Methadone and Buprenorphine Side Effects in Opioid Use Disorder Treatment
Jan, 20 2026
What You Need to Know About Methadone and Buprenorphine Side Effects
If you're considering medication for opioid use disorder (OUD), you're not alone. Over 1.6 million people in the U.S. are currently in treatment with methadone or buprenorphine. These drugs save lives-reducing cravings, stopping withdrawal, and cutting overdose deaths by up to 50%. But they also come with side effects that can make daily life harder. Some people feel like a zombie. Others can't sleep, can't have sex, or can't stop constipation. And for some, the medication just doesn't work well enough.
The truth is, methadone and buprenorphine aren't the same. One is stronger but riskier. The other is safer but sometimes not strong enough. Choosing between them isn't about which is better overall-it's about which fits your body, your history, and your life.
Methadone: Effective but Risky
Methadone has been used since the 1940s to treat opioid addiction. It works by fully activating opioid receptors in the brain, which stops cravings and withdrawal. But because it's a full agonist, it doesn't stop there. At higher doses, it can slow your breathing dangerously-especially in the first few weeks of treatment.
Studies show that methadone causes more serious side effects than buprenorphine. About 5-15% of people on methadone develop QTc prolongation-a heart rhythm problem that can lead to sudden cardiac arrest. That risk jumps to 25-35% if you're taking more than 100mg a day. That's why doctors usually require an EKG before starting and again after a few weeks.
Constipation is another major issue. Nearly 40% of people on methadone say they need laxatives every day. Nausea and drowsiness are common too-around 20-30% of users report feeling too sleepy to drive or work. One Reddit user described it as, "I stopped using heroin, but now I feel like I'm walking through molasses."
Sexual side effects are often ignored but very real. Around 30% of long-term methadone users experience low libido, erectile dysfunction, or loss of orgasm. This isn't just a personal problem-it can make people feel ashamed and stop treatment.
Seizures are rare but possible, especially if you have a history of epilepsy or take other medications that lower the seizure threshold. And if you drink alcohol or take benzodiazepines like Xanax or Valium while on methadone, your risk of fatal overdose goes up 300-400%.
Buprenorphine: Safer, But With Its Own Problems
Buprenorphine is a partial agonist. That means it activates opioid receptors, but only up to a point. This "ceiling effect" makes it much safer. Even at high doses, it doesn't suppress breathing the way methadone does. That’s why it can be prescribed in a doctor’s office instead of a special clinic.
But safety comes with trade-offs. The most common side effect? Headaches. Around 30-40% of people on buprenorphine (especially Suboxone) report them. Then there’s the mouth stuff. Because it’s placed under the tongue, many users get numbness, soreness, or a weird taste. About 25-35% say their mouth feels irritated or painful after taking it.
But the biggest complaint? It doesn’t work well enough. Up to 73% of people on buprenorphine say they still have breakthrough cravings-especially if they’ve been using high doses of opioids for years. That’s because buprenorphine’s ceiling effect caps its strength. If your tolerance is high, 16mg or even 24mg might not be enough to fully block cravings. Some people end up using again-not because they want to, but because the medication isn’t strong enough.
One patient on Healthgrades wrote: "I take Suboxone and I’m not using heroin, but I still think about it every day. I can’t focus at work. I feel like I’m half-treated."
Unlike methadone, buprenorphine rarely causes heart rhythm problems. It also doesn’t cause sexual dysfunction as often. But it can still cause dizziness, nausea, and constipation-just less frequently.
How the Two Compare: Side Effects at a Glance
| Side Effect | Methadone | Buprenorphine |
|---|---|---|
| Drowsiness | 18-28% | 12-20% |
| Constipation | 25-40% | 20-30% |
| Nausea/Vomiting | 20-35% | 15-25% |
| Headaches | 8-15% | 30-40% |
| Mouth/Numbness Issues | Rare | 25-35% |
| QTc Prolongation (Heart Risk) | 5-35% (dose-dependent) | Less than 1% |
| Sexual Dysfunction | ~30% | 5-10% |
| Breakthrough Cravings | 15-20% | 40-70% |
| Overdose Risk (alone) | High | Low |
These numbers aren’t just statistics. They reflect real choices. If you’re someone who works a job that requires alertness, buprenorphine might let you keep working. If you’ve been using high doses of fentanyl for years, methadone might be the only thing that keeps you from relapsing.
Who Benefits Most From Each Medication?
There’s no one-size-fits-all answer. But experts agree on some patterns.
Methadone works best for:
- People with long-term, high-dose opioid use (especially fentanyl)
- Those who’ve tried buprenorphine and still had cravings
- Patients who need the strongest possible craving control
- People with stable housing and access to daily clinic visits
Buprenorphine works best for:
- People new to treatment or with lower opioid tolerance
- Those who can’t access daily methadone clinics
- People with heart conditions or a history of overdose
- Those who want to avoid daily clinic visits
But here’s the catch: even if buprenorphine is safer, it doesn’t work for everyone. About 30-40% of people who start on buprenorphine eventually switch to methadone because it’s not strong enough. That’s not failure-it’s just biology.
What You Can Do About Side Effects
Side effects don’t have to be permanent. Many fade after a few weeks as your body adjusts. But some need active management.
For constipation: Drink more water. Eat fiber. Use stool softeners like docusate. Avoid stimulant laxatives long-term. Some people need daily Miralax.
