Case Study in SSNRI

1. Drug Overview

Depression is related to a deficiency in the amount or function of serotonin, norepinephrine and dopamine in the brain. The need for a wide range of antidepressants with different pharmacological profiles, is driven by the diversity of clinical manifestations seen during depressive episodes [1].

Selective Serotonin Reuptake Inhibitors (SSRIs) are considered as first line treatment in depression, with Selective Serotonin Noradrenaline Reuptake Inhibitors (SSNRIs) prescribed in patients, where SSRIs are ineffective [1].

SSRIs have a single function, whereby they increase the levels of serotonin in the brain by limiting its reabsorption, though some SSRIs do show a weak affinity for norepinephrine and dopamine [1].

SSNRIs, increase serotonin and norepinephrine throughout the brain, as well as increasing dopamine in the prefrontal cortex [2].

In addition to their use in depression, SSRIs and SSNRIs are also effective in the treatment of [1] [3]:

Major Depressive Disorder
Generalized Anxiety Disorder
Diabetic Peripheral Neuropathy
Fibromyalgia
Chronic Musculoskeletal Pain

2. Market Overview

The market data below (see Figure 1), focuses mainly on the N06A5 class (SSNRIs) and the shifts in market share as a result of the launch of Duloxetine O in 2004. There were significant macroeconomic changes in the pharmaceutical industry during (and before) its launch.

At the time of its launch, the SSNRI market consisted of two products; Duloxetine O and Venlafaxine O, which was launched in the mid-1990s. The first venlafaxine generic was launched in 2006, followed by another six venlafaxine generics (Venlafaxine G) between 2009 – 2012. The launch of the first duloxetine generic (clone – Duloxetine C) was in 2009, followed by a single generic (Duloxetine G) in 2013.

3. Health Status

Depression is a common but serious mood disorder that affects a person’s behaviour, feelings, thoughts and sense of well-being [4]. Nearly 1:3 South Africans will suffer from a mental disorder in his/her lifetime.

The burden of mental disorders has grown over the past 20 years (1990 – 2010), with major depressive disorder rising in the Top 25 ‘Causes of Disability’ rankings from 15^th to 11^th over the period [5], with a lifetime prevalence of 9.8 % [6][7].

There is still a treatment gap of 75%, with only 25% of people with common mental disorders receiving treatment of any kind [8].

This rise is expected to last, partly due to the ongoing epidemiological transition from communicable to non-communicable diseases, and co-morbidities between HIV and chronic health conditions [6]. Major depressive disorder is also comorbid with a variety of psychiatric conditions [9].

At the time of this report, depression was not yet a Prescribed Minimum Benefit (PMB), and minimal benefits are allocated to depression (including Major Depressive Disorder).

In 2004, Bipolar Disorder was listed as a PMB. Thus, patients with Major Depressive Disorder (subtly different from Bipolar Disorder II) are sometimes classified as Bipolar II, in order to be able to access chronic medicines.