Antidepressants

Introduction

The following pages contain data on the prescribing of antidepressant drugs, as defined in British National Formulary (BNF)  section 4.3, in Scotland for the financial years 1999/00 to 2008/09, inclusive.  Statistics shown include prescribing volume, as measured by the number of prescribed items and defined daily dose, and the gross ingredient cost, at both Scotland and NHS Board level.  Data on individual drugs are also given.

It should be noted that antidepressant drugs are used for indications other than depression (for example, some types of pain,  sleep disorders and bowel and bladder problems etc.) therefore no guarantee can be given that the statistics relate solely to depression.

Information on depression, its treatment and prevalence, can be found on the following Internet sites:

ISD is not responsible for the contents of external Internet sites

Antidepressant drugs

There are four types of antidepressant drugs, as described in the British National Formulary (BNF)   section 4.3.

• BNF 4.3.1 - TCAs - Tricyclic antidepressants are used to treat depression, as well as having a role to play in the treatment of migraine, panic disorder, obsessive compulsive disorder, recurrent headaches and in the relief of neuropathic pain. 
  
  
• BNF 4.3.2 - MAOIs - Monoamine-oxidase inhibitors are used less frequently than either the tricyclics or Selective Serotonin Re-uptake Inhibitors (SSRIs) and related antidepressants because of the dangers of dietary and drug interactions
  
  
• BNF 4.3.3 - SSRIs - Selective serotonin re-uptake inhibitors are a group of drugs used to treat depression and other conditions such as bulimia, panic disorder and obsessive-compulsive disorder.
  
  
• BNF 4.3.4 - Others - Drugs that do not fit any of the above categories.  For example, Duloxetine inhibits the re-uptake of both serotonin and noradrenaline and is therefore termed a Serotonin and Noradrenaline Re-uptake Inhibitor (SNRI).  Other drugs in this group are Flupentixol (also used in the treatment of psychoses), Mirtazapine, Reboxetine, Tryptophan and Venlafaxine.

HEAT Indicator

The Scottish Government have sponsored a new range of target indicators for NHS Scotland under the title of Health improvement, Efficiency, Governance, Access to services and Treatment appropriate to the individual (HEAT). The objective of the antidepressant target is to stop the increase.

Summary

The prescribing of antidepressant drugs in Scotland between 1999/00 & 2008/09 has been analysed.  A summary of the findings is given below:

• A total of 4.01 million items were prescribed in Scotland during 2008/09, an increase of 178,650 from the previous financial year. 
  
  
• The annual rate of increase in the prescribing of antidepressant drugs is falling, down 9.5% in 1999/00 to 4.7% in 2008/09.
  
  
• The gross ingredient cost of antidepressant drugs in 2008/09 was £35.8m, down from £40.5m in the previous financial year.  The decrease is attributable to a number of drugs being reduced in price.
  
  
• The average cost per defined daily dose (DDD), as a consequence of the above, fell from 0.23p in 2007/08 to 0.22p 2008/09, equivalent to £85 per annum.
  
  
• It is estimated 9.7% of the Scottish population aged 15 and over make daily use of antidepressant drugs.
  
  
• Prescribing of Tricyclics, SSRIs and 'Other Antidepressants',  increased by 3.7%, 3.8% and 9.8% respectively in 2008/09, MAOI prescribing fell by 4.8%.
  
  
• Top five drugs in volume terms were, Amitriptyline, Fluoxetine(Prozac^®), Citalopram (Cipramil^® ), Mirtazapine(Zispin SolTab^®) and Venlafaxine (Efexor^® ).
  

Data Source

Practitioner Services , a division of NHS National Services Scotland, processes all NHS prescriptions for payment of pharmacies, dispensing doctors and appliance suppliers.  This gives a full record from which trends in prescribing can be investigated at a detailed level.  The data includes prescribing by GPs, nurses, dentists, pharmacists and hospitals, where the latter was dispensed in the community.  Hospital dispensed prescriptions are NOT included in the figures.  Information Service Division (ISD) cannot say what proportion of the drug dispensed is actually consumed.

An Excel File  is provided that gives both the data behind the graphs and for individual drugs in BNF section 4.3, the antidepressants.  The file also contains historic data between 1992/93 and 1998/99.  The file contains three pivot tables showing number of prescribed items, gross ingredient cost and defined daily doses respectively for each year, by BNF section and individual drug.  The WHO defined daily does value for each drug is also provided in this file.

