Antidepressants are chemicals that are correct and depressed mood. These thymus-analeptics are stimulants psychic or psycho-analeptics that act on thymic functions. All antidepressants have an activity on monoamine neurotransmitters, but they do not interfere with the mono-amines in the same way.
An antidepressant is a medication primarily used to treat certain depression and certain anxiety disorders whose effects appear after two or three weeks. There are different classes of antidepressants with similar efficacy. However the effectiveness is demonstrated and affirmed by studies commissioned by laboratories producing these drugs.
Mechanisms of action
The mechanism of action of antidepressants is generally associated with an effect on neurotransmitters (particularly serotonin and norepinephrine).
* The SSRIs (selective serotonin reuptake) increased the concentration of serotonin in the synapse by preventing its reuptake in the presynaptic neuron (see synapse). This class of anti-depressants is recent. The famous Prozac is one.
* MAOIs (monoamine oxidase inhibitors) increase the concentration of serotonin by inhibiting the enzymes (monoamine oxidase or MAO) responsible for its degradation. Their use requires monitoring of the very restrictive diet and they are now rarely used.
* The tricyclic antidepressants inhibit the reuptake of various neurotransmitters, including serotonin, norepinephrine and dopamine. These antidepressants are the oldest and still very effective despite the sometimes troublesome side effects.
Classes of antidepressants
Depending on their structure and their mechanism of action, antidepressants are often classified into three groups. The first group of substances have a tricyclic structure (ATC), the second group and not always those of the third group did not. With few exceptions, the substance of the first and second group of variably inhibit reuptake of both noradrenaline (norepinephrine) and serotonin. The inhibitor reboxetine however reuptake of norepinephrine. The third group of substances are inhibitors selective serotonin reuptake inhibitors (SSRIs). For some drugs, the effect to be partially due to mechanisms other than inhibition of reuptake of these amines.
They can also be classified as follows:
* Monoamine oxidase inhibitors (MAOIs)
* Tricyclic antidepressants (ATC)
* Inhibitors selective serotonin reuptake inhibitors (SSRIs)
* Reuptake inhibitors of serotonin-norepinephrine (SNRIs)
* Inhibiting reuptake of norepinephrine (NARI)
* New antidepressants
* Tetracyclic antidepressants
There is evidence that St. John's wort (Hypericum perforatum) is effective as an antidepressant in patients with mild to moderate depression, but not severe depression. Questions remain, however, on its long-term safety and optimal dose. The mechanism of action has been suggested is inhibition of reuptake of serotonin.
In case of overdose, TCAs are more toxic than SSRIs.
TCAs and related substances, and SSRIs may be taken within 2 weeks after stopping the MAOI.
All conventional antidepressants would be equally effective. However, the latter is regularly questioned. So many negative studies (that is to say, does not prove the effectiveness of these medications) are not published, which distort their evaluation.
Among antidepressants called "second generation", mirtazapine, escitalopram, venlafaxine and sertraline might be a bit more effective, better tolerated as escitalopram and sertraline.
Antidepressant treatments showed only small improvements compared to placebo, the difference in efficacy between antidepressants and placebo increased with the severity of depression, but this difference remains small, even for severe depression. The decision to treat a depressed patient in the first line does not mean that antidepressants should be prescribed routinely. A support non drug (psychotherapy) is certainly preferable in minor depression.
Their efficiency is reached only in 2-3-4 weeks of treatment, this physiological phenomenon is known as the downregulation.
Several figures of French psychiatry emphasized the collusion between the pharmaceutical industry and prescribers in the treatment of depression.
The side effects of antidepressants vary among individuals. These variations are more important to one individual to another as one molecule to another.
Antidepressants can have side effects and is the leading cause of discontinuation of the patient(?).In addition, it happens that some patients do not respond to antidepressants.
Sexual dysfunction (anorgasmia, decreased libido, etc..) Are among the side effects most often reported. This issue must be taken into account when an indication to the extent that improves one side, the mood of the patient, may be offset by something that empire sex life with its impact on life torque. As with any medical indication, balance "the expected benefits and disadvantages" should be seriously considered and discussed with the patient. Sexual dysfunction may be the result of the use of an SSRI. This dysfunction may be permanent(?). (in English: Post SSRI Sexual Dysfunction (PSSD)).
Akathisia is a side effect of antidepressants, it is classified as undesirable effect deadliest antidepressants(?). It may indeed cause murderous impulses and / or suicidal.
Serotonin syndrome is a potentially fatal complication linked to antidepressants reuptake inhibitors selective serotonin, MAOIs, tricyclic ... According to some authors, the cases of serotonin syndrome are widely underestimated.
Side effects with the first and second groups
* First group: orthostatic hypotension and impaired cardiac conduction (quinidine-like effect), especially among the elderly in case of cardio-vascular and existing high doses. In case of overdose, arrhythmias to potentially fatal outcome can occur.
* Prime Group and certain substances of the second group: anticholinergic effects (dry mouth, urination disorders, disorders of accommodation ...). This can cause problems in patients with prostatic hypertrophy or narrow angle glaucoma, or if concomitant therapy with other drugs acting anticholinergic.
* With amitriptyline, doxepin, maprotiline, mianserin, mirtazapine and trazodone sedation. This property is useful sedative in cases of anxiety associated with depression, the main outlet or single day will be preferably in the evening. Other antidepressants have little or no sedative or even slightly challenging (desipramine, nortriptyline) and are sometimes responsible for anxiety, agitation and insomnia.
* With Trazodone: risk of priapism.
* Especially with mianserin (may be also related with mirtazapine): risk of agranulocytosis.
Side effects with SSRIs
* Gastrointestinal common (nausea, diarrhea ...).
* Central frequent side effects (headache, dizziness, agitation, insomnia ...).
* Serotonin syndrome in patients treated with high doses of SSRIs, especially in combination with other serotonergic drugs. This syndrome is characterized inter alia by hyperthermia, agitation, myoclonus, and rarely, seizures, ventricular arrhythmia, sometimes with fatal outcome.
* Events extrapyramidal.
* Bleeding, P. ex. at the gastro-intestinal, skin and mucous membranes.
* Hyponatremia especially among the elderly.
Read also Schizophrenia