Zynrelef is used in adults to relieve pain for up to 72 hours after certain surgical procedures.

Zynrelef may also be used for purposes not listed in this medication guide.

Zynrelef can increase your risk of fatal heart attack or stroke. Do not use Zynrelef just before or after heart bypass surgery (coronary artery bypass graft, or CABG). This medicine may also cause stomach or intestinal bleeding, which can be fatal.

Zynrelef is administered by a healthcare professional. You will receive Zynrelef in a medical setting.

Zynrelef causes temporary loss of sensation near the surgical site.

Your breathing, blood pressure, or other vital signs will be watched closely.

You should not use Zynrelef if you are allergic to it, or if you have ever had an asthma attack or severe allergic reaction after taking aspirin or an NSAID.

Zynrelef can increase your risk of fatal heart attack or stroke, even if you don't have any risk factors. Do not use this medicine just before or after heart bypass surgery (coronary artery bypass graft, or CABG).

Zynrelef may also cause stomach or intestinal bleeding, which can be fatal. These conditions can occur without warning while you are using this medicine, especially in older adults.

Zynrelef is not used as an anesthetic in tissues around the cervix.

Tell your doctor if you have ever had:

• kidney or liver disease;

• heart disease, high blood pressure, or if you smoke;

• a heart attack, stroke, or blood clot;

• anemia (low red blood cells);

• ulcers or bleeding in your stomach;

• asthma; or

• fluid retention.

Tell your doctor if you are pregnant or plan to become pregnant. Zynrelef may harm an unborn baby if used at 20 weeks or later in pregnancy. If you are between 20 to 30 weeks of pregnancy, only use this medicine if your doctor has told you to. Avoid using this medicine if you are more than 30 weeks pregnant.

Ask a doctor if it is safe to breastfeed while using this medicine.

In a medical setting you are not likely to miss a dose.

Since Zynrelef is given in a medical setting, you will be watched closely to make sure you do not receive too much of Zynrelef. Your healthcare provider will quickly treat you if you have overdose symptoms.

Avoid drinking alcohol. Heavy drinking can increase your risk of stomach bleeding.

Avoid taking aspirin while you are using Zynrelef, unless your doctor tells you to.

Ask a doctor or pharmacist before using other medicines for pain, fever, swelling, or cold/flu symptoms. They may contain ingredients similar to Zynrelef (such as aspirin, ibuprofen, ketoprofen, or naproxen).

Get emergency medical help if you have signs of an allergic reaction (hives, difficult breathing, swelling in your face or throat) or a severe skin reaction (fever, sore throat, burning eyes, skin pain, red or purple skin rash with blistering and peeling).

Seek medical treatment if you have a serious drug reaction that can affect many parts of your body. Symptoms may include skin rash, fever, swollen glands, muscle aches, severe weakness, unusual bruising, or yellowing of your skin or eyes.

Zynrelef may cause serious side effects. Call your doctor at once if you have:

• low red blood cells (anemia)--pale skin, tiredness, feeling light-headed or short of breath, cold hands and feet;

• liver problems--loss of appetite, stomach pain (upper right side), tiredness, itching, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes);

• stomach bleeding--bloody or tarry stools, coughing up blood or vomit that looks like coffee grounds;

• chest pain, shortness of breath, weakness, or slurring of speech; or

• pale, gray, or blue colored skin, headache, rapid heart rate, shortness of breath, lightheadedness, or tiredness.

Common side effects of Zynrelef may include:

• constipation, vomiting; or

• headache.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Tell your doctor about all your other medicines, especially:

• a blood thinner--warfarin, Coumadin, Jantoven;

• an antidepressant;

• heart or blood pressure medication, including a diuretic or "water pill";

• lithium;

• methotrexate;

• cyclosporine; or

• pemetrexed.

This list is not complete and many other drugs may affect Zynrelef. This includes prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.