Last reviewed 2026-04-19 · How we verify

Nardil (Phenelzine Sulfate)

Phenelzine Sulfate (Nardil), marketed by Pfizer, is a monoamine oxidase inhibitor (MAOI) primarily indicated for atypical depression, with a key composition patent expiring in 2028. Its mechanism of action, which increases levels of serotonin and norepinephrine, provides a unique therapeutic profile for patients who do not respond to other antidepressants. However, the presence of off-patent competitors like tranylcypromine, which has three generics available, poses a significant threat to Nardil's market share.

At a glance

Approved indications

• Atypical Depression
• Mixed Anxiety and Depression
• Severe Depression with Endogenous Features

Boxed warnings

• Suicidality and Antidepressant Drugs Antidepressants increased the risk compared to placebo of suicidal thinking and behavior (suicidality) in children, adolescents, and young adults in short-term studies of major depressive disorder (MDD) and other psychiatric disorders. Anyone considering the use of Phenelzine Sulfate Tablets or any other antidepressant in a child, adolescent, or young adult must balance this risk with the clinical need. Short-term studies did not show an increase in the risk of suicidality with antidepressants compared to placebo in adults beyond age 24; there was a reduction in risk with antidepressants compared to placebo in adults aged 65 and older. Depression and certain other psychiatric disorders are themselves associated with increases in the risk of suicide. Patients of all ages who are started on antidepressant therapy should be monitored appropriately and observed closely for clinical worsening, suicidality, or unusual changes in behavior. Families and caregivers should be advised of the need for close observation and communication with the prescriber. Phenelzine Sulfate Tablets is not approved for use in pediatric patients. (See Warnings: Clinical Worsening and Suicide Risk , Precautions: Information for Patients , and Precautions: Pediatric Use )

Common side effects

• Dizziness
• Headache
• Drowsiness
• Sleep disturbances
• Fatigue
• Weakness
• Tremors
• Constipation
• Dry mouth
• Gastrointestinal disturbances
• Weight gain
• Postural hypotension

Drug interactions

• Alpha/Beta Agonists
• Amphetamines
• Indirectly Acting Sympathomimetic Amines
• Selective Serotonin Reuptake Inhibitors
• Serotonin/Norepinephrine Reuptake Inhibitors
• Tricyclic Antidepressants
• almotriptan
• bupivacaine
• buspirone
• dextromethorphan
• dextropropoxyphene
• eletriptan

Key clinical trials

• Precision Care for Major Depressive Disorder (PHASE4)
• Study to Evaluate the Pressor Effect of Oral Tyramine During Ozanimod Treatment in Healthy Adult Participants (PHASE1)
• Efficacy of Hydroxyzine for Patients With Panic Disorder (PHASE4)
• Phenelzine Sulfate in Treating Patients With Non-metastatic Recurrent Prostate Cancer (PHASE2)
• A Study in Healthy People to Test How Combining BI 1467335 and Tyramine Affects Blood Pressure (PHASE1)
• An Early Phase Study of Abraxane Combined With Phenelzine Sulfate in Patients With Metastatic or Advanced Breast Cancer (PHASE1)
• Phenelzine Sulfate and Docetaxel in Treating Patients With Prostate Cancer With Progressive Disease After First-Line Therapy With Docetaxel (PHASE2)
• Drug-drug Interaction Study of Ozanimod With Tyramine to Evaluate the Effect on Pressor Response (PHASE1)

Primary sources

Every claim on this page is sourced from regulatory or scientific primary sources. See our editorial policy for full methodology.

Competitive intelligence

For the full competitive landscape — auto-detected comparators, recent regulatory actions across the set, upcoming PDUFA, patent timeline, sponsor landscape:

• Nardil CI brief — competitive landscape report
• Nardil updates RSS · CI watch RSS
• Pfizer portfolio CI