Figure 1 shows the number of prescribed items in total and by type for antidepressant drugs prescribed in Scotland from 1992/93 to 2007/08. 

Figure 1 - Number of prescribed items - Scotland 1999/00 to 2008/09



Source: Prescribing Information System, ISD Scotland

Although there is a rise in prescribing of antidepressants, the annual rate of growth is decreasing, down from 4.7% in 2007/08 to 3.6% in 2008/09.  Prescribing of antidepressant drugs in England follows the same trend, the rate decreasing from 9.0% in 2007 to 6.3% in 2008 (calendar years).

Prescribing of the Tricyclic, SSRI and 'Others' increased by 3.7%, 3.8% and 9.8% respectively, compared to 1.6%, 5.6% and 8.8% increase for 'Other antidepressants' in the previous year.  In contrast prescribing of MAOIs declined by 4.8%. 

ISD cannot say from this data how many people are receiving these drugs.  However, an approximation can be found from using the defined daily dose (DDD)  as developed by the World Health Organisation (WHO)  .  The DDD is defined as:

 "... the assumed average maintenance dose per day for a drug
                                                                      used in its main indication in adults" . 

DDDs are derived from the international use of the substance in question.  As British prescribing patterns may differ from the accepted international value, each DDD should be regarded as a technical value, a close approximation of an average of the actually used doses.  The DDDs are therefore not necessarily the most frequently prescribed or used doses. 

This approach has the advantage of eliminating problems associated with prescribed items (variation in amount prescribed, differing formulations) and gross ingredient cost (price variation over time and price difference between products).

WHO defined daily dose values for drugs within BNF section 4.3 are given in a downloadable Excel File

Figure 2 shows the defined daily dose given as the number of DDDs per 1,000 population per day.   This value offers an explanation of what proportion of the population may receive a certain drug treatment.  For example, an estimated drug consumption of 10 DDDs/1000 population/day corresponds to a daily use of the drug by 1% of the population.  The population used is the mid-year estimates produced by the General Register Office for Scotland , but restricted to persons aged 15 and over. 

Figure 2 - Number of DDDs per 1000 population (aged 15+) per day 1999/00 to 2008/09



Source: Prescribing Information System, ISD Scotland

The prescribing pattern exhibited in Figure 2 is similar to that of figure 1, with both SSRIs and Tricyclics being the main choice of antidepressant by prescribers.  Daily use of antidepressants has grown from 5.4% in 1999/00 to 9.7% (419,737 adults) of the population (aged 15+) by 2008/09.  It should be emphasised that these figures are estimates, the actual patient base is unknown.

The gross ingredient cost, that is the cost of the drug before the deductions of any supplier discount and patient charges, is given in figure 3. 

Figure 3 - Gross Ingredient Cost (£) of antidepressant drugs - 1999/00 to 2008/09



Source: Prescribing Information System, ISD Scotland

The total gross ingredient cost of antidepressant drugs during 2008/09 was £35.8 million, down £4.7 million from the previous year.  This is attributable to a reductions in price for some of the drugs.  By type the SSRIs contributed £9.9 million, 'Others'  £17.9 million, Tricyclics £7.8 million and MAOIs £0.2 million to the total bill.   Figures for the previous year were £11.9m, £17.6m, £10.8m and £0.2m respectively.

The cost per defined daily dose (DDD) for 2008/09 is £0.23 or £85 per annum, down from £0.28 (£101 per annum).  Taking the GRO mid-year population estimate for 15 and over, the cost per head is calculated as £8.29 in 2008/09, down from £9.43 in the previous financial year. 

Prescribing Statistics - NHS Boards

a) Usage
 The following charts, for reasons of clarity, use the NHS Board cipher rather the board name.  Table 1 maps the cipher to the Board name. 

Please note that NHS Argyll and Clyde ceased to exist as a single entity from April 2006.  Argyll and Bute was absorbed into NHS Highland and the remainder into NHS Greater Glasgow to become NHS Greater Glasgow and Clyde.

Table 1 - NHS Board cipher and name

The number of DDDs per 1,000 population aged 15 and over has been used to permit comparison in dispensing of antidepressant drugs between NHS boards, as shown in Figure 4. 

