Selective Serotonin Reuptake Inhibitors (SSRIs)

SSRIs, or selective serotonin reuptake inhibitors, are the most commonly prescribed antidepressants in the U.S. As their name suggests, SSRIs are used to treat depression.

SSRIs are believed to improve mood and treat depression by increasing serotonin levels in the brain.

List of SSRIs

Below is a list of SSRIs currently prescribed in the U.S.:

• Celexa (citalopram)
• Lexapro (escitalopram)
• Paxil, Paxil CR, Pexeva (paroxetine)
• Prozac (fluoxetine)
• Zoloft (sertraline)
• Trintellix (vortioxetine)
• Viibryd (vilazodone)

Luvox (fluvoxamine) is no longer available in the U.S. However, it is still available under the generic names, fluvoxamine and nefazodone.

FDA-Approved Uses

In addition to depression, SSRIs are FDA-approved to treat the following mental health conditions in adults, including:

• Generalized anxiety disorder (GAD)
• Major depressive disorder (MDD) 
• Obsessive-compulsive disorder (OCD)
• Panic disorder (PD)
• Post-traumatic stress disorder (PTSD)
• Premenstrual dysphoric disorder (PMDD)
• Social anxiety disorder (SAD)

SSRIs are also the first-line medication option for young people with depression and anxiety. The table below lists the FDA-approved uses for individual SSRIs.

As you can see, every SSRIs is not FDA-approved to treat every mood-related disorder. For example, although Paxil and Zoloft are the only medications approved by the FDA for PTSD, doctors may prescribe Prozac off-label.

Off-Label Uses

If your doctor prescribes a medication for a purpose other than what it has been approved to treat, this is called "off-label" prescribing.

Doctors may also prescribe SSRIs off-label to treat a broad range of other conditions, including:

• Disordered eating
• Fibromyalgia
• Migraines
• Premature ejaculation

The potential downside of prescribing SSRIs off-label is that doctors won't know about possible risks when they are used by people who are not depressed.

Precautions and Contraindications

SSRIs are not for everyone and must be used with caution in certain individuals.

Pregnant Women

Hundreds of studies have looked at SSRI exposure and birth defects. With the exception of Paxil, most SSRIs are generally considered safe to use during pregnancy. But they are not without risk.

• Birth defects: SSRI use during pregnancy may increase the risk of abdominal, heart, and lung birth defects.
• Blood loss after childbirth: Some studies have reported a slightly higher risk of postpartum hemorrhage among women on SSRIs.
• Miscarriage or premature birth: Pregnant women on antidepressants are at increased risk for a number of complications, including miscarriage and premature delivery.
• Psychiatric disorders in children: Children of mothers who used antidepressants before and during pregnancy have a higher risk of developing a psychiatric disorder. However, this association may be attributable to the severity of the mother’s underlying condition.
• Withdrawal symptoms in newborns: Newborns exposed to SSRIs in the last trimester may experience withdrawal symptoms. The most common withdrawal symptoms are tremors, disturbed sleep, and high-pitched crying.

Letting depression go untreated can also have a negative impact on a pregnancy. Remember to always weigh the risks of SSRI treatment to the risks of untreated depression.

Breastfeeding Women

It's possible that SSRIs can be passed to your baby through your breastmilk. If you're pregnant (or trying to become pregnant) trying to choose an antidepressant for which there are data to support its safety during breastfeeding. 

The relative infant doses are close to 10% and in some cases even above 10% for citalopram, fluoxetine and venlafaxine.

The relative infant doses are below 10% for Lexapro, Paxil, and Zoloft.

Zoloft, Paxil, and Prozac have been widely studied and are considered relatively safe for use during breastfeeding. The data suggest that the amount of these drugs nursing infants are exposed to is low enough that they don't lead to adverse effects.

Children

In 2004, the FDA issued a black box warning—the agency's strictest warning—that young people (up to age 25) taking antidepressants might experience increased suicidal thoughts and behaviors.

The warning also says that children and adolescents taking SSRIs should be carefully watched for sudden changes in their mood or actions, such as:

• Aggressive or hostile behavior
• Extreme increase in movement and talking
• Making suicidal statements
• Trouble sleeping
• Withdrawal from friends and family

If you see any of these signs in your child, particularly if they are new or noticeably worse than before, be sure to talk to your doctor as soon as possible.

Side Effects

As a whole, SSRIs are considered the most effective antidepressants with the fewest side effects. The majority of people who take them experience at least one side effect. Most of them are minor and usually go away as your body gets used to the medication.

Common side effects of most SSRIs include:

• Diarrhea
• Drowsiness
• Dry mouth
• Headache
• Increased sweating
• Insomnia
• Nausea and vomiting
• Sexual dysfunction (ejaculation failure and decreased libido)
• Weight gain

Ask your doctor to explain all the known side effects of your chosen SSRI. If you're experiencing one or more of these side effects, talk to your doctor. They may be able to suggest ways to lessen them.

Serotonin Syndrome

SSRIs aren't the other medications that increase serotonin levels in your body. Other medications, such as pain medications, certain migraine medications, and herbal supplements, can also increase serotonin levels.

Taking two or more of drugs that increase serotonin levels in your body (serotonergic drugs) can lead to a condition called serotonin syndrome. Examples of serotonergic drugs include pain medications, certain migraine medications, herbal supplements (such as St. John's wort), and of course, antidepressants.

If too much serotonin builds up in your body you may experience some of the following symptoms of serotonin syndrome:

• Autonomic effects: Abnormally fast heart rate, hypertension, hyperthermia, shivering, sweating
• Mental status effects: Confusion, delirium, excitement, restlessness, and hallucinations.
• Neuromuscular effects: Muscle twitching, tremor, and increased reflexes.

Though rare, serotonin syndrome may be life-threatening if not treated immediately.

Discontinuation Syndrome

SSRIs work by altering the levels of neurotransmitters—the chemical messengers that attach to neurons throughout the body and influence their activity.

Neurons eventually adapt to the current level of neurotransmitters. If the level changes too much too fast, for example because you've suddenly stopped taking your antidepressant—it can lead to uncomfortable withdrawal symptoms.

• Feeling anxious
• Flu-like symptoms
• Hyperarousal
• Nausea
• Sensory disturbances
• Trouble sleeping

Symptoms occur within two to four days after drug cessation and usually last one to two weeks.