Indications for antidepressant drug prescribing in general practice in the Netherlands

Abstract

Background

The intensity of the use of antidepressants in large populations can nowadays relatively easily be estimated using databases encompassing prescription data. There are shortcomings when using prescription databases as they contain no clinical data on patient illness. Antidepressants are prescribed for different illnesses, thus information on the indications could help when interpreting results from database studies on antidepressant drug use. The aim of this study is to investigate for which indications antidepressants are being prescribed in general practice in the Netherlands.

Methods

Data were obtained from the Second Dutch National Survey of General Practice, carried out by NIVEL (N = 385,461). Patients, 18 years and older, who received an antidepressant prescription from a general practitioner in 2001 were selected (N = 13,835). Indications for antidepressant drug prescribing were identified using time windows of different lengths.

Results

Antidepressants are most often being prescribed for depression (45.5%) and anxiety/panic disorders (17.2%). For these indications lengthening the time window around prescription date from 0 to 180 days resulted in an increase of 20–40% in antidepressant drug users identified with these indications.

Limitation

None of our selected indications could be identified in the physician–patient contact file for about a third of the antidepressant drug users. The study was performed in a general practice setting and did not include antidepressant users who consult psychiatrists.

Conclusion

GPs prescribe antidepressants predominantly for treating depression. However, using antidepressant drug as a proxy for identifying depressed patients in a prescription database should be done with caution and when possible in combination with clinical data.

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.