Antidepressant drugs classification

We do not currently have a complete and adequate explanation of how antidepressant drugs work. What we do know is that all effective antidepressants have identifiable immediate interactions with one or more monoamine neurotransmitter receptor or enzyme. These immediate actions provide the pharmacological foundation for the current classification of the different antidepressants. 

Original drug classifications in the 1960s emphasized that there were important distinctions between the antidepressants (e.g., tricyclic antidepressants) versus the anxiolytics (e.g., benzodiazepines) available at that time. This reflected the diagnostic notions then prevalent, which tended to dichotomize major depressive disorder and... 

Scientists were looking for drugs to treat different medical problems when their observations almost accidentally led them to the study of depression and its treatment. Many scientists continued in this new direction to the discovery of the current three classifications of antidepressant drugs used today monamine oxidase... 

Fig. 19.1 Flow chart of the evolution of antidepressant drugs and classification by mechanism of action.

Amphetamine [XXII) is a central stimulant and many would not classify it with the antidepressant drugs proper. It has, however, been extensively used in the treatment of depression, it produces euphoria and some at least of its actions may be due to inhibition of monoamine oxidase. However, it also inhibits dopamine- S-oxidase, impairs the noradrenaline binding capacity of the brain and has direct sympathomimetic activity. Its classification with the antidepressants seems, therefore, to be justified, but it is not included with the monoamine oxidase inhibitors, since only a small part of its action can be attributed to enzyme inhibition. Amphetamine is a potentially addictive drug and it should be used cautiously and over short periods of time. Other compounds which are used, if at all, only for the treatment of mild depression, include methylphenidate [XXIII), pipradol [Table 5.2) and deanol (XXIV). The last named compound is interesting since it may owe its effectiveness to a stimulant action on acetylcholine synthesis > . ... 

A. Classification and Pharmacokinetics The major classes of antidepressant drugs are shown in Figure 30-1 tricyclic antidepressants, heterocyclic antidepressants, selective serotonin reuptake inhibitors, and monoamine oxidase inhibitors. 

The antidepressants available in the United States are classified by either their chemical structure (e.g., the tricyclics, TCAs) or their actions on neurotransmitters (e.g., SSRIs and MAOIs) or simply as other (e.g., Wellbutrin). In the future, the classification of the antidepressants may become more confusing as new drugs are developed that are neither TCAs, SSRIs, or MAOIs. 

Krijzer FNCM, van der Molen R (1987) Classification of psychotropic drugs by rat EEG analysis the anxiolytic profile in comparison to the antidepressant and neuroleptic profile. Neuropsychobiology 18 51-56 Krijzer F, Koopman P, Olivier B (1993) Classification of psychotropic drugs based on pharmaco-electrocorticographic studies in vigilance-controlled rats. Neuropsychobiology 28 122-137... 

MAO inhibitors are another group of antidepressant medications that have historically been used to treat major depressive disorders. Currently, this classification of medications is considered a second-line or third-line treatment of depression (Brophy, 1991 Tierney et al., 1997). There are times however, that this group of drugs can be utilized as the first line of treatment for depression of an atypical nature (Tierney et al., 1997). Generally, these medications with their dangerous treatment-effect profiles should only be considered after the tricyclic or the newer classifications of antidepressants have been tried (Tierney et al., 1997). 

According to the 1964 WHO classification there are 7 groups 1. alkaloids (LSD, mescalin, opium, etc.), 2. barbiturates and other sleeping drugs, 3. alcohol, 4. cocaine, 5. hashish and marihuana, 6. halludl-logens, 7. stimulants or antidepressants (e.g. amphetamines). 

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