Difference Between SNRI and SSRI

Main Difference – SNRI vs SSRI

SNRI (serotonin-norepinephrine reuptake inhibitors) and SSRI (selective serotonin reuptake inhibitors) are two classes of drugs used in the treatment of depression and anxiety disorders. Both types of drugs inhibit the reuptake of neurotransmitters such as serotonin and norepinephrine by the nerve cells in the brain, elevating the mood and increasing the energy levels in the body. Hence, both SNRI and SSRI can be considered as antidepressants. The main difference between SNRI and SSRI is that SNRI can be used to treat chronic nerve pains whereas SSRI is used to treat depression and anxiety. Both types of drugs take about few days to weeks to produce the effect of the drug. However, both SNRI and SSRI do not show any drug addiction effects.

Key Areas Covered

1. What is SNRI
     – Definition, Mechanism of Action, Side Effects
2. What is SSRI
     – Definition, Mechanism of Action, Side Effects
3. What are the Similarities Between SNRI and SSRI
     – Outline of Common Features
4. What is the Difference Between SNRI and SSRI
     – Comparison of Key Differences

Key Terms: Antidepressants, Brain, Depression, Norepinephrine, Serotonin, SNRI (Serotonin-Norepinephrine Reuptake Inhibitors), SSRI (Selective Serotonin Reuptake Inhibitors)

What is SNRI

SNRI (serotonin-norepinephrine reuptake inhibitors) refers to an antidepressant medicine that acts upon the neurotransmitters of the brain used to treat depression and chronic pain. It inhibits the reuptake of both serotonin and norepinephrine by the nerve cells in the brain. Both serotonin and norepinephrine are associated with positive feelings. Norepinephrine is more specifically associated with alertness and energy. Therefore, SNRI drugs can be used to treat major depressive disorders anxiety disorders, mood disorders, and ADHD (attention deficit hyperactive disorder). In addition, SNRI is used in the treatment of chronic neuropathic pains such as nerve pain associated with fibromyalgia, diabetes, and menopause. The depression cycle and the effects of an antidepressant are shown in figure 1.

Figure 1: Depression Cycle

Side Effects

SNRI causes more side effects than SSRI. Those side effects are the emergence of suicidal thoughts, breathing problems, sleeping problems, hives, increased risk of bleeding along with weight loss. It is also less tolerated than SSRI. The side effects can develop into withdrawal symptoms such as insomnia and dizziness with discontinued abruptly.

What is SSRI

SSRI (selective serotonin reuptake inhibitors) refers to the antidepressant that inhibits the reuptake of serotonin by the nerve cells of the brain. Well-being and joy are associated with serotonin. The amount of serotonin available in the brain is increased once the reuptake of serotonin is inhibited by SSRI. This increases the neurotransmitter levels in the synaptic cleft, decreasing the firing of neurons. Hence, SSRI can be used to treat moderate to severe depression. It can also be used to treat anxiety disorders, panic disorders, OCD (obsessive-compulsive disorder, and PTSD (post-traumatic stress disorder). The action of neurotransmitters in the synaptic cleft is shown in figure 2.

Figure 2: Action of Neurotransmitters in the Synaptic Clef

Side Effects

Though the side effects of SSRI are less severe than SNRI, immediate attention is required as it may give rise to suicidal thoughts, agitation, increased risk of bleeding, and erectile dysfunction.

Similarities Between SNRI and SSRI

• SNRI and SSRI are two types of antidepressant drugs used in the treatment of depression and anxiety disorders.
• Both SNRI and SSRI act upon the neurotransmitters of the brain.
• Both SNRI and SSRI inhibit the reuptake of neurotransmitters such as serotonin and norepinephrine by the nerve cells in the brain, elevating the mood and increasing the energy levels in the body.
• Both SNRI and SSRI take about few days to weeks to produce the effect of the drug.
• Both SNRI and SSRI do not show any drug addiction effects.
• Both SNRI and SSRI should not be stopped abruptly without medical advice.

Difference Between SNRI and SSRI

Definition

SNRI: SNRI refers to an antidepressant medicine that acts on the neurotransmitters of the brain that affect a person’s mood.

SSRI: SSRI refers to the antidepressant that inhibits the reuptake of serotonin in the brain.

Type of Neurotransmitters They Act on

SNRI: SNRI inhibits the reuptake of both serotonin and norepinephrine.

SSRI: SSRI inhibits the reuptake of serotonin.

Types of Disorders

SNRI: SNRI drugs can be used to treat major depressive disorders anxiety disorders, mood disorders, and ADHD (attention deficit hyperactive disorder).

SSRI: SSRI can be used to treat moderate to severe depression, anxiety disorders, panic disorders, OCD (obsessive-compulsive disorder), and PTSD (post-traumatic stress disorder).

Side Effects

SNRI: SNRI causes more complicated side effects than SSRI.

SSRI: SSRI causes less severe side effects.

Toleration

SNRI: SNRI is less tolerant.

SSRI: SSRI is more tolerant than SNRI.

Cost

SNRI: SNRI is more cost-effective.

SSRI: SSRI is less cost-effective.

Conclusion

SNRI and SSRI are two types of drugs used to treat depression and anxiety. Both types of drugs inhibit the reuptake of serotonin and norepinephrine, the neurotransmitters responsible for positive feelings. SNRI can also be used to treat chronic neuropathic pains. The main difference between SNRI and SSRI is their role in the treatment of depression and pain.

Reference:

1. Thase, M E. “Are SNRIs more effective than SSRIs? A review of the current state of the controversy.” Psychopharmacology bulletin., U.S. National Library of Medicine, Available here.

Image Courtesy:

1. “Depression Cycle” By No machine-readable author provided. Webber assumed, Own work assumed (based on copyright claims). (Public Domain) via Commons Wikimedia
2. “Figure 09 01 02” By CNX OpenStax – (CC BY 4.0) via Commons Wikimedia