Antidepressants specific classes

Table 7-18 summarizes the various factors to consider when choosing a specific class of antidepressant. 

The use of antidepressants outside the treatment of MDD tends to require specific agents. For example, the TCAs and SNRIs appear to be useful in the treatment of pain conditions, but other antidepressant classes appear to be far less effective. SSRIs and the highly serotonergic TCA, clomipramine, are effective in the treatment of OCD, but noradrenergic antidepressants have not proved to be as helpful for this condition. Bupropion and nortriptyline have usefulness in the treatment of smoking cessation, but SSRIs have not been proven useful. Thus, outside the treatment of depression, the choice of antidepressant is primarily dependent on the known benefit of a particular antidepressant or class for a particular indication. 

Uncomplicated, physically healthy outpatient without any contraindication to a specific class of antidepressants... 

Both nonexperimental and experimental studies reveal that while DTCA increases the size of the overall sales of a particular therapeutic class, brand-specific DTCA does not appear to have a statistically significant impact on the share of any particular brand within the therapeutic class. By increasing the size of therapeutic class sales but not affecting shares within the class, DTCA has ambiguous effects on consumer welfare. In particular, there is some experimental evidence suggesting that in the case of antidepressants. 

Tricyclic antidepressant medications were developed in the 1950s and 1960s. Because they affect multiple neurotransmitters in the brain, they are thought to have more side effects than the newer class of SSRIs, which target the specific neurotransmitter serotonin. 

For patients who do not respond to a specific antidepressant medication or who do not tolerate its side effects, other antidepressants of the same class or different classes (e.g., venlafaxine for a patient treated with a SSRI) can be tried. The few adult studies published thus far suggest that it is more efficacious to switch antidepressant classes than to stay within the same class, because of the probable heterogeneity in underlying depression mechanisms. Also, it has been suggested that severe depressions appear to respond better to antidepressants with both serotonergic and adrenergic properties (e.g., venlafaxine) (Poirier and Boyer, 1999). 

Many inhibitors of the amine transporters for norepinephrine, dopamine, and serotonin are used clinically. Although specificity is not absolute, some are highly selective for one of the transporters. Many antidepressants, particularly the older tricyclic antidepressants can inhibit norepinephrine and serotonin reuptake to different degrees. This may lead to orthostatic tachycardia as a side effect. Some antidepressants of this class, particularly imipramine, can induce orthostatic hypotension presumably by their clonidine-like effect or by blocking 04 receptors, but the mechanism remains unclear. 

Note the specific references to irritability, hostility, aggressiveness, impulsivity, akathisia (psychomotor restlessness), hypomania, and mania, a virtual prescription for violence. This new addition to the label, the implications of which having been largely overlooked, refers to children and adults. By indicating that nonpsychiatric patients can develop these reactions, the FDA class label challenges the commonly held belief that only patients with a bipolar history or vulnerability are at risk for developing antidepressant overstimulation. 

Within each class or subclass drugs are listed in order of frequency of prescription in the United Kingdom (1997 data). Abbreviations RIMA—reversible inhibitor of monoamine oxidase NaRI—noradrenaline reuptake inhibitor SNRI—serotonin and noradrenaline reuptake inhibitor NaSSA—noradrenaline and specific serotonergic antidepressant. 

Specific serotonin reuptake inhibitors, as the class name implies, act predominantly by preventing serotonin reuptake and have more limited effects on noradrenaline reuptake. Tricyclic antidepressants in general inhibit noradrenaline reuptake, but effects on serotonin reuptake vary widely desipra-mine and protriptyline have minimal potential for raising serotonin concentrations, whereas clomipramine possesses a greater propensity for blocking serotonin reuptake than for noradrenaline. The... 

The time for antidepressant onset of effect in BN is unclear. In the absence of data, the definition of a therapeutic trial from the depression hterature (4 to 8 weeks at a therapeutic dose) should be used. Since the majority of subjects will not experience a complete remission, and there are few data on predictors of response or whether switching to another class will improve response, a clear and specific target should be stated initially. Eor example, will the medication be continued if the patient has a 50% reduction in binge-purge episodes, or if abstinence from such behavior is the ultimate therapeutic goal. Optimal duration of treatment after response is also poorly defined. Most clinicians will treat for 6 months to 1 year and then re-evaluate the need for ongoing treatment. The evidence is mixed as to whether any early benefit is sustained, hence the decision to continue treatment should be made based on both initial response and the maintenance of that benefit. If the symptoms return within a few months after the antidepressant is discontinued, then the treatment may need to be reinitiated. 

Then came the new class of antidepressants, and it seemed like a miracle. These new medications were significantly more specific in rebalancing only those aspects of brain chemistry whose imbalance was causing depression. 

---