Antidepressants are a class of drugs for the treatment of depression and melancholy, pessimistic, negative feelings, which can provide emotional boost, improve mood, enhance ability to think and make energy better. There are many kinds of such drugs, since it was launched in the market in 1950’s, which have made rapid development, especially in last decade, there have been many new antidepressants. Such drugs have effect not only on depression but also on anxiety, forcing state and phobia.
According to the different chemical structure, antidepressants can be divided into three categories: monoamine oxidase inhibitors, tricyclic antidepressant agents and heterocyclic antidepressants.
Monoamine oxidase inhibitors: It is the first anti-depressant discovered in the early 50s, and it was widely used as it had a certain effect. But it was quickly replaced by tricyclic antidepressants because of the serious side effects. In recent years, researchers have found that tricyclic antidepressants also have some shortcomings, and they have poor efficacy on some treatment-resistant depression, so researchers began to reevaluate and develop the monoamine oxidase inhibitors.
Monoamine oxidase inhibitors mainly are hydrazine and non-hydrazine. Phenelzine is the mainly administrated in current clinical therapy as hydrazine, which has good efficacy and less side effects, and phenylpropylamine is an effective non-hydrazine drug.
Monoamine oxidase inhibitors are mainly used for the treatment of non-endogenous depression, with the symptoms of atypical depression such as fear, hypochondria, and obsessive-compulsive symptoms. The depression can be improved with the administration of such drugs, on which the application of tricyclic antidepressants doesn’t work well. Therefore, these drugs can improve the patient mood, increase their interest in things, reduce anxiety, nervous, and increase the activities. But such drugs have no significant effect on a variety of uncomfortable physical symptoms.
The main adverse reactions are: insomnia, dizziness, headache, orthostatic hypotension, tendon hyperreflexia, tremor, weakness, sweating, dry mouth, and some patients have such symptoms as drowsiness, difficulty urinating, impotence and so on. Skin allergic reactions may also occur. Serious side effects are: hypertensive crisis and poisoning-induced liver injury, so blood pressure and liver function should be measured regularly before and after medication. Patients with history of liver disease and cerebrovascular disease are prohibited to use it, and the elderly should use it with caution.
Tricyclic antidepressants: they are the most widely used antidepressant drug of first choice. There are many different types of tricyclic antidepressants, and the main drugs used are: imipramine, clomipramine, amitriptyline and so on. These drugs not only make the feeling excited, but also have the sedative effect; therefore, they also have therapeutic effect on insomnia symptoms. Its side effects include: dry mouth, constipation, blurred vision, difficulty urinating, urinary retention, tremors or seizures may occur in few cases and so on.
Tricyclic antidepressants can be used for a variety of depression, but also have a certain effect on the panic attack, the forcing state, bulimia, attention deficit hyperactivity disorder (ADHD) and enuresis. Contraindications are: severe cardiovascular and cerebrovascular disease, glaucoma, epilepsy, prostatic hypertrophy, urinary retention, intestinal paralysis and woman in early pregnancy or plan to have a baby should also be prohibited to use it.
Heterocyclic antidepressants: tricyclic antidepressants also have many disadvantages: the treatment efficiency is only 60% ~ 80% and work slowly as it usually works in about 2 weeks, so, for critically ill patients, the adverse reactions due to this drug often happen before it works, which resulted in that patients won’t be adhere to taking it within 1 or 2 weeks, and even someone will suicide in this period; tricyclic antidepressants have very apparent side effects as well. In view of the above shortcomings, from the 1960’s, researchers started to develop a new generation of antidepressant drugs.
Heterocyclic antidepressants include the following as:
① tetracyclic antidepressant drugs: with the representative as Maprotiline (Ludiomil), not only have an antidepressant effect, but also have strong sedative effects, and its efficacy is similar to tricyclic antidepressants, while its side effects are light The main side effects are dry mouth, dizziness, blurred vision, drowsiness, constipation, weight gain. Rash is common, less cardiac toxicity, as well as occasional seizures. Therefore, it is prohibited to be used for the treatment of patients with the history of epilepsy and skin allergies. As the side-effects are light, it can be used for the elderly and infirm.
② drugs not inhibit the uptake of amine: with the representative as the mianserin (Mianserin Tolvon), This drug has effects on depression such as sedative, anxiolytic and antidepressant, and are effective to treat anxiety, suicidal ideas, somatization symptoms and insomnia. The advantages of this drug are that side-effects are light, safe,, suitable for the elderly patients. Treatment is convenient with a smaller dose and it is welcome with simple medication as taking one or half tablet every night. The main side effects: may induce seizures or leukopenia. Which is rare, but it should be paid close attention as regularly measure blood investigations, especially when it applied for the elderly, should inspect whether the symptoms of infection occur.
(3) serotonin reuptake inhibitors: belongs to 5-HT medicine, in recent years, such kind of drugs has made rapid development, and there are more than 30 kinds, among which five kinds are common use including fluoxetine (fluoxetine, Prozac ), paroxetine, fluvoxamine, sertraline and gly-fluoroaniline.
With fluoxetine, for example, the drug not only has anti-depressant, boost mood effects but also is effective on the treatment of obsessive-compulsive disorder. The administration is simple, just to take one pill after breakfast everyday. Its main side effects will occur within 1 week after medication, then patients will gradually adapt to it. Symptoms of side effects are as follows: gastrointestinal reactions, such as nausea, vomiting, anorexia and diarrhea. Other side effects are excitement, anxiety, dry mouth, sweating, headache, daytime sleepiness, night insomnia, constipation, and sexual function disorders. The drugs reduce the weight and lower blood glucose. Patients with liver and kidney dysfunction and the elderly should used it with caution, children, pregnant women, lactating women and patients with a history of epilepsy and drug allergy should be banned to use it.
Such drugs and tricyclic drugs can’t be used with the monoamine oxidase inhibitor togheter, and if the medication is necessary, the administration of these drugs should be discontinued for at least 2 weeks or more, and fluoxetine needs to be suspended for 5 weeks to 7 weeks.
In addition to these three types of anti-depressants mentioned above, some antipsychotics also have antidepressant, anxiolytic effect, and they are commonly used as supplement therapy for depression and anxiety disorders, especially for post-schizophrenic depression. Application of these drugs has dual role of treating depressant and psychiatric symptoms. Commonly used drugs are sulpiride, chlorprothixene and thioridazine.
Mechanism of antidepressant drugs
The material basis of depression is related with neurotransmitters in the brain. Neurotransmitters are chemical substances to transmit information from one nerve cell to another nerve cell as the nerve cells don’t contact with each other. There is a small gap between them called synapses. When a nerve impulse transmitted, nerve cell which set out information will release a small number of neurotransmitters, which transmit the signal into the next nerve cell, and in such way it spreads throughout the body. Once a nerve pass over a synapses, a number of specific enzymes will clear the neurotransmitter so that the next nerve impulses can be delivered.
Depression is closely related with the low level of a number of specific neurotransmitters, such as 5-HT. Some anti-depressants increase the levels of these neurotransmitters by interfering with enzymes that remove the neurotransmitters, which is known as reuptake inhibitors (reuptake inhibition). Different antidepressants have different roles on various neurotransmitters. A variety of antidepressant drugs may have effect on the same neurotransmitter, but each has its own slightly unique role, which makes them distinguished from each other.
The choice of antidepressants depends on your symptoms. So, you have to tell doctor all your symptoms, so that you will get drug therapy which is most suited to your condition.