Tranylcypromine Side Effects: What to Expect and When to Call Your Doctor

Tranylcypromine (Parnate) is a powerful antidepressant in the MAOI class. For the right patient, it can be transformative — but it comes with a set of side effects that are more complex and serious than most antidepressants. Being informed about what to expect can help you manage common side effects effectively and recognize serious ones before they become dangerous.

Common Side Effects of Tranylcypromine

The most frequently reported side effects of tranylcypromine include:

Insomnia — The most common side effect. Often managed by taking the last dose no later than 3 PM to reduce stimulant-like effects at night.

Dizziness and orthostatic hypotension — A drop in blood pressure when standing up quickly (postural hypotension) is common, especially at doses above 30 mg/day. Rise slowly from sitting or lying positions. Syncope (fainting) can occur.

Dry mouth — Very common; stay well-hydrated and consider sugar-free gum or candy.

Headache — Common during the initial weeks of treatment, often resolves over time.

Sedation or drowsiness — Some patients experience sedation, though tranylcypromine tends to be more stimulating than phenelzine overall.

Restlessness or agitation — May occur early in treatment; tell your doctor if this is persistent.

Palpitations and tachycardia — Awareness of rapid heartbeat is reported by some patients; contact your doctor if this is persistent or distressing.

No weight gain — Unlike phenelzine, tranylcypromine is generally weight-neutral. This is considered an advantage over some other MAOIs.

Serious Side Effects: Know the Warning Signs

Tranylcypromine has two major serious risks that require immediate medical attention:

Hypertensive Crisis: The Most Dangerous Risk

Hypertensive crisis is a sudden, dangerous spike in blood pressure. It is the most serious risk associated with tranylcypromine and can be triggered by eating high-tyramine foods or taking interacting drugs.

Call 911 or go to the ER immediately if you experience:

Sudden severe headache (often described as 'the worst headache of my life')

Stiff or sore neck

Chest pain or fast heartbeat

Sweating, nausea, or vomiting

Light sensitivity or dilated pupils

Hypertensive crisis can be fatal. These are not symptoms to 'wait and see' about. High-tyramine foods to strictly avoid include aged cheeses, cured and smoked meats, fermented foods, fava beans, soy sauce, and most alcoholic beverages. Avoid these while taking tranylcypromine and for at least 2 weeks after stopping.

Serotonin Syndrome

Serotonin syndrome occurs when too much serotonin accumulates in your system — often when tranylcypromine is combined with another serotonergic drug (SSRIs, SNRIs, meperidine, dextromethorphan, St. John's Wort, MDMA, and others). This is potentially life-threatening.

Seek emergency care immediately if you experience:

Agitation, confusion, or extreme restlessness

Fast heartbeat and high temperature

Muscle twitching, rigidity, or loss of coordination

Nausea, vomiting, or diarrhea

Hallucinations

Suicidality Warning

Like all antidepressants, tranylcypromine carries a boxed warning about increased risk of suicidal thoughts or behavior in children, adolescents, and young adults (under 25). Tranylcypromine is not approved for use in pediatric patients. If you or a family member experience worsening depression, agitation, or suicidal thoughts on this medication — especially in the first few months — contact your doctor immediately or call/text 988 (Suicide & Crisis Lifeline).

Other Side Effects to Monitor

Liver enzyme elevation / hepatitis — Less common with tranylcypromine than hydrazine MAOIs, but periodic liver function monitoring may be advised.

Mania or hypomania — Risk is elevated in patients with undiagnosed or undertreated bipolar disorder. Screen carefully before initiating.

Withdrawal symptoms — If stopped abruptly: restlessness, confusion, hallucinations, diarrhea. Always taper under medical supervision.

For a full breakdown of drug interactions to avoid with tranylcypromine, see: Tranylcypromine Drug Interactions: What to Avoid and What to Tell Your Doctor.

For a general overview of the medication, see: What Is Tranylcypromine? Uses, Dosage, and What You Need to Know in 2026.