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

What You Need to Know About Perphenazine Side Effects

Perphenazine is a first-generation antipsychotic that has been used for decades to treat schizophrenia and severe nausea. Like all antipsychotic medications, it comes with a range of potential side effects — some mild and manageable, others serious enough to require immediate medical attention.

This guide breaks down the most common and serious side effects of Perphenazine, which populations are at higher risk, and when you should contact your doctor.

What Is Perphenazine?

Perphenazine (formerly sold under the brand name Trilafon) is a phenothiazine-class antipsychotic that works by blocking dopamine receptors in the brain. It's FDA-approved for schizophrenia and severe nausea and vomiting. For a complete overview, see our guide on what Perphenazine is and how it's used.

Common Side Effects

Most people who take Perphenazine experience at least some side effects, especially when starting the medication or after a dose increase. These are generally mild and often improve over time:

• Drowsiness — One of the most frequently reported side effects. It's often worse during the first few weeks of treatment.
• Dizziness — Can occur when standing up quickly (orthostatic hypotension). Rise slowly from sitting or lying positions.
• Blurred vision — Related to Perphenazine's anticholinergic effects. Usually temporary.
• Constipation — Drink plenty of water, eat fiber-rich foods, and stay active to help manage this.
• Dry mouth — Sip water throughout the day or use sugar-free gum or lozenges.
• Nasal congestion — May feel like a stuffy nose without being sick.
• Weight gain — Monitor your weight and discuss dietary strategies with your doctor.
• Restlessness (akathisia) — A feeling of needing to keep moving. This can be very uncomfortable and should be reported to your doctor.

Serious Side Effects

While less common, Perphenazine can cause serious side effects that require prompt medical attention. Contact your doctor or go to the emergency room if you experience any of the following:

Tardive Dyskinesia

This is a movement disorder that causes involuntary, repetitive movements — often of the face, tongue, and jaw. Tardive dyskinesia can develop after months or years of taking Perphenazine and may be irreversible in some cases. The risk increases with longer use and higher doses. Report any unusual movements to your doctor immediately.

Neuroleptic Malignant Syndrome (NMS)

NMS is a rare but life-threatening reaction to antipsychotic medications. Symptoms include:

• High fever (above 104°F)
• Severe muscle rigidity
• Altered mental status (confusion, delirium)
• Rapid heart rate
• Unstable blood pressure

NMS is a medical emergency. If you or someone you know develops these symptoms while taking Perphenazine, call 911 immediately.

Extrapyramidal Symptoms (EPS)

EPS are movement-related side effects that include:

• Dystonia — Sudden, painful muscle contractions (often in the neck, jaw, or eyes)
• Parkinsonism — Tremor, stiffness, slow movements, shuffling gait
• Akathisia — Intense inner restlessness and urge to move

EPS are more common with first-generation antipsychotics like Perphenazine. Your doctor may prescribe medications like Benztropine or Diphenhydramine to manage these symptoms.

Other Serious Side Effects

• Orthostatic hypotension — Significant drop in blood pressure when standing, which can cause fainting
• Seizures — Perphenazine can lower the seizure threshold
• Agranulocytosis — A dangerous drop in white blood cells that increases infection risk. Seek care if you develop unexplained fever, sore throat, or mouth sores.
• Jaundice/liver damage — Yellowing of the skin or eyes, dark urine, or abdominal pain should be reported immediately
• Prolonged QT interval — Can lead to dangerous heart rhythms. Your doctor may monitor with periodic EKGs.

Specific Populations at Higher Risk

Elderly Patients

Perphenazine carries a boxed warning about increased mortality in elderly patients with dementia-related psychosis. It is not approved for this use. Elderly patients are also more susceptible to orthostatic hypotension, falls, and tardive dyskinesia.

Pregnant and Breastfeeding Women

Perphenazine should only be used during pregnancy if the benefits clearly outweigh the risks. It is excreted in breast milk, so discuss breastfeeding plans with your doctor.

Patients with Cardiovascular Disease

The QT-prolonging effects and blood pressure changes associated with Perphenazine require careful monitoring in patients with heart conditions.

Patients with Liver Impairment

Perphenazine is metabolized by the liver. Patients with liver disease may need lower doses and more frequent monitoring.

How to Manage Side Effects

Many Perphenazine side effects can be managed with simple strategies:

• Take it at bedtime — If drowsiness is a problem, ask your doctor about taking your dose at night.
• Stay hydrated — Helps with dry mouth and constipation.
• Rise slowly — Reduces dizziness from orthostatic hypotension.
• Monitor your weight — Track changes and adjust diet and exercise as needed.
• Don't stop suddenly — Abruptly discontinuing Perphenazine can cause withdrawal symptoms including nausea, vomiting, dizziness, and tremors. Always taper under your doctor's supervision.
• Keep all follow-up appointments — Regular check-ins allow your doctor to catch problems early and adjust your dose.

For information on drug interactions that may worsen side effects, see our dedicated guide.

Final Thoughts

Perphenazine is an effective medication for many people, but understanding its side effects helps you use it safely. Most common side effects are manageable, and serious ones are rare — but knowing the warning signs can be lifesaving.

Talk to your doctor if any side effects are bothering you. There may be ways to adjust your dose, switch the timing, or add medications to help. And if you need help finding Perphenazine at an affordable price, Medfinder can help you locate it in stock near you.