What drugs are classified as anti depressants? A guide to medication classes

October 12, 2025 •

4 min read

With antidepressants being among the most commonly prescribed medications in the U.S., many people wonder: what drugs are classified as anti depressants?. These medications are grouped into several classes based on their mechanism of action, primarily impacting brain chemistry to help regulate mood.

Quick Summary

Antidepressants are categorized into classes like SSRIs, SNRIs, TCAs, MAOIs, and atypical drugs. They work by altering brain neurotransmitter levels to regulate mood. A healthcare provider determines the most suitable medication based on individual symptoms, other health conditions, and potential side effects.

Key Points

Multiple Classes: Antidepressant drugs are primarily classified into five groups: SSRIs, SNRIs, TCAs, MAOIs, and Atypicals.
Neurotransmitter Impact: Most antidepressants work by increasing the levels of key neurotransmitters like serotonin, norepinephrine, and dopamine in the brain to help regulate mood.
First-Line vs. Later Options: Newer SSRIs and SNRIs are typically first-line treatments due to fewer side effects, while older TCAs and MAOIs are often reserved for treatment-resistant cases.
Diverse Side Effects: The potential side effects of antidepressants vary significantly by class, ranging from mild issues like nausea with SSRIs to more severe interactions requiring dietary restrictions with MAOIs.
Individualized Treatment: The choice of antidepressant is highly personalized and depends on a patient's symptoms, health history, and response to previous medications.
Combined Therapy: The most effective treatment for depression often involves a combination of antidepressant medication and talk therapy.

Understanding the pharmacology of antidepressants

Antidepressants are a diverse group of medications primarily used to treat major depressive disorder and other mental health conditions, such as anxiety, obsessive-compulsive disorder (OCD), and panic disorder. While they don't "cure" depression, they help manage symptoms by targeting key neurotransmitters in the brain, including serotonin, norepinephrine, and dopamine. The classification of these drugs is based on their chemical structure and the specific way they influence these neurochemicals.

Selective Serotonin Reuptake Inhibitors (SSRIs)

SSRIs are the most frequently prescribed type of antidepressant and are often the first-line treatment due to their effectiveness and fewer side effects compared to older classes of drugs.

How SSRIs work

After nerve cells (neurons) release serotonin to communicate, a process called reuptake normally happens, where the serotonin is absorbed back into the original neuron. SSRIs block this reuptake, increasing the amount of serotonin available in the space between neurons (synaptic cleft). This prolonged availability helps improve mood.

Examples of common SSRIs

Citalopram (Celexa)
Escitalopram (Lexapro)
Fluoxetine (Prozac)
Fluvoxamine (Luvox)
Paroxetine (Paxil, Pexeva)
Sertraline (Zoloft)
Vilazodone (Viibryd)

Serotonin and Norepinephrine Reuptake Inhibitors (SNRIs)

Similar to SSRIs, SNRIs are also a newer and common class of antidepressants. They operate by inhibiting the reuptake of both serotonin and norepinephrine. By increasing the levels of these two neurotransmitters, SNRIs can be particularly useful for individuals experiencing both depression and anxiety.

Examples of common SNRIs

Duloxetine (Cymbalta)
Venlafaxine (Effexor XR)
Desvenlafaxine (Pristiq)
Levomilnacipran (Fetzima)

Tricyclic Antidepressants (TCAs)

TCAs are an older class of antidepressants that were developed in the 1950s. They are generally not a first-choice treatment due to a higher risk of side effects and lower safety at high doses compared to newer drugs. However, they can be highly effective for some people, especially those with treatment-resistant depression.

How TCAs work

TCAs block the reabsorption of both serotonin and norepinephrine, similar to SNRIs, but they also affect other neurotransmitters like acetylcholine. This less-selective action is responsible for their broader range of side effects.

Examples of common TCAs

Amitriptyline (Elavil)
Imipramine (Tofranil)
Nortriptyline (Pamelor)
Doxepin (Silenor, Sinequan)
Clomipramine (Anafranil)

Monoamine Oxidase Inhibitors (MAOIs)

MAOIs are one of the earliest types of antidepressants, also introduced in the 1950s. Due to significant dietary restrictions and potential for serious interactions with certain foods (high in tyramine) and other medications, MAOIs are typically reserved for cases of depression that don't respond to other treatments.

How MAOIs work

These drugs inhibit the enzyme monoamine oxidase, which is responsible for breaking down monoamine neurotransmitters (like serotonin, norepinephrine, and dopamine). By blocking this enzyme, MAOIs increase the levels of these neurotransmitters in the brain.

Examples of common MAOIs

Isocarboxazid (Marplan)
Phenelzine (Nardil)
Tranylcypromine (Parnate)
Selegiline (Emsam, a skin patch)

Atypical Antidepressants

This is a broad category for medications that don't fit neatly into the other classifications. Each atypical antidepressant has a unique mechanism of action, and they are often prescribed when other medications are ineffective or cause unwanted side effects.

