Heart arrhythmia tricyclic antidepressants

Some of the tricyclic antidepressants also have the ability to block serotonin 2A receptors, which may contribute to the therapeutic actions of those agents with this property. Blockade of serotonin 2A receptors is discussed in Chapter 7. Tricyclic antidepressants also block sodium channels in the heart and brain, which can cause cardiac arrhythmias and cardiac arrest in overdose, as well as seizures. 

Adverse effects include constipation, dry mouth and insonmia which occur in > 10% of users. Less commonly, nausea, tachycardia, palpitations, raised blood pressure, anxiety, sweating and altered taste may occur. Blood pressure should be monitored closely throughout its use (twice weekly in the first 3 months). Contraindications include severe h3q>er-tension, peripheral occlusive arterial or coronary heart disease, cardiac arrhythmia, prostatic hypertrophy and those with severe hepatic or renal impairment. It should not be used to treat obesity of endocrine origin or those with a history of major eating disorder or psychiatric disease. Concomitant use with tricyclic antidepressants should be avoided (CNS toxicity). 

CBZ should be used with caution in patients with a history of congestive heart failure or cardiac arrhythmias (because it may aggravate them) and with a history of hematologic reactions to other drugs or hypersensitivity to tricyclic antidepressants. Blood levels should be monitored in patients with renal or hepatic impairment. 

Epinephrine usually Is administered slowly by Intravenous (IV) Injection to relieve acute asthmatic attacks not controlled by other treatments. Intravenous Injection produces an Immediate response. Use of EPI with drugs that enhance cardiac arrhythmias (digitalis or quinidine) Is not recommended. Tricyclic antidepressants and MAO Inhibitors will potentiate the effects of EPI on the heart. Epinephrine should be used with caution In Individuals suffering from hyperthyroidism, cardiovascular disease, hypertension, or diabetes. Adverse effects Include palpitations, tachycardia, sweating, nausea and vomiting, respiratory difficulty, dizziness, tremor, apprehension, and anxiety. 

The cardiotoxic effects of the tricyclic antidepressants have continued to arouse concern particularly in overdose patients, the elderly and in children. In a series of 153 oases with overdose (1 ) 42% had prolongation of the QRS wave that was correlated in degree with dose intake < patients died with arrhythmias of nodal or ventricular origin. Another study (2 ) confirmed an association in 15 patients between plasma levels of drug and QRS duration that reverted to normal as plasma levels subsided. All other clinical measures (blood pressure, heart rate, level of consciousness and reflex activity) were unrelated to plasma drug levels. Cardiac comphcations were noted in a report on 68 cases of overdose (3 ) of which 57 patients had ECG abnormalities and 5 died within 24 hours of drug ingestion. The frequency of cardiac complications was almost double (46%) in patients who took over 2000 mg compared to those who took less (only 25%). 

A series of 8 patients is reported who developed cardiac complications following medication with a variety of psychotropic drugs, mainly phenothiazines and tricyclic antidepressants. Most of the patients showed arrhythmias, disorders of conduction, or both. Five of the patients, all of whom were receiving thioridazine, developed ventricular tachycardia or fibrillation. Many of the patients described showed no evidence of preexisting heart disease and 3 were below the age of 35, when the complications developed. In one female patient of 35 years ventricular tachycardia was fatal. 

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