Stimulants in bipolar disorder: beyond common beliefs

Superior chronic tolerability of adjunctive modafinil compared to pramipexole in treatment-resistant bipolar disorder

BACKGROUND

Suboptimal outcomes are common in bipolar disorder (BD) pharmacotherapy, and may be mitigated with novel adjunctive agents such as modafinil (a low-affinity dopamine transport inhibitor) and pramipexole (a dopamine D2/D3 receptor agonist). While uncontrolled long-term effectiveness data have been reported for these treatments, reports specifically assessing their comparative acute versus chronic tolerability in BD are lacking. Such information, particularly in relation to discontinuation causes, has substantial relevance, providing initial indications to clinicians which treatment may be better tolerated, and to researchers which agent ought to be assessed in longer-term controlled trials.

METHODS

BD outpatients assessed with the Systematic Treatment Enhancement Program for Bipolar Disorder (STEP-BD) Affective Disorders Evaluation, and followed with the STEP-BD Clinical Monitoring Form, were naturalistically prescribed adjunctive modafinil or pramipexole, and somatic/psychiatric intolerability discontinuation rates were compared.

RESULTS

Among 63 BD outpatients (mean ± SD age 43.5 ± 14.3 years, 60.3% female, 42.9% type I, 44.4% type II, 12.7% type not otherwise specified), taking 3.5 ± 1.5 (median 3) concurrent prescription psychotropics, adjunctive modafinil (n=24) for 626.9 ± 863.9 (286) days versus pramipexole (n=39) for 473.7 ± 613.4 (214; p=0.51) days yielded a 26.0% lower somatic/psychiatric intolerability discontinuation rate (12.5% vs. 38.5%; p<0.05), with most of the difference accounted for by more pramipexole somatic intolerability discontinuations, due to nausea and sedation, after the first 12 weeks of treatment.

LIMITATIONS

No placebo comparison group. Small sample of predominantly female Caucasian insured outpatients, taking complex concurrent medication regimens.

CONCLUSIONS

Further studies are warranted to assess our preliminary observation that modafinil, compared to pramipexole, may be better tolerated for longer-term BD treatment.

Use of adjunctive stimulants in adult bipolar depression

Bipolar depression represents a high priority research field, due to its pervasiveness, and high economic and personal (suicidality, impaired function, quality of life) costs, and the limited evidence base to inform therapeutics. Mood stabilizers and second-generation antipsychotics for bipolar depression are commonly only partially effective, and their side-effects may overlap with depressive symptoms such as hypersomnia, daytime drowsiness, fatigue, psychomotor retardation, and weight gain. Moreover, the use of antidepressants in bipolar depression is controversial due to concerns regarding the risks of inefficacy or switching to mood elevation. Stimulants and related compounds such as modafinil and armodafinil have on occasion been used as adjuncts in bipolar depressed patients with encouraging results, but their use is limited by the paucity of systematic evidence of efficacy and safety. The present review aims to provide an updated perspective on the use of stimulants and stimulant-like medications in adult bipolar depression, considering not only recent randomized controlled trials, but also open naturalistic studies, in order to clarify the strengths and limitations of using these agents.

The vigilance regulation model of affective disorders and ADHD

According to the recently proposed vigilance model of affective disorders (vigilance in the sense of "brain arousal"), manic behaviour is partly interpreted as an autoregulatory attempt to stabilise vigilance by creating a stimulating environment, and the sensation avoidance and withdrawal in Major Depressive Disorder (MDD) is seen as an autoregulatory reaction to tonically increased vigilance. Indeed, using a newly developed EEG-based algorithm, hyperstable vigilance was found in MDD, and the contrary, with rapid drops to sleep stages, in mania. Furthermore, destabilising vigilance (e.g. by sleep deprivation) triggers (hypo)mania and improves depression, whereas stabilising vigilance, e.g. by prolonged sleep, improves mania. ADHD and mania have common symptoms, and the unstable vigilance might be a common pathophysiology. There is even evidence that psychostimulants might ameliorate both ADHD and mania. Hyperactivity of the noradrenergic system could explain both the high vigilance level in MDD and, as recently argued, anhedonia and behavioural inhibition. Interestingly, antidepressants and electroconvulsions decrease the firing rate of neurons in the noradrenergic locus coeruleus, whereas many antimanic drugs have opposite effects.

Varenicline as a smoking cessation aid in schizophrenia: effects on smoking behavior and reward sensitivity

RATIONALE

Smoking rates are up to five times higher in people with schizophrenia than in the general population, placing these individuals at high risk for smoking-related health problems. Varenicline, an α4β2 nicotinic acetylcholine receptor partial agonist, is a promising aid for smoking cessation in this population. To maximize treatment efficacy while minimizing risks, it is critical to identify reliable predictors of positive response to varenicline in smokers with schizophrenia.

OBJECTIVES

Negative symptoms of schizophrenia are related to dysfunctions in the brain reward system, are associated with nicotine dependence, and may be improved by nicotine or nicotinic receptor agonists, suggesting that smoking cessation may be especially difficult for patients with substantial negative symptoms. The purpose of the study was to evaluate negative symptoms as predictors of response to varenicline.

METHODS

Patients with schizophrenia (N = 53) completed a 12-week smoking cessation trial combining varenicline with cognitive behavioral therapy. Negative symptoms were assessed via the Scale for the Assessment of Negative Symptoms (Andreasen 1983). Outcomes included smoking abstinence as assessed by self-report and expired carbon monoxide. Change in performance on a probabilistic reward task was used as an index of change in reward sensitivity during treatment.

RESULTS

At week 12, 32 participants met criteria for 14-day point-prevalence abstinence. Patients with lower baseline symptoms of affective flattening (more typical affect) were more likely to achieve smoking abstinence and demonstrated larger increases in reward sensitivity during treatment.

CONCLUSIONS

These data suggest that affective flattening symptoms in smokers with schizophrenia may predict response to varenicline.