Figure 4 - DDDs per 1000 population (aged 15+) per day - by NHS Board 1999/00 to 2008/09



Source: Prescribing Information System, ISD Scotland

The percentage of the population in 2007/08 'using' antidepressants daily varies from 7.1% in Shetland (Z) to 11.2% in Greater Glasgow and Clyde (G).  Five boards are above the Scottish average (9.7%):

• 11.2% - Greater Glasgow (G)
• 10.8% - Ayrshire and Arran (A)
• 10.7% - Lanarkshire (L)
• 9.9% - Forth Valley (V)
• 9.9% - Tayside (T)

It should be noted that these figures are estimates; the actual patient base is unknown.

b) Costs
Figure 5 shows that the gross ingredient cost for antidepressant drugs per head of population has increased from an average of £10.78 in 1999/00 to £8.29 by 2008/09

Figure 5 - Gross Ingredient Cost (£) per head of population (aged 15+)
by NHS Board 1999/00 to 2008/09



Source: Prescribing Information System, ISD Scotland

Increased cost over time are driven not only by increased prescribing (figure 1), but through changes in prescribing pattern, that is, increased use of newer, more expensive drugs.  Between 1999/00 and 2008/09 the following changes occurred:

• Tricyclics increased by 11.1%, up from 1,123,482 to 1,248,329 prescriptions
• MAOIs fell by 30.8%, down from 13,706 to 9,486 prescriptions  
• SSRIS increased 1.5 fold, up from 1,373,302 to 2,113,910 prescriptions
• 'Other' increased more than 21 fold, up from 29,252 to 634,012 prescriptions

Drugs contributing to increased SSRI prescribing are Fluoxetine (Prozac^®) and Citalopram (Cipramil^® ) and for 'Other', Venlafaxine (Efexor^®).   

Prescribing Statistics - Drugs

The top five antidepressant drugs prescribed in Scotland, in terms of the number of items, are:

Figure 6 - Top five antidepressant drugs prescribed in Scotland 1999/00 to 2008/09



Source: Prescribing Information System, ISD Scotland

Figure 7 gives the usage of the top five antidepressants in terms of the number of DDDs per 1000 population per day.

Figure 7 - Top five drugs - DDDs per 1000 population (aged 15+) per day 1999/00 to 2008/09



Source: Prescribing Information System, ISD Scotland

Four of the top 5 drugs show an increase (figure 6), between 2007/08 and 2008/09. Citalopram shows the biggest increase in 111,982 items and Fluoxetine has decreased by 10,878 items.  The top 5 drugs in 2008/09 are the same as top 5 drugs in 2007/08.  Venlafaxine has declined in 2006/07, probably due to adverse publicity, e.g. BBC Panorama  , regarding addiction fears and unpleasant withdrawal symptoms.

Concerns were raised in December 2004 about potential for cardiotoxicity and toxicity in overdose with Venlafaxine.  The Medicines and Healthcare Regulatory Agency (MHRA)  issued guidelines restricting use of Venlafaxine to specialist initiation and contraindications in patients with heart disease; with an adverse effect on prescribing.   New guidelines issued in May 2006 saw these restrictions being largely lifted.

Data displayed in figure 7 indicate that daily use is made of:

• Amitriptyline by an estimated 1.05% of the population
• Fluoxetine by an estimated 2.13% of the population
• Citalopram by an estimated 2.51% of the population
• Mirtazapine by an estimated 0.70% of the population
• Venlafaxine by an estimated 0.73% of the population

Figure 7 shows an anomaly where Amitriptyline exhibits a lower growth rate than that displayed in figure 6.  The number of DDDs per prescription, a function of quantity and tablet strength, has dropped from 24.9 DDDs in 1999/00 to 21.1 DDDs by 2008/09. This indicates either a reduction in dosage for its main licensed indication or increased prescribing for indications other than depression, where a lower dose is normally given, such as the relief of neuropathic pain, an unlicensed indication.

Figure 8 shows that the number of scripts issued for 10mg Amitriptyline tablets has increased from 17.7% of prescribed itemsin 1999/00 to 39.5% by 2008/09.  At the same time prescribing of the 25mg Amitriptyline tablets declined from 53.2% to 38.3% of prescribed items. Prescribing of 50mg tablets has remained almost constant throughout the period at ~25%, until 2008/09 where is has dropped to 21.6%.  It could be inferred, therefore, that a change in practice has occurred with Amitriptyline being used to treat other indications.  The data is, however, insufficient to arrive at a definitive conclusion.

Figure 8 - Amitriptyline - Comparison of prescribed strength 10 & 25mg tablets 1999/00 to 2008/09



Source: Prescribing Information System, ISD Scotland

Main contact: Prescribing Team

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