If you’ve been prescribed methadone as a treatment for opioid use disorder or severe pain, it’s important to know that, like all medication, it can cause side effects. Some may go away as your body adjusts to the medicine. Many people who take methadone have either no side effects or minor ones. Often, side effects come when you take higher doses of the drug.
If you take methadone just as your doctor prescribes, it’s unlikely that any side effects will cause you to need medical attention. But check with your doctor about how to lessen any side effects you have with this drug.
How to Manage Common Side Effects of Methadone
The two most common side effects of taking methadone are constipation and sweating. These usually go away within several weeks, once you are stable on your methadone dose. But constipation and sweating often remain.
Constipation. You may feel constipated right when you start taking methadone, or it can happen slowly. If you do not have a bowel movement for 3 days, call your doctor.
Other symptoms include bloating, straining, stomach pain, and anal bleeding.
To help prevent constipation:
- Eat more fiber like fruit, vegetables, and bran cereals.
- Drink several glasses of water or non-alcoholic liquid daily.
- Get regular exercise.
If your symptoms don’t go away, talk to your doctor about medicine such as a laxative or stool softener to help treat constipation caused by methadone.
Sweating. When you sweat heavily and it isn’t related to exercise or heat, you have hyperhidrosis. Methadone-induced hyperhidrosis is common, affecting up to 45% of people who take the drug.
If sweating is affecting your daily life, ask your doctor about prescription antiperspirants, creams, and wipes that can help. Wear natural fabrics like cotton, silk, and wool, so your skin can breathe. Keep your feet dry and wear moisture-wicking socks and shoes made of natural materials like leather, so your feet can breathe.
How to Manage Other Mild Side Effects of Methadone
Methadone may cause other mild side effects. They often improve after you have been taking the medication for a while. Tell your doctor about any side effects that don't go away or get worse, even if they’re mild. They include:
Nausea and vomiting. If you have nausea, it may help to take your methadone with food. If you vomit, try to drink small sips of water to avoid dehydration. The symptoms usually get better after a few days.
Dry mouth. This dryness will usually get better with time, as you get used to methadone. It can help to drink plenty of water or other cold drinks. Chewing sugarless gum or sucking hard candy will also add moisture to your mouth.
Drowsiness. Methadone is a depressant, and it’s common to feel sleepy and tired when you start the drug. The tiredness usually goes away within a couple of weeks as your body gets used to methadone. Don’t drive until you feel more alert and comfortable on the medicine.
Dizziness. When you first take methadone, you may feel shaky, unsteady, or lightheaded. The dizziness usually goes away within a couple of weeks as your body gets used to methadone.
Make sure that you don’t skip meals and that you drink enough water. Methadone may cause dizziness when you get up too quickly from a lying position. This is more common when you first start taking methadone. It can help to go slowly when you stand up or get out of bed. You can also rest your feet on the floor for a few minutes before standing up. Lying down for a while may also relieve dizziness.
How to Manage Less Common Side Effects of Methadone
There have been rare reports of heart rhythm and breathing problems from people taking methadone.
Respiratory depression. Also known as hypoventilation, this is extremely slow and shallow breathing. When you breathe this way, you don’t get enough oxygen, and the carbon dioxide level in your blood goes up in a condition called hypoxemia. This can make you sleepy or confused. Severe cases can be life-threatening. Many things can cause it, including obesity, COPD, and mixing methadone with other depressants. Treatment for respiratory depression depends on the cause.
For sudden symptoms, helping you to breathe better is the goal. Doctors may start bilevel positive airway pressure (BiPap or BPap) therapy, which uses a machine to push more air into your lungs. If this doesn't work, you may need to use a ventilator. You can help prevent respiratory depression by not drinking alcohol and not taking benzodiazepine medications.
Arrhythmia. This is more commonly known as an irregular heartbeat. Sometimes it causes mild symptoms like fluttering or racing, but can turn serious and even deadly. You're more likely to form an arrhythmia if you're older, a woman, or have heart disease or other heart conditions. Treatment includes medicine to keep your heart rate in check and return your heart rhythm to normal.
What to Do if You Have Serious Side Effects With Methadone
It’s rare, but methadone can cause side effects that may require medical attention right away. Some potentially serious side effects could be fatal. Fewer than 1 in 100 people have serious side effects from taking methadone. Get medical help and call your doctor if you have serious side effects. Potentially serious side effects include:
Trouble breathing. If you have shortness of breath, or your breathing becomes unusually slow, get emergency medical help and contact your doctor.
Chest pain, irregular heartbeat. A life-threatening side effect of methadone is a heart rhythm problem (arrhythmia). If you have a fast, pounding, or uneven heartbeat and feel dizzy or faint, call your doctor right away or go to the ER. Let them know if you or anyone in your family has ever had a heart rhythm problem.
Doctors may do electrocardiogram (EKG) tests to check for prolonged QT interval, a problem with the electrical system in your heart.
Allergic reaction. In rare cases, you can have a serious allergic reaction (anaphylaxis) to methadone. Symptoms may include:
- Hives
- Itching
- Peeling or blistered skin
- Tightness in your chest
- Wheezing or a hard time breathing
- Swelling of your face, lips, tongue, or throat
If you have these symptoms, call 911 or go to the ER right away.
Extreme drowsiness. Methadone is a depressant and can relax your breathing. It can cause breathing problems like sleep apnea, which is when you stop breathing briefly during sleep. If this happens, your doctor may need to lower your methadone dose. If your symptoms get worse, contact your doctor right away.
Mental health or mood changes. You may feel anxiety when you first start taking methadone. If the symptoms don’t go away after a while or get worse, your doctor may need to adjust your dose.
Taking methadone along with any medicine that affects the serotonin levels in your body puts you at greater risk. It’s crucial to talk to your doctor about any medications you take before you start taking methadone.
When methadone interacts with another medication that increases the effects of serotonin in the brain, levels of this hormone build up in the brain and reach toxic levels. This leads to a serious
central nervous system reaction called serotonin syndrome. Symptoms can start a few hours or days after taking the drugs. Or they may start later, after a dose increase. They include:
- Anxiety
- Agitation
- Fever
- Sweating
- Muscle spasms, stiffness, or twitching
- Loss of coordination
- A fast heartbeat
- Nausea, vomiting, or diarrhea
- Seeing or hearing things that are not there (hallucinations)
Adrenal gland function. Methadone may cause your adrenal glands to not work well. These glands make hormones that regulate important body functions like your metabolism, immune system function, stress response, and blood pressure, among others.
If your adrenal hormones go too low, you have adrenal insufficiency, a rare and serious condition. Your symptoms may include:
- Diarrhea
- Nausea
- Vomiting
- Loss of appetite
- Dizziness
- Fainting
- Mental depression
- Extreme tiredness or weakness
If you have these symptoms, get emergency medical help right away.
