Quillivant XR Side Effects: What You Need to Know

Quillivant XR (Methylphenidate extended-release oral suspension) is a liquid stimulant medication used to treat ADHD in patients aged 6 and older. Like all stimulant medications, it comes with side effects — some mild and manageable, others that need immediate medical attention.

This guide covers what the FDA labeling actually says, what real patients experience, and when you should call your doctor.

What Is Quillivant XR?

Quillivant XR is a long-acting liquid form of Methylphenidate, manufactured by Tris Pharma. It belongs to the CNS stimulant drug class and is classified as a Schedule II controlled substance. Unlike most ADHD medications that come as tablets or capsules, Quillivant XR is an oral suspension — making it a key option for patients who can't swallow pills. For a deeper dive, see our full guide on what Quillivant XR is and how it works.

Common Side Effects

These side effects are the most frequently reported in clinical trials. They're usually mild to moderate and often improve within the first few weeks of treatment:

• Decreased appetite — This is the most common side effect of Quillivant XR and most stimulant medications. Many parents notice their child eats less during the day when the medication is active.
• Trouble sleeping (insomnia) — Difficulty falling asleep is common, especially if the medication is taken too late in the day. Quillivant XR should be taken in the morning.
• Nausea and vomiting — Stomach upset can occur, particularly when starting the medication or increasing the dose.
• Stomach pain and indigestion — GI discomfort is reported by some patients, often improving with food.
• Weight loss — Related to decreased appetite. Your doctor should monitor weight regularly, especially in children.
• Anxiety — Some patients experience new or worsened anxiety on stimulant medications.
• Dizziness — Usually mild and often resolves as the body adjusts to the medication.
• Irritability and mood swings — Can occur as the medication wears off (sometimes called the "rebound effect") or throughout the day.
• Fast heartbeat and increased blood pressure — Stimulants can raise heart rate and blood pressure. Your doctor should monitor these at each visit.

Serious Side Effects

These are less common but require immediate medical attention. Contact your doctor right away — or call 911 — if you experience any of the following:

• Heart problems — Quillivant XR carries a risk of sudden death in patients with pre-existing heart defects or serious heart problems. In adults, stroke and heart attack have been reported. Seek emergency care for chest pain, shortness of breath, or fainting.
• New or worsening psychiatric symptoms — This includes hallucinations (seeing or hearing things that aren't real), paranoia, mania, or psychosis. These can occur even in patients with no prior psychiatric history.
• Peripheral vasculopathy (Raynaud's phenomenon) — Fingers or toes that feel numb, cool, painful, or change color (pale, blue, or red). This indicates a circulation problem.
• Priapism — A prolonged, painful erection lasting more than 4 hours. This is a medical emergency that requires immediate treatment.
• Seizures — Quillivant XR may lower the seizure threshold. Patients with a history of seizures should be monitored closely.
• Growth suppression in children — Long-term use of stimulants can slow growth. Doctors should track height and weight over time and consider medication breaks if growth is affected.
• Increased eye pressure (glaucoma) — Report any changes in vision or eye pain to your doctor.

Boxed Warning: Abuse and Addiction

Quillivant XR carries a boxed warning (the FDA's most serious warning) about the risk of abuse, misuse, and addiction. As a Schedule II stimulant, it has high abuse potential. Your doctor should assess your risk before prescribing and monitor you during treatment. Never take more than prescribed, and store the medication securely.

Side Effects in Specific Populations

Children Under 6

Quillivant XR is not recommended for children under 6 years old. Studies showed higher plasma drug levels and increased side effects in this age group.

Pregnant or Breastfeeding

Quillivant XR is Pregnancy Category C — meaning it's not known whether it causes harm to an unborn baby. It does pass into breast milk. If you're pregnant, planning to become pregnant, or breastfeeding, talk to your doctor about the risks and benefits before taking this medication.

Patients with Heart Conditions

People with pre-existing heart defects, cardiomyopathy, heart rhythm problems, or other serious cardiac conditions face a higher risk of serious cardiovascular events on stimulant medications. A thorough cardiac evaluation is recommended before starting Quillivant XR.

Patients with Psychiatric History

Those with a history of psychosis, bipolar disorder, or depression may experience worsening symptoms. New psychiatric symptoms can also emerge in patients without prior history.

How to Manage Common Side Effects

Most mild side effects can be managed with simple strategies:

• For decreased appetite: Serve a good breakfast before the medication kicks in. Offer calorie-dense snacks in the evening when appetite returns. Don't force meals during the day.
• For insomnia: Make sure the dose is taken first thing in the morning. Establish a consistent bedtime routine. Avoid screens before bed. Talk to your doctor about dose adjustment if sleep problems persist.
• For stomach upset: Take with food if nausea is an issue. Small, frequent meals may help.
• For mood swings and irritability: Track when symptoms occur. If they happen as the medication wears off, your doctor may adjust the dose or timing.
• For increased heart rate or blood pressure: Your doctor should check vitals at every visit. Limit caffeine intake, which can worsen these effects.

If side effects don't improve after 2-4 weeks, or if they're significantly affecting quality of life, talk to your doctor. Dose adjustments often help. In some cases, switching to a different ADHD medication may be the best approach — see our guide on alternatives to Quillivant XR.

When to Call Your Doctor

Call your doctor if you notice:

• Side effects that don't go away or get worse over time
• Significant weight loss or growth changes in a child
• New anxiety, agitation, or mood changes
• Signs of circulation problems in fingers or toes

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

• Chest pain, shortness of breath, or fainting
• Hallucinations or psychotic symptoms
• Seizures
• A prolonged, painful erection
• Signs of a severe allergic reaction (rash, swelling, difficulty breathing)

Final Thoughts

Most people who take Quillivant XR experience mild side effects that improve with time. The most common issues — decreased appetite, trouble sleeping, and stomach upset — are manageable with the right strategies. Serious side effects are rare but important to know about.

The key is staying in close contact with your doctor, especially during the first few months of treatment. Regular check-ins allow for dose adjustments and early detection of any problems.

If you're having trouble finding Quillivant XR at your pharmacy, Medfinder can help you check which pharmacies have it in stock near you.