to 5.9 micronM) shortened the A-V contraction interval and did not produce dysrhythmias. In the presence of amitriptyline or maprotiline (4.8 micronM) or mianserin (28.8 micronM) the A-V contraction interval generally lengthened and most hearts developed dysrhythmias (usually involving interference with atrio-ventricular synchronization). 5. [3H]-(-)-Noradrenaline uptake in perfused rabbit hearts and in mouse isolated atria or vasa deferentia was inhibited by the antidepressants to a similar extent, amitriptyline being marginally most potent (molar potency taken as 1.0), maprotiline being less potent (1.5) and mianserin least potent (2.0)). 6. It is concluded that of these three antidepressants, mianserin is least cardiotoxic in this preparation and that the ability of these antidepressants to predispose to noradrenaline-induced dysrhythmias is not related to blockade of noradrenaline uptake.

Reversal by physostigmine of clozapine-induced delirium

Clozapine, a new antipsychotic drug without extrapyramidal side effects and with strong sedating potency, can produce acute symptoms of central anticholinergic toxicity. The authors report that physostigmine, a reversible anticholinesterase agent, which can pass the blood-brain barrier, was effective in reversing the clozapine-induced brain syndrome in two patients. Physostigmine also reduced one patient's tachycardia.

Electrocardiographic changes and cardiac arrhythmias in patients receiving psychotropic drugs

Eight patients had cardiac manifestations that were life-threatening in five while taking psychotropic drugs, either phenothiazines or tricyclic antidepressants. Although most patients were receiving several drugs, Mellaril (thioridazine) appeared to be responsible for five cases of ventricular tachycardia, one of which was fatal in a 35 year old woman. Supraventricular tachycardia developed in one patient receiving Thorazine (chlorpromazine). Aventyl (nortriptyline) and Elavil (amitriptyline) each produced left bundle branch block in a 73 year old woman. Electrocardiographic T and U wave abnormalities were present in most patients. The ventricular arrhythmias responded to intravenous administration of lidocaine and to direct current electric shock; ventricular pacing was required in some instances and intravenous administration of propranolol combined with ventricular pacing in one. The tachyarrhythmias generally subsided within 48 hours after administration of the drugs was stopped. Five of the eight patients were 50 years of age or younger; only one clearly had antecedent heart disease. Major cardiac arrhythmias are a potential hazard in patients without heart disease who are receiving customary therapeutic doses of psychotropic drugs. A prospective clinical trial is suggested to quantify the risk of cardiac complications to patients receiving phenothiazines or tricyclic antidepressant drugs.

The effect of amitriptyline on forearm blood flow

The local effect of intra-arterial infusion of amitriptyline (AT) on forearm blood flow was studied in seven healthy subjects. AT was infused at rates of 0.05, 0.10, 0.15, and 0.20 mg-min--1 for periods of 5 min. Forearm blood flow showed a dose-dependent increase when the dose exeeded 0.10 mg-min--1. On the highest dose level the blood flow increased on an average by 73%. No systemic effects, as reflected by changes in heart rate, blood pressure, and blood flow in the contralateral forearm, were observed during the infusion. The present data indicate a dilatating effect of AT on resistance vessels possibly mediated by an alpha-adrenergic blockade.

Combination drug therapy in psychopharmacology

The frequency with which a psychotropic agent is used in combination with another drug preparation is emphasized. The authors present an update of the clinical and theoretical knowledge bearing on combination drug therapy in psychopharmacology. Drug combination interactions that enhance clinical efficacy and those that either diminish it or even endanger the patient are described. The authors hope to create an awareness on the part of physicians of the importance of being knowledgeable in the area of combination drug therapy. Any unexpected or unusual drug action should be examined for the possibility of a drug combination interaction.

Tricyclic antidepressive poisoning with special reference to cardiac complications

Sixty-eight cases of tricyclic antidepressive (TCA) poisoning are discussed. Cardiac arrest occurred in 8 patients, preceded by minor ECG-abnormalities. Five patients died. All cardiac arrests arose within the first 24 h after TCA ingestion. Fifty-seven patients developed ECG-abnormalities, of which 84% began within the first 6 h after TCA ingestion. ECG-abnormalities and other symptoms (respiratory arrest, coma, convulsion and hypotension) often occurred in the same patients. Treatment is described, and cardiac monitoring for at least the first 24 h is recommended. In cases of severe cardiac (ECG) abnormalities, monitoring is recommended until no ECG abnormalities are observed for at least 12 h. In conclusion, the unrestricted use of TCA is cautioned against, since TCA must be regarded as potentially cardiotoxic.