The 5 side effects of antidepressants

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 drugs with a high degree of efficacy 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, including norepinephrine reuptake inhibitors (SNRIs) and serotonin and norepinephrine reuptake inhibitors (IRSN).

• Related article: "Types of antidepressants: characteristics and effects"

Side effects of antidepressants

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 closely related to serotonin. Newly developed dual SNRI inhibitors 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 drugs that we will talk about cause very varied side effects, we will focus on those that appear more frequently and on those that have a special relevance clinic.

1. Monoamine oxidase inhibitors (MAOI)

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 blockage caused by these drugs increases the availability of norepinephrine, serotonin, and dopamine, which is effective in treating depression.

Currently MAOIs are rarely used because can cause severe hypertensive crisis if they interact with foods with 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.

• You may be interested: "Types of psychotropic drugs: uses and side effects"

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. In addition, 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 taking tricyclic antidepressants for long periods of time is not recommended; Not only are they addictive and cause withdrawal symptoms when you quit, but they have also been found to reduce the number of norepinephrine and serotonin receptors in the long term.

3. Selective serotonin reuptake inhibitors (SSRIs)

The name of SSRIs is due to the fact that they only interact with serotonin receptors, so that its action is more specific and safe than that of MAOIs and tricyclics. In addition, although annoying and unavoidable side effects appear when starting consumption, they tend to be reduced to some 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.

• Related article: "Serotonin syndrome: causes, symptoms and treatment"

4. Selective norepinephrine reuptake inhibitors (SNRIs)

Reboxetine is a recently developed drug that is as effective as SSRIs in treating depression symptoms. Its action is related to the selective inhibition of norepinephrine reuptake, and frequently is administered in conjunction with an SSRI in order to enhance the therapeutic effect of both drugs.

The norepinephrine agonism associated with ISRNs is particularly effective in treating symptoms such as apathy, deficits in social interaction, and memory and memory problems concentration. 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 the of norepinephrine without interacting with other receptors, as in the case of tricyclics, so that the associated reactions are scarce. What's more its therapeutic effects are superior to those of other antidepressants.

Since they act in 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, a feeling of fatigue, nausea, dry mouth, excessive sweating, memory problems and difficulties ejaculating and reaching the orgasm.