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

Nuedexta (dextromethorphan hydrobromide / quinidine sulfate) contains two active ingredients, each of which can cause its own set of side effects. Understanding what to expect — and which symptoms require prompt medical attention — helps you take Nuedexta safely and recognize when to contact your healthcare provider.

Common Side Effects of Nuedexta

The following side effects are reported most frequently by patients taking Nuedexta in clinical trials and post-marketing experience. They are generally mild to moderate and often improve as your body adjusts to the medication over the first few weeks.

Dizziness: One of the most common side effects, especially when starting treatment. Avoid driving or operating machinery until you know how Nuedexta affects you. Avoid alcohol, which can worsen dizziness.

Diarrhea: Common gastrointestinal side effect. Stay hydrated and eat smaller, easily digestible meals if diarrhea occurs.

Nausea and vomiting: May be reduced by taking Nuedexta with food, even though it can be taken with or without food.

Fatigue: Feeling tired is reported by some patients, particularly at the start of therapy.

Cough: Dextromethorphan is an antitussive (cough suppressant), but paradoxically, some patients report a mild cough while taking Nuedexta.

Peripheral edema: Swelling in the hands, feet, or ankles (water retention) has been reported.

Urinary tract infection (UTI): Reported in clinical trials, particularly in populations with neurological conditions that affect bladder function.

Falls: The combination of dizziness and the underlying neurological condition may increase fall risk. Take extra precautions with mobility and balance.

Serious Side Effects: When to Seek Immediate Medical Attention

The following side effects are uncommon but serious. Stop taking Nuedexta and seek immediate medical care if you experience any of these:

Signs of serotonin syndrome: Muscle twitching, confusion, high blood pressure, fever, restlessness, sweating, or shivering. Serotonin syndrome can be life-threatening and is most likely if Nuedexta is taken with MAOIs or serotonergic drugs. Seek emergency care immediately.

Cardiac symptoms (QT prolongation / torsades de pointes): Fainting, loss of consciousness, fast or irregular heartbeat, or severe dizziness. Nuedexta causes dose-dependent QT interval prolongation. Seek emergency care immediately.

Signs of thrombocytopenia (severely low platelets): Lightheadedness, chills, fever, nausea, and vomiting may precede or accompany dangerously low platelet levels. This is caused by quinidine's immune-mediated effects and can be severe or fatal if untreated. Stop the medication and call your doctor immediately.

Signs of liver damage (hepatotoxicity): Yellowing of the skin or eyes (jaundice), dark urine, severe fatigue, or upper right abdominal pain. Hepatitis has been reported with quinidine, particularly in the first few weeks of therapy. Discontinue immediately.

Lupus-like symptoms: Joint pain affecting multiple joints, rash, muscle aches, or fever. These can be signs of a quinidine-induced lupus-like immune reaction.

Who Is at Higher Risk for Serious Side Effects?

Certain patients are at higher risk and may require additional monitoring before and during Nuedexta therapy:

Patients with a history of prolonged QT interval, heart failure, or left ventricular dysfunction — ECG monitoring required

Patients taking SSRIs, MAOIs, or TCAs — significant drug interaction risk

Patients on digoxin — quinidine can double digoxin plasma levels

Patients with prior reactions to quinine or mefloquine — higher risk of hypersensitivity reactions

How Long Do Side Effects Last?

Most common side effects — particularly dizziness, diarrhea, and nausea — tend to improve within the first 1–2 weeks of treatment as your body adjusts. If they persist or are severe, contact your prescriber. Do not stop Nuedexta abruptly without consulting your doctor, as doing so affects your PBA symptom control.

Tips for Managing Common Nuedexta Side Effects

Dizziness: Rise slowly from sitting or lying, avoid alcohol, and don't drive until you know how the medication affects you.

Diarrhea/nausea: Stay hydrated, eat smaller meals, and consider taking Nuedexta with food.

Fatigue: Time doses so that any fatigue occurs at night when possible. Talk to your doctor if fatigue significantly impairs daily function.

For a complete guide to drug interactions, see our article on Nuedexta drug interactions. For a general overview of Nuedexta, see what is Nuedexta.