What’s the deal with tricyclic antidepressants?
This class of antidepressants is generally used for treatment of depression, often in conjunction with psychotherapy. May also be used in chronic pain syndromes.
The tricyclic antidepressants work by blocking serotonin and norepinephrine reuptake by adrenergic nerves. The result of this is an increase in serotonin and norepinephrine at the nerve synapse; this is thought to elevate mood and reduce depression.
The role of norepinephrine in the heart is pertinent because of the relationship between tricylic medications and adrenergic nerve receptors. Adrenergic receptors receive adrenalin and noradrenalin; or epinephrine and norepinephrine, this is compared to the cholinergic receptors that receive acetylcholine (catecholamines).
amitriptyline / Elavil
doxepin / Sinequan
imipramine / Norfranil, Tipramine
nortriptyline / Pamelor, Aventyl
CNS: anxiety, ataxia, coma, chills, delusions, disorientation, fatigue, fever, headaches, insomnia, peripheral neuropathy, tremor
CV: Arrhythmias; including tachycardia, prolonged AV conduction, heart block. Hypertension, Myocardial Infarction (MI), ECG changes, orthostatic hypotension, palpitations
Significant cardiac involvement is due to the adrenergic receptors in the myocardium of the heart. Under normal circumstances the adrenergic receptors (beta) receive norepinephrine and function in increasing heart rate and decreasing contractility. Where: CO (cardiac output) + PR (peripheral resistance) = BP (blood pressure). When there is an increase in norepinephrine as a result of the tricyclic medications allowing increased concentrations at the synapse, you will have an increase in heart rate (tachycardia) as well, a likely decrease in blood pressure related to the lowered PR created from the decreased contractility and CO. Patients with a cardiac history may be evaluated as to whether or not they would be safe on this medication.
ENDO: changes in blood glucose, inappropriate anti-diuretic hormone (ADH). Gynecomastia. *the ADH will increase sodium reabsorption in the distal convoluted tubule of the nephron in the kidney; significant due to the effect that increased fluid volume has on CO.
HEME: Bone marrow depletion, eosinophilia, leukopenia, thrombocytopenia
Patients who are in an acute recovery phase following an MI should refrain from using tricyclic antidepressants. MAO inhibitors should not be used within 14 days of tricyclic antidepressants due to the risk of seizures and death.
Due to the risk of changes in blood glucose levels, patients with diabetes should be carefully evaluated as to the safety of this medication.