How atypicals work

Mechanisms vary widely. For example, bupropion (Wellbutrin) inhibits the reuptake of dopamine and norepinephrine, while mirtazapine (Remeron) blocks certain receptors to increase serotonin and norepinephrine.

Examples of common atypical antidepressants

Bupropion (Wellbutrin SR, Wellbutrin XL)
Mirtazapine (Remeron)
Trazodone
Vortioxetine (Trintellix)
Vilazodone (Viibryd)

Comparison of antidepressant drug classes


Class	Mechanism of Action	Common Examples	Common Side Effects	First-Line Treatment?	Special Considerations
SSRIs	Block serotonin reuptake, increasing serotonin levels.	Fluoxetine, Sertraline, Citalopram.	Nausea, sexual dysfunction, insomnia, headache.	Yes.	Fewer side effects than TCAs or MAOIs.
SNRIs	Block reuptake of serotonin and norepinephrine.	Duloxetine, Venlafaxine, Desvenlafaxine.	Nausea, dizziness, dry mouth, sweating.	Sometimes, often after SSRIs fail.	Can also treat chronic pain and anxiety.
TCAs	Block reuptake of serotonin and norepinephrine, and other neurotransmitters.	Amitriptyline, Nortriptyline, Doxepin.	Dry mouth, constipation, drowsiness, blurred vision.	No, typically second-line or for treatment-resistant cases.	More severe side effects; dangerous in overdose.
MAOIs	Inhibit the enzyme monoamine oxidase, increasing monoamine levels.	Isocarboxazid, Phenelzine, Selegiline.	Weight gain, dizziness, sexual dysfunction.	No, reserved for treatment-resistant depression.	Strict dietary restrictions required due to food interactions.
Atypicals	Unique mechanisms (e.g., affect dopamine, serotonin receptors).	Bupropion, Mirtazapine, Trazodone.	Varies greatly by drug; bupropion often lacks sexual side effects.	Used as alternative to SSRIs/SNRIs.	Often tailored to specific side effect profiles (e.g., mirtazapine for insomnia).

How a healthcare provider chooses an antidepressant

Selecting the right antidepressant is not a one-size-fits-all process. It often involves a period of trial and error and close collaboration between a patient and their doctor. Some key factors that influence the decision include:

Specific symptoms: Different antidepressants may target specific symptoms better than others. For example, some may be more effective for insomnia or anxiety.
Side effect profile: A medication's side effects are a primary consideration, as unbearable side effects can lead to non-compliance.
Other health conditions: A person's overall health and pre-existing conditions, such as heart disease or kidney problems, can affect the safety and choice of medication.
Drug interactions: The doctor must consider other medications and supplements being taken to avoid harmful interactions.
Family history: If a close relative had a positive response to a particular antidepressant, that medication might be a good starting point.
Pregnancy status: If pregnant or planning to become pregnant, certain antidepressants may be discouraged.

Conclusion

Antidepressants are categorized into several distinct pharmacological classes, each with a unique mechanism of action and side effect profile. From the widely used SSRIs and SNRIs to the older TCAs and MAOIs, and the diverse group of atypical antidepressants, a range of options exist to manage depressive symptoms. The process of finding the most suitable medication is a collaborative journey between a patient and their healthcare provider, taking into account individual symptoms, health history, and tolerance for side effects. It is crucial to be patient during this process and maintain open communication with your doctor to achieve the best possible treatment outcome. A combination of medication and psychotherapy is often the most effective approach for treating depression.

For more detailed information, consult authoritative health resources, such as the Mayo Clinic's guide on antidepressants.

Frequently Asked Questions

The most commonly prescribed types of antidepressants are Selective Serotonin Reuptake Inhibitors (SSRIs), such as fluoxetine (Prozac) and sertraline (Zoloft), and Serotonin and Norepinephrine Reuptake Inhibitors (SNRIs), like duloxetine (Cymbalta) and venlafaxine (Effexor XR).

Most antidepressants work by influencing the levels of neurotransmitters like serotonin, norepinephrine, and dopamine in the brain. They typically increase the amount of these chemicals available to regulate mood by either blocking their reabsorption into nerve cells or inhibiting enzymes that break them down.

Yes. Different antidepressants may be better suited for certain symptoms. For example, some are more energizing while others are more sedating, which can be useful for patients also experiencing insomnia. The best choice depends on the patient's individual symptom profile.

Common side effects vary by drug class but may include nausea, weight gain, sleepiness, diarrhea, dizziness, dry mouth, and sexual problems. These side effects are often mild and may lessen as the body adjusts to the medication.

Antidepressants typically require 4 to 8 weeks to take full effect. Some people may notice improvements in sleep or appetite sooner, but it can take longer for mood to lift.

TCAs and MAOIs are older classes of antidepressants with more potential side effects and safety concerns than newer drugs. MAOIs also require strict dietary restrictions to avoid dangerous interactions. They are generally reserved for when other treatments have failed.

Atypical antidepressants are a group of medications that do not fit into the other categories because they each have a unique mechanism of action. They can affect various neurotransmitters differently and may be prescribed when other antidepressants are ineffective or produce intolerable side effects.