Acetaminophen injection is used to relieve mild to moderate pain and to reduce fever. Acetaminophen injection is also used in combination with opioid (narcotic) medications to relieve moderate to severe pain. Acetaminophen is in a class of medications called analgesics (pain relievers) and antipyretics (fever reducers). It works by changing the way the body senses pain and by cooling the body.

Acetaminophen injection comes as a solution (liquid) to be injected into a vein over 15 minutes. It is usually given every 4 to 6 hours as needed to relieve pain or reduce fever.

Before receiving acetaminophen injection,

• tell your doctor and pharmacist if you are allergic to acetaminophen, any other medications, or any of the ingredients in acetaminophen injection. Ask your pharmacist or doctor for a list of ingredients.
• tell your doctor and pharmacist what prescription and nonprescription medications, vitamins, nutritional supplements, or herbal products you are taking or plan to take. Be sure to mention anticoagulants ('blood thinners') such as warfarin (Coumadin); disulfiram (Antabuse); and isoniazid (INH, Nydrazid, in Rifamate, in Rifater). Your doctor may need to change the doses of your medications or monitor you carefully for side effects. Be sure to tell your doctor if you are taking any other products that contain acetaminophen (Tylenol, found in may prescription and non prescription medications for fever, pain, and cold or flu symptoms) so that your doctor can be sure you do not receive too much acetaminophen.
• tell your doctor if you have or have ever had liver disease. Your doctor will probably tell you not to use acetaminophen injection.
• tell your doctor if you drink or have ever drunk large amounts of alcohol, if you have had severe vomiting or diarrhea or think you may be dehydrated, if you are not able to eat and drink enough to stay healthy, and if you have or have ever had kidney disease.
• tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while receiving acetaminophen injection, call your doctor.
• ask your doctor or pharmacist about the safe use of alcoholic beverages while receiving acetaminophen injection.

In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at https://www.poisonhelp.org/help. If the victim has collapsed, had a seizure, has trouble breathing, or can't be awakened, immediately call emergency services at 911.

If someone receives too much acetaminophen injection, get medical help immediately, even if the person does not have any symptoms. Symptoms of overdose may include the following:

• nausea
• vomiting
• loss of appetite
• sweating
• extreme tiredness
• lack of energy
• unusual bleeding or bruising
• pain in the upper right part of the stomach
• yellowing of the skin or eyes
• flu-like symptoms
• dark-colored urine
• coma (loss of consciousness)

Acetaminophen injection will probably be stored in the medical facility where you receive it. Talk to your doctor if you have any questions about storing your medication.

Unless your doctor tells you otherwise, continue your normal diet.

Acetaminophen injection may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

• nausea
• vomiting
• constipation
• headache
• agitation
• difficulty falling asleep and staying asleep
• pain in the place where the medication was injected

Some side effects can be serious. If you experience any of these symptoms, call your doctor immediately:

• rash
• hives
• itching
• swelling of the face, throat, tongue, lips, eyes, hands, feet, ankles, or lower legs
• hoarseness
• difficulty breathing or swallowing

Acetaminophen injection may cause other side effects. Call your doctor if you have any unusual problems while receiving this medication.

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online (http://www.fda.gov/Safety/MedWatch) or by phone (1-800-332-1088).

This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.

Before having any laboratory test, tell your doctor and the laboratory personnel that you are receiving acetaminophen injection.

Ask your pharmacist any questions you have about acetaminophen injection.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.