For drowsiness: Don’t drive or operate heavy machinery until you know how the medication affects you. If you’re still tired after 3-4 weeks, talk to your doctor about adjusting your dose.
For mouth irritation (buprenorphine): Let the tablet dissolve completely under your tongue. Don’t swallow it. Don’t eat or drink for 15 minutes after. If it hurts, ask about switching to a film (like Zubsolv) or a monthly injection (Sublocade).
For heart concerns (methadone): Get a baseline EKG before starting. Repeat it after 1-2 weeks and then every 6-12 months if you’re on high doses.
For sexual side effects: Talk to your provider. Sometimes switching medications helps. Sometimes adding a low-dose antidepressant (like bupropion) can improve libido without triggering relapse.
When to Call Your Doctor
Not all side effects are normal. Call your provider immediately if you experience:
- Slow or shallow breathing
- Chest pain or irregular heartbeat
- Fainting or dizziness that won’t go away
- Seizures
- Severe swelling of the face, lips, or throat
These are rare-but life-threatening. Don’t wait.
What’s Changing in 2026
Things are improving. New long-acting forms of buprenorphine-like monthly injections and six-month implants-are reducing daily side effects like nausea and mouth irritation. Methadone formulations with lower heart risk are in clinical trials.
Doctors are also getting better at screening. More clinics now offer EKGs, and naloxone is being co-prescribed more often. But access is still uneven. Many primary care providers still don’t know how to properly start someone on buprenorphine, leading to painful withdrawal or ineffective doses.
The biggest shift? The focus is moving from "which drug is better?" to "which drug is right for you?"
Final Thoughts: It’s Not About Perfection
Neither methadone nor buprenorphine is perfect. Both have side effects. Both can be hard to live with. But they’re also the most effective tools we have to keep people alive and in recovery.
If you’re struggling with side effects, you’re not weak. You’re human. And you’re not alone. Many people switch between the two. Many go back and forth. That’s not failure-it’s part of finding what works.
The goal isn’t to feel perfectly normal. It’s to feel stable enough to rebuild your life. To hold a job. To be a parent. To stop fearing overdose. That’s possible-with the right medication, the right support, and the right expectations.
Can you overdose on methadone or buprenorphine?
Yes, but the risk is very different. Methadone can cause fatal overdose, especially during the first two weeks of treatment or if mixed with alcohol or benzodiazepines. Buprenorphine has a ceiling effect that limits respiratory depression, making overdose much less likely-even at high doses. But combining it with other depressants still raises the risk significantly.
Which medication is better for long-term use?
Methadone has higher retention rates-about 81% of people stay in treatment after two years compared to just 11% for buprenorphine. But that doesn’t mean buprenorphine is worse. Many people leave buprenorphine treatment because they feel it’s not strong enough, not because they relapse. For long-term stability, methadone often wins. For safety and convenience, buprenorphine is preferred.
Do these medications cause weight gain?
Not directly. But many people gain weight after starting treatment because their metabolism returns to normal, cravings for food increase, and they’re no longer using opioids that suppress appetite. Weight gain is more common with methadone due to its stronger effect on appetite regulation and sedation, which reduces physical activity.
Can you switch from methadone to buprenorphine?
Yes, but it’s tricky. You must be on a low methadone dose (usually 30mg or less) and fully detoxed from opioids for 24-48 hours before starting buprenorphine. If you start too soon, you’ll get sudden, severe withdrawal called precipitated withdrawal. This is painful and dangerous. Always do this under medical supervision.
Why do some people say buprenorphine doesn’t work for them?
Because of the ceiling effect. If you’ve been using high doses of opioids for years-especially fentanyl-your body may need more opioid activation than buprenorphine can provide. At doses above 16-24mg, it doesn’t get stronger. So if your tolerance is high, you might still have cravings or even use again. That’s not a personal failure-it’s a pharmacological limit.
Is it safe to take methadone or buprenorphine while pregnant?
Yes. Both are recommended during pregnancy. Stopping opioids suddenly can cause miscarriage or preterm labor. Methadone has been used for decades in pregnant women and is considered the gold standard. Buprenorphine is also safe and may cause less severe neonatal abstinence syndrome (NAS) in newborns. Always work with a provider experienced in addiction and pregnancy care.
Can you drive while on methadone or buprenorphine?
It depends. In the first few weeks, both can cause drowsiness and slow reaction times. Many people can’t drive safely during induction. After stabilization, most people can drive without issue. Methadone users are more likely to report driving difficulties due to sedation. Always test your reaction time and never drive if you feel foggy or sleepy.
How long do side effects last?
Most mild side effects-like nausea, dizziness, or headaches-fade within 1-4 weeks as your body adjusts. Constipation and sexual side effects often persist longer and may require ongoing management. If side effects are still severe after 6-8 weeks, talk to your provider. Your dose may need adjustment, or you may need to switch medications.
Next Steps: What to Do Now
If you’re on one of these medications and struggling with side effects, don’t suffer in silence. Talk to your provider. Ask about dose changes. Ask about switching. Ask about support resources.
If you’re not in treatment yet, know this: you don’t have to choose between being addicted and being medicated. Medication-assisted treatment is the most effective way to recover. Side effects are real-but they’re manageable. And they’re far better than the alternative.
The goal isn’t to feel perfect. It’s to feel stable enough to live again.