Tricyclic antidepressants: uses and side effects

Although they are less widely used today than SSRIs and other more modern antidepressants, Tricyclics were for many decades the pharmacological treatment of choice for disorders depressive

In this article we will describe what are tricyclic antidepressants, what they are used for and what are their most common side effects.

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What are tricyclic antidepressants?

Tricyclics are psychotropic drugs used to treat depressive disorderss, although in many countries they have been replaced as drugs of choice by other more effective antidepressants. The effects of drugs useful for treating depression are often associated with the agonism of depression. serotonin and of the noradrenaline.

The name of these drugs comes from their chemical structure: they are made up of three rings of atoms. Years after the appearance of tricyclic antidepressants, tetracyclics also emerged, which are made up of four rings instead of three.

From the moment it appeared

imipramine, the first antidepressant of this class, a large number of tricyclics have been manufactured with some differential characteristics. Among the most common are clomipramine, amitriptyline, nortriptyline, desipramine, maprotiline, doxepin, amoxapine, protriptyline, and trimipramine.

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What is your mecanism of action?

Tricyclic antidepressants are agonists of monoamines, a type of neurotransmitter very relevant in the nervous system of human beings. These potentiating effects affect serotonin, norepinephrine and, less significantly, dopamine.

Its main therapeutic activity is due to the inhibition of the reuptake of these neurotransmitters, which increases the availability of monoamines in the synaptic space. However, also collaterally affect histamine and acetylcholine, on which they exert an antagonistic effect.

Due to the low specificity of its mechanism of action, it does not target only the most relevant neurotransmitters as it happens with others. antidepressants, tricyclics may be helpful in relieving symptoms of depression but they also cause very serious side effects and adverse reactions. significant.

History of these drugs

Tricyclics were discovered in the process of making antipsychotic drugs. Clomipramine, a neuroleptic with a tricyclic structure, was synthesized in 1950. Information about this drug soon after led to the creation of imipramine, the first tricyclic used specifically to treat depression.

In recent decades the popularity of tricyclics has declined in most parts of the world due to the discovery of more effective antidepressant drugs and safe, particularly selective serotonin reuptake inhibitors (SSRIs) and fourth-generation antidepressants, such as venlafaxine and reboxetine.

Its functions

Despite their name, tricyclic antidepressants are not only used in cases of depression, but that throughout their history have been applied to a large number of psychological disorders different.

1. Depressive disorders

The main indication for tricyclics is treating depressive disorders, both major depression and other milder variants, particularly depression dysthymia. At present they are prescribed mainly in melancholic depression and in cases that do not improve through the consumption of other antidepressants with fewer side effects.

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2. Anxiety disorders

Some tricyclics are occasionally used to treat different anxiety disorders: imipramine has been shown to be effective in generalized anxiety disorder and panic disorder, while what clomipramine is still used in obsessive-compulsive disorder (closely related to depression) and amitriptyline in post-traumatic stress.

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3. Chronic pain

Among the disorders related to chronic pain that have been treated by tricyclic, fibromyalgia and neuropathic pain stand out; Serotonin and norepinephrine agonism is believed to indirectly influences endogenous opioid production, which have analgesic effects. Amitriptyline appears to be especially helpful in this regard.

4. Insomnia

The sedative side effects of tricyclic antidepressants have led to them being used occasionally to treat insomnia symptoms. However, it is important to bear in mind that there are other more specific drugs for these problems, and above all that psychological therapy is the most advisable way to face the difficulties to to sleep.

5. Eating disorders

Again, the therapeutic effects of tricyclics in eating disorders are associated with one of its most common side effects: weight gain. In particular, clomipramine is sometimes prescribed as part of therapy for anorexia nervosa.

6. Nocturnal enuresis and night terrors

Imipramine is effective in treating two childhood sleep disorders: nocturnal enuresis and night terrors. These effects are related to decreased delta or slow wave sleep, during which these episodes appear.

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Side effects of tricyclic antidepressants

Although the side effects associated with the use of tricyclic antidepressants depend largely on their agonism or antagonism towards certain neurotransmitters, in this section we will focus on the collateral reactions most commonly associated with this class of psychotropic drugs in their set.

As we mentioned in the previous section, between the most common side effects of tricyclic antidepressants we found sedation and weight gain; both are due to inhibition of histamine activity.

Acetylcholine receptor blockage causes side effects such as constipation, urinary retention, dry mouth, blurred vision and memory problems. On the other hand, the inhibition of alpha-adrenergic receptors is related to alterations in blood circulation, especially dizziness and orthostatic hypotension.

Among the serious adverse reactions to the consumption of tricyclics highlights neuroleptic malignant syndrome, consisting of the appearance of respiratory, cardiac and muscular alterations that can cause coma and, in approximately one fifth of cases, death. This syndrome appears to be more common in people over 50 years of age.

It should also be noted the high addictive potential of tricyclics, since drug tolerance develops easily. The appearance of a severe withdrawal syndrome after abrupt cessation of consumption is also a consequence of tolerance. In addition, the risk of overdose and suicide is remarkably high.