Research reportIndications for antidepressant drug prescribing in general practice in the Netherlands
Introduction
Antidepressant drug use has increased dramatically over the past decade (Rosholm et al., 1997, Lawrenson et al., 2000). Possible explanations for this increase are thought to be many, including the introduction of new antidepressants, increased depression awareness, acceptability of pharmacological treatment, better diagnosis, broadened indications and longer treatment periods (Barbui et al., 1999, Stafford et al., 2001, Pirraglia et al., 2003, Hemels et al., 2002, Meijer et al., 2004). The intensity and dynamics of the use of antidepressants in large populations can nowadays quite easily be estimated using databases encompassing prescription data (Tamblyn et al., 1995, Melfi and Croghan, 1999, Henriksson et al., 2003). There are, however, shortcomings when using these databases as they often only contain prescription data and no clinical data including information on the type of illness the treatment is intended for.
In the Netherlands antidepressants are approved not only for use in patients who suffer from depression but also for patients with nocturnal enuresis, social phobia, generalized anxiety disorders, obsessive–compulsive disorders, panic disorders and eating disorders (Anon, 2000). In addition, the antidepressants are used for some clinically accepted off-label indications such as sleeping disorders (Walsh, 2004), urinary incontinence (Zinner et al., 2004), headache (Colombo et al., 2004) and neuropathic pain (Maizels and McCarberg, 2005). Previous studies have shown that use of antidepressants have even gone beyond the approved and clinically accepted off-label indications (Volkers et al., 2005). Given the different diseases and symptoms that the antidepressants can be prescribed for and the vast amount of research that has been done on antidepressant drug use (Bingefors et al., 1996, Joffe et al., 2001, Hemels et al., 2002, Barbui et al., 2003, Hansen et al., 2003, Rahimtoola et al., 2003, Helgason et al., 2004, Meijer et al., 2004) it is of interest to investigate the indications for antidepressant drug prescription. Information on how the antidepressants are being prescribed for the different symptoms and illnesses could help us in better understanding and interpreting results from prescription database studies done on antidepressant drug use e.g. where antidepressant drug use is set as a proxy for treatment of depression.
When identifying indication for antidepressant drug prescribing using general practice databases it is important that the indication is registered in the physician–patient contact file when a prescription is given. Not registering the indication for prescribing might occur in different situations e.g. for new users where antidepressant drug therapy can be initiated before the general practitioner has come to a diagnosis. To try to overcome these problems time windows of different length around prescription date can be applied. By applying this method more physician–patient contact moments are used to identify the indication for prescribing.
The aim of this study is to investigate for which indications antidepressants are being prescribed in general practice in the Netherlands. In addition, we will investigate how using different time windows around prescription date will influence identifying indications for antidepressant drug prescribing in a general practice database.
Section snippets
Setting and study population
Data of this study were obtained from the Second Dutch National Survey of General Practice (DNSGP-2) which was carried out in 2001 by the Netherlands Institute for Health Services Research (NIVEL) and has been described in detail elsewhere (Westert et al., 2005). In short, 195 general practitioners (GPs) in 104 practices registered details of all physician–patient contacts during 12 months in a standardized way. GPs were trained during an intensive course on coding practices and problems by the
Results
General characteristics of the study population are presented in Table 1 along with the four most frequently prescribed antidepressants. The study population was mainly female (68.7%) with a mean age of 50.8 years. The four most frequently prescribed antidepressants within our study population were the same as the four most frequently used antidepressants in the general Dutch population (Anon, 2005).
Indications for antidepressant prescribing in 2001 in general practice identified when using a
Discussion
Our study shows that depression is the most common indication for antidepressant drug prescribing in general practice. About 45% of the antidepressant drug users had the antidepressant indicated for treating depression which is a bit lower in proportion than what has been reported in earlier studies done in the Netherlands in 1994/95 (de Waal et al., 1996) and in 1996 (Egberts et al., 1998). In addition, our study shows that the proportion of antidepressant drug users with the indication
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