Attenuation of response to serotonin reuptake inhibitors

Tardive dysphoria: antidepressant-induced chronic depression

Objectives: A significant number of depressed individuals experience inadequate benefit from long-term antidepressant use. This paper investigates the hypothesis that in some individuals persistent use of antidepressants may be prodepressant.

Methods: Literature regarding the effect of long-term use of antidepressants was reviewed by searching PubMed and Ovid data bases with terms: antidepressant tachyphylaxis, treatment-resistant depression, chronic depression and antidepressant tolerance.

Results: Antidepressant treatment-resistant patients frequently had a positive initial response to antidepressants. When resistance appeared, initial increases in dose or medication changes usually resulted in transient improvement. Eventually, the episodic course of the original depressive illness was replaced with a continuous, unresponsive depressive syndrome. We propose the term tardive dysphoria to describe this phenomenon.

Conclusions: The phenomenon of antidepressantinduced depression, or tardive dysphoria, needs to be experimentally examined in blinded, randomised antidepressant discontinuation studies.

Do antidepressants have any potential to cause addiction?

Addiction/dependence is a syndrome in which the hallmark is a compulsive pattern of drug use. Most authorities do not regard antidepressants as causing addiction but this has been challenged. This debate is explored drawing on case reports and related clinical and pharmacological data. An extensive literature review identified 21 English language case reports of antidepressant addiction (DSM-IV 'substance dependence' criteria) published since 1963. Sixteen involved tranylcypromine or amineptine and may reflect their dopaminergic and stimulant properties. Subject characteristics included male sex (14/21), personality problems (10/21) and prior substance misuse (14/21). Withdrawal or discontinuation symptoms have long been recognized with antidepressants but other features of addiction such as tolerance and compulsive use are exceptionally rare. Common clinical problems are patients taking subtherapeutic dosages and prematurely stopping antidepressants. The pharmacodynamic profiles of most antidepressants and the absence of acute 'desirable' effects make addiction theoretically unlikely. It is concluded that, with the exception of tranylcypromine and amineptine, antidepressants do not have a clinically significant liability to cause addiction. Tranylcypromine and amineptine should be avoided in those with a history of substance misuse. Patients prescribed other antidepressants should be told that they are not addictive.

Selective serotonin reuptake inhibitors in affective disorders--II. Efficacy and quality of life

Since their introduction, the selective serotonin reuptake inhibitors (SSRIs) have become one of the most widely used classes of medication in psychiatry. Their popularity is based on apparent efficacy over a wide range of disorders and a favorable side-effect profile. However, as with any psychotropic medication, considerable data are required to define where a drug works and where it does not. There is now a wealth of evidence demonstrating that SSRIs may differ in their efficacy profiles in certain depressive symptoms, in different subtypes of depression, with respect to their ability to maintain efficacy over time, on broader outcomes such as quality of life, and in the consistency of the usually effective minimum therapeutic dose across the age spectrum and across indications. Although this review includes data on all SSRIs, it focuses on fluoxetine and sertraline, which in addition to being the most widely used SSRIs are also the most widely studied. The relative quantity and quality of data on these two SSRIs means that it is possible to make relatively firm inferences regarding their differential effects on affective symptoms and quality of life.

SSRI-induced extrapyramidal side-effects and akathisia: implications for treatment

The selective serotonin reuptake inhibitors (SSRIs) may occasionally induce extrapyramidal side-effects (EPS) and/or akathisia. This may be a consequence of serotonergically-mediated inhibition of the dopaminergic system. Manifestations of these effects in patients may depend on predisposing factors such as the presence of psychomotor disturbance, a previous history of drug-induced akathisia and/or EPS, concurrent antidopaminergic and/or serotonergic therapy, recent monoamine oxidase inhibitor discontinuation, comorbid Parkinson's disease and possibly deficient cytochrome P450 (CYP) isoenzyme status. There is increasing awareness that there may be a distinct form of melancholic or endogenous depression with neurobiological underpinnings similar to those of disorders of the basal ganglia such as Parkinson's disease. Thus, it is not surprising that some individuals with depressive disorders appear to be susceptible to developing drug-induced EPS and/or akathisia. In addition, the propensity for the SSRIs to induce these effects in individual patients may vary within the drug class depending, for example, on their selectivity for serotonin relative to other monoamines, affinity for the 5-HT2C receptor, pharmacokinetic drug interaction potential with concomitantly administered neuroleptics and potential for accumulation due to a long half-life. The relative risk of EPS and akathisia associated with SSRIs have yet to be clearly established. The potential risks may be reduced by avoiding rapid and unnecessary dose titration. Furthermore, early recognition and appropriate management of EPS and/or akathisia is required to prevent the impact of these effects on patient compliance and subjective well-being. It is important that the rare occurrence of EPS in patients receiving SSRIs does not preclude their use in Parkinson's disease where their potentially significant role requires more systematic evaluation.