Treatment of Panic and Anxiety Disorders: SSRIs and SNRIs

Serotonin and SSRIs

Serotonin is a chemical known as a neurotransmitter, which is what brain cells use to communicate signals affecting a wide variety of body functions. Low serotonin levels are linked to anxiety and depression. Serotonin has been described as the “feel good” brain chemical. Serotonin cannot cross into the brain from the body’s circulating blood, so all serotonin used inside the brain must be produced by the brain.  

Selective serotonin reuptake inhibitors (SSRIs) are the most commonly prescribed medications for the treatment of depression, anxiety, and other mood disorders. SSRIs prevent brain cells from reabsorbing serotonin, raising the level of serotonin available in the synapses, or the space between the cells. This makes it easier for the brain cells to communicate with each other and with the body, which may result in elevated, more stable moods.   

SSRIs were first approved by the FDA in the 1980s and continue to be the most popular option for the treatment of depression and anxiety. SSRIs (and their brand names) include:

• Citalopram (Celexa)
• Escitalopram (Lexapro)
• Fluoxetine (Prozac)
• Fluvoxamine (Luvox)
• Paroxetine (Paxil)
• Sertraline (Zoloft)

Norepinephrine and SNRIs

Norepinephrine is a chemical that functions as both a hormone and a neurotransmitter. Along with other “fight or flight” hormones, norepinephrine helps the body respond to stressful situations by increasing energy levels. It affects blood pressure, heart rate, and the metabolism of fat and sugar. In the brain, norepinephrine impacts sleep cycles, memory storage, and the ability to focus. Low or erratic norepinephrine levels have been linked to depression, panic attacks, and attention deficit hyperactivity disorder (ADHD).  

Serotonin-norepinephrine reuptake inhibitors (SNRIs) are medications that work by preventing the reabsorption of both serotonin and norepinephrine in the brain. This improves the signaling from the brain cells to impact mood, concentration, and a variety of body functions. SNRIs also may help relieve some types of chronic pain.  

SNRIs were first approved by the FDA in the 1990s and are a popular choice for the treatment of depression, anxiety, panic disorder, or chronic pain. SNRIs (and their brand names) include: 

• Desvenlafaxine (Pristiq)
• Duloxetine (Cymbalta)
• Levomilnacipran (Fetzima)
• Milnacipran (Savella)
• Venlafaxine (Effexor)

Uses of SSRIs and SNRIs

Selective serotonin reuptake inhibitors (SSRIs) and serotonin-norepinephrine reuptake inhibitors (SNRIs) both belong to the general class of medications known as antidepressants. The term “antidepressants” is confusing because these medications are not exclusively used to treat depression. The FDA has approved each SSRI and SNRI for different uses. Some examples of SSRI uses include:

• Depression (major depressive disorder) and related illnesses such as post-partum depression and premenstrual dysphoric disorder
• Generalized anxiety disorder and related anxiety disorders such as phobias and social anxiety
• Panic disorder
• Post-traumatic stress disorder (PTSD)
• Obsessive-compulsive disorder (OCD) and eating disorders
• Bipolar disorder

In addition to the uses for SSRIs, SNRIs may also be used to treat chronic muscle, joint, or nerve pain. It is also prevalent for SSRIs and SNRIs to be prescribed “off label” for a reason other than its FDA-approved use based on evidence from studies or from or a prescribers’ experience.  

What to Expect When Taking SSRIs or SNRIs

Before starting an SSRI or SNRI, it is essential to understand that these medications do not take immediate effect. In general, SSRIs and SNRIs take 1 to 2 weeks to begin to increase neurotransmitter levels in the brain. Be aware that anxiety symptoms may worsen before they get better. Allow at least 4 to 8 weeks of treatment before evaluating the effectiveness of the medication. It is crucial to view starting an antidepressant as a commitment. The drug should be taken around the same time every day. These medications will not work if they are taken sporadically and or if taken “as needed” for panic attack symptoms.

Most SSRIs and SNRIs are generally well-tolerated, and some of the most common side effects, such as nausea or tiredness, are transient. This means that they usually fade after the first few weeks as the body adjusts to taking the medication. Taking medication with food can reduce nausea. Common side effects of SSRIs and SNRIs include:

• Blurred vision
• Dizziness
• Drowsiness
• Dry mouth
• Stomach upset (constipation, diarrhea, nausea)
• Headache
• Sexual problems (reduced desire or erectile dysfunction)
• Appetite changes (resulting in weight gain or loss)

Individual results can vary. If a person cannot tolerate one SSRI or SNRI, they may be able to tolerate a different one, even from the same category. 

SSRIs and SNRIs are generally considered the safest types of antidepressant treatment for most people. However, there are a few safety concerns to be aware of before starting an antidepressant.

Drug Interactions

During discussions with healthcare providers, it is important to disclose all medications so that the safest antidepressant can be selected. Other prescription drugs, over-the-counter medications, and herbal supplements may pose a severe danger when taken in combination with certain antidepressants. SSRIs may increase the risk of stomach ulcers, especially when taken with other medications that increase bleeding risk, such as nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen or aspirin.

Serotonin Syndrome

While very rare, it is possible that SSRIs or SNRIs can cause serotonin levels to go too high. The risk of serotonin syndrome is increased when an individual is taking more than one medication that boosts serotonin. These may include taking more than one antidepressant, some pain or migraine medications, some ADHD treatments, or herbal supplements such as St John’s Wort. Signs of serotonin syndrome include high fever, agitation, sweating, shaking, restlessness, and heart racing. It is crucial to seek immediate medical attention if symptoms of serotonin syndrome occur.        

Suicide Risk

The FDA requires all antidepressants to come with a black box warning regarding an increase in suicide risk, especially in children, adolescents, and young adults under 25 years old. Children and young adults should be monitored carefully for suicidal behaviors in the first several weeks of treatment, and after dose increases.  

Stopping SSRIs and SNRIs

SSRIs and SNRIs are not habit-forming or addictive. However, missing doses or stopping treatment abruptly can cause withdrawal-like symptoms. Withdrawal-like symptoms may include nausea, lack of energy, dizziness, headache, and generally feeling “off.” It is best to wean off SSRIs and SNRIs gradually after discussing with a healthcare professional such as a physician or pharmacist.  

Finding the Best Treatment for Anxiety or Depression 

It may take trial-and-error to find the SSRI or SNRI that works for each individual. Every person is different, and their response to treatment varies. Finding the right medication may take several months and even longer until the proper dosage is adjusted. Sometimes, other medications have to be added to help manage the side effects of SSRIs or SNRIs.

Anxiety and depression are real diseases. Like other diseases, medication alone is usually not enough. Talking to a therapist, joining support groups, and learning coping skills can help along with taking medications as prescribed. Coping skills include self-care such as regular exercise, healthy food choices, and getting adequate sleep. With an abundance of effective treatment options available, there is no reason to suffer in silence. Talking to a trusted friend, doctor, or pharmacist can be the first step in getting help for anxiety or depression.