Since the discovery of the antidepressant effects of monoamine oxidase inhibitors (MAOIs) and the popularization of tricyclics, great progress has been made in this area of pharmacotherapy. Currently there are medications with a high degree of effectiveness and that cause few adverse reactions.
In this article we will analyze the side effects of the main types of antidepressants: MAOIs, tricyclics, serotonin reuptake inhibitors (SSRIs) and fourth-generation antidepressants, which include norepinephrine reuptake inhibitors (SNRIs) and serotonin and norepinephrine reuptake inhibitors (SNRIs).
All psychotropic drugs that are effective in treating depressive symptoms are monoamine agonists, a group of neurotransmitters Some enhance the action of norepinephrine, while others are more related to serotonin. The dual SNRI inhibitors, which have recently appeared, are associated with both neurotransmitters.
The side effects of antidepressants are due both to their monoaminergic action and to idiosyncratic mechanisms of some of them. Although the five classes of medications we will talk about cause very varied side effects, we will focus on those that appear most frequently and those that have special clinical relevance.
1. Monoamine oxidase inhibitors (MAOIs)
As their name suggests, MAOIs inhibit the activity of the enzyme monoamine oxidase, which breaks down monoamines to prevent them from becoming excessively concentrated in the synaptic space. The enzyme blockade caused by these drugs increases the availability of norepinephrine, serotonin and dopamine, which is effective in the treatment of depression.
Currently, MAOIs are little used because They can cause severe hypertensive crises if they interact with foods containing tyramine, like chocolate, coffee or banana; This phenomenon is known as the “cheese effect.” They also cause milder side effects: heart rhythm disturbances, insomnia, headaches, anorgasmia, weight gain, etc.
2. Tricyclic antidepressants
Tricyclic antidepressants, such as clomipramine and imipramine, inhibit the reuptake of serotonin, norepinephrine and, to a lesser extent, dopamine. Its side effects are important and are mainly due to the agonism of norepinephrine and the collateral antagonism of two other neurotransmitters: acetylcholine and histamine.
Among the adverse reactions to tricyclics highlights neuroleptic malignant syndrome which can cause coma and even death. Additionally, excessive sedation, memory problems, constipation, urinary retention, weight gain, hypotension and dizziness appear. There is a strong risk of dependence and excessive consumption can cause overdose.
Scientific research has shown that it is not advisable to take tricyclic antidepressants for prolonged periods of time; Not only are they addictive and cause withdrawal syndrome when they are abandoned, but it has been discovered that in the long term they also reduce the number of norepinephrine and serotonin receptors.
The name SSRIs is due to the fact that They only interact with serotonin receptors, so its action is more specific and safer than that of MAOIs and tricyclics. Furthermore, although annoying and inevitable side effects appear when starting consumption, they usually reduce to a certain extent and become more tolerable after one or two weeks of treatment.
Drugs such as fluoxetine, sertraline and citalopram cause anxiety, akathisia, tremors, diarrhea, vomiting and sexual disturbances, including decreased desire, difficulties with arousal and delayed orgasm. We speak of “serotonin syndrome” when these reactions are particularly intense
Reboxetine is a recently developed drug that is as effective as SSRIs in treating symptoms of depression. Its action is related to the selective inhibition of norepinephrine reuptake, and frequently is administered together with an SSRI in order to enhance the therapeutic effect of both medications.
The norepinephrine agonism with which SNRIs are associated is especially effective in treating symptoms such as apathy, deficits in social interaction, and memory and concentration problems. Its side effects are milder than those of SSRIs; The most common are insomnia, nausea, sweating, constipation and dry mouth.
5. Serotonin and norepinephrine reuptake inhibitors (SNRIs)
In recent years, some psychotropic drugs have appeared, such as venlafaxine, which combine the specific agonism of serotonin with that of norepinephrine without interacting with other receptors, as happens with tricyclics, so that the associated reactions are few. Besides Its therapeutic effects are superior to those of other antidepressants
Because they act on the same pathways, SNRIs cause side effects similar to those of the other drugs we have mentioned. Other symptoms may include drowsiness or insomnia, headaches, dizziness, feelings of fatigue, nausea, dry mouth, excessive sweating, memory problems, and difficulties ejaculating and reaching orgasm.
