Drug information quarterly |
Principal Pharmacist, Maudsley Hospital, Denmark Hill, London SE5 8AZ.
Chief Pharmacist, Maudsley Hospital, Denmark Hill, London, E-mail: Eromona.Whiskey{at}slam.nhs.uk
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To review the evidence for this use of pramipexole in the treatment of unipolar and bipolar depression, a literature search on Embase and Medline was conducted in December 2003. The search was updated in July 2004. The reference sections of retrieved papers were searched for further relevant references.
RESULTS
There are limited data on the clinical use of pramipexole in affective disorders. Only two double-blind trials in bipolar depression and one in unipolar depression were retrieved. Most information is in the form of case reports and open studies. No dose-response relationships have been established and a wide range of doses has been employed in the reports.
CLINICAL IMPLICATIONS
In view of the fact that the evidence for the use of pramipexole is still limited at the time of writing, its routine clinical use cannot be recommended. The data appear promising, but further research is required to determine its role in affective disorders.
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More recently, an increased interest in the role of dopamine in the aetiology of depression has developed. This interest derives in part from the dopamine hypothesis of reward. In simple terms, pleasurable activity is associated with release of dopamine in the brain reward system (BRS). Conversely, inactivation of dopamine function can lead to anhedonia, the inability to experience pleasure, which is a core feature of depression. Furthermore, psychostimulants such as amphetamine and cocaine in low doses enhance dopamine release and cause activation and euphoria in normal volunteers. In higher doses or when taken repeatedly, they cause grandiosity, dysphoria and delusions. The withdrawal of these drugs frequently results in depression and anhedonia.
Data from animal studies and from limited human data indicate that dopamine agonists have antidepressant properties. The forced swimming test is one of the methods used to screen for antidepressant activity. When rats are forced to swim in a closed space from which they cannot escape, they will eventually stop attempting to escape and become immobile. Time to immobility in the swim test may be prolonged not only by antidepressants, but also by dopamine agonists. Furthermore, the anti-immobility effect of antidepressants in the forced swim test may be enhanced by co-administration of dopamine agonists (Maj & Rogoz, 1999; Renard et al, 2001). In humans, the dopamine agonist bromocriptine has been shown to be as effective as imipramine in the treatment of depression (Willner, 1983). For a review of dopamine in depression, see Willner (1995) and Rampello et al (2000).
Only a limited number of antidepressant drugs have potent activity on dopaminergic transmission. Of the antidepressants currently in use in the UK, the tricycle antidepressants only have a very weak effect on dopamine reuptake, while venlafaxine and sertraline have more substantial, but still limited, dopaminergic effects, albeit at higher doses. Bupropion, amineptine and nomifensine are dopaminergic antidepressants that act partly via inhibition of dopamine reuptake. Bupropion is licensed in the UK only for smoking cessation. Amineptine has been withdrawn from major markets because of its propensity for addiction, while nomifensine, a selective dopamine reuptake inhibitor, was withdrawn due to the risk of acute haemolytic anaemia and intravascular hemolysis. There is no dopamine agonist currently licensed for the treatment of depression.
Pramipexole is a recently introduced dopamine D2/D3 agonist with preferential binding affinity to D3 receptors. It was licensed in the UK in 1998 at doses ranging from 0.375 to 4.5 mg per day for idiopathic Parkinsons disease.
We conducted a literature search in December 2003 on Medline (1966-2003) and Embase (1980-2003) using the terms pramipexole, dopamine agonists, bipolar disorder and depression. The search was updated in July 2004. The reference section of retrieved papers were hand-searched for further relevant references.
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View this table: [in a new window] | Table 1. Papers retrieved in the literature search |
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Rektorová et al (2003) compared pramipexole with pergolide, another dopamine agonist for the treatment of depression in patients with Parkinsons disease. Only pramipexole showed a significant effect on the objective measures of depression, using the Montgomery-Asberg Depression Rating Scale (MADRS), whereas both drugs significantly alleviated depressive symptoms using self-rating.
A significant proportion of the case reports and open studies involved patients with refractory depression, in which pramipexole was used as an adjunct to ongoing antidepressants and mood stabilisers. Response in this group was in the range of 40-50%. This indicates that there may be a role for pramipexole as an adjunctive treatment in refractory depression. It is also noteworthy that some reports document either tolerance developing to the antidepressant effects (Ostow, 2002) or having only transient effects (Perugi et al, 2001).
Although there is information on the potential use of pramipexole in both unipolar and bipolar depression, it is not known whether it is especially effective in any particular subtype. An earlier report with another dopamine agonist, bromocriptine, however, suggests that the antidepressant response may be greater in bipolar patients (Silverstone, 1984). This information may be useful in assessing the risk-benefit ratio in individual patients.
The optimal dose of pramipexole in depression is not yet established. Doses have varied from as low as 0.125 mg/day to as high as 9 mg/day. No clear dose-response relationship is established. In the study conducted by Corrigan et al (2000), patients on 5 mg/day had greater improvements compared with 1 mg/day, but this was limited by poor tolerability (mainly nausea) at the higher dose. Gradual dose escalation is thus required.
The adverse effects observed with pramipexole in these reports have been largely consistent with that of dopamine agonism. Common side-effects include nausea, sleep disturbance, agitation, postural hypotension, headaches and tremor. It has also been uncommonly associated with excessive daytime somnolence and sudden sleep onset episodes. As most data relating to adverse effects come from patients with Parkinsons disease, it is not clear if the rates at which CNS adverse effects (such as hallucinations, dyskinesia, insomnia, sleep attacks) occur will be any different than in patients with depressive illness. At least four cases of hypomania have been reported with pramipexole (Sporr et al, 2000; Perugi et al, 2001; Goldberg et al, 2004; Zarate et al, 2004).
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M., et al
(2003) Pramipexole and pergolide in the treatment of depression
in Parkinsons disease: a national multicentre prospective randomised
study. European Journal of Neurology,
10, 399
-406.[CrossRef][Medline]
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