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Fluids & Electrolytes
Approved by the FDA in 2010, the I.V. form of acetaminophen (ofirmev injection) is indicated to manage mild-to-moderate pain or moderate-to-severe pain with an adjunctive opioid. It can also be used to reduce fever. Let's take a closer look.
Administering acetaminophen I.V. rather than orally may be indicated for patients who are:
* experiencing nausea, vomiting, or diarrhea
* critically ill
* experiencing a decreased level of consciousness
* receiving numerous medications by mouth
* being treated with medications known to cause nausea and vomiting, such as chemotherapy agents.
It's contraindicated for patients with known hypersensitivity to acetaminophen or any components of the I.V. formulation, and in patients with severe hepatic impairment or severe active liver disease. For more information, see Contraindications, warnings, and precautions.
I.V. acetaminophen is currently approved only for patients age 2 and older. The Pediatric Equity Research Act of 2003 requires controlled clinical trials on drugs intended for pediatric patients. The drug's manufacturer is currently conducting research to evaluate the safety and effectiveness of administering acetaminophen via the I.V. route in children under age 2.
Patients taking certain medications may experience a drug-drug interaction when two or more specific medications are mixed or taken within a short period of time. Drug-drug interactions can cause signs and symptoms ranging from minor itching or a rash to serious, potentially life-threatening complications such as breathing difficulties, predisposition to hemorrhage, and cardiac dysrhythmias.
Patients taking oral anticoagulants such as warfarin concurrently with oral acetaminophen are at increased risk for bleeding. Although research on ofirmev is limited, patients taking anticoagulants should be monitored for signs of bleeding, such as hematuria, melena, bleeding gums, and nose bleeds, when being given I.V. acetaminophen. In addition, monitor serum lab values closely, watching specifically for low partial thromboplastin time or high international normalized ratio values.
Drugs that alter the metabolism of acetaminophen, such as isoniazid, can increase the risk of hepatotoxicity. Even after isoniazid is discontinued, it will continue to delay clearance of acetaminophen from the body. Patients receiving isoniazid shouldn't take ofirmev to avoid potential life threatening drug-drug interactions.
Patients who consume three or more alcoholic drinks daily or who binge drink are also at risk for hepatotoxicity when taking acetaminophen. Teach patients that acetaminophen and alcohol don't mix.
Patients taking the nonsteroidal anti-inflammatory drug dolobid may experience a 50% increase in serum acetaminophen levels when taking the drug with acetaminophen. This can result in accidental acetaminophen overdose.
Remember, because acetaminophen potentially interacts with many drugs, never infuse it with any other medication.
I.V. acetaminophen is provided in a single-use, vacuum-sealed glass vial containing 1,000 mg of acetaminophen in 100 mL of fluid (10 mg/mL). The fluid in the vial should be clear. If the fluid is discolored or you see particles floating in it, consider it contaminated. Never administer the drug if you have any doubts; return it to the pharmacy according to your facility's policy and procedure.
Before beginning the infusion, check to see if the patient is taking oral acetaminophen or any combination product that contains acetaminophen and make sure not to exceed the maximum daily dose of acetaminophen by any route. Excessive acetaminophen dosages are toxic to the liver. For most adults, the maximum total daily dose is 4,000 mg.
Ofirmev injection can be given as a single treatment or in repeated doses. Administer the drug as directed in the product insert as a primary infusion through vented I.V. tubing. Don't combine it with any other drug or run a secondary infusion on the same line.
The recommended dosage for adults weighing more than 50 kg (110 lb) is 1,000 mg every 6 hours or 650 mg every 4 hours to a maximum of 4,000 mg/day. For children, adolescents, and adults weighing less than 50 kg, the recommended dosage is 15 mg/kg every 6 hours or 12.5 mg/kg every 4 hours to a maximum of 75 mg/kg/day. Dosage intervals should be at least 4 hours for all patients. Administer the infusion over 15 minutes (set the infusion pump at 400 mL/hr). Discard the I.V. tubing following each infusion.
Monitor the patient for adverse reactions and assess response to treatment. Expect a reduction in fever and pain within 15 minutes of initiating the infusion.
In clinical trials, chills were the most common adverse reaction to the drug, occurring in 26% of all adults and 5% of all children. Besides chills, adult patients may experience insomnia, headache, nausea, and vomiting. In addition to these reactions, pediatric patients may experience agitation, itching, shortness of breath, and constipation. Report adverse reactions promptly and intervene as indicated.
What if the prescribed dosage is a fraction of the volume in the drug vial? Both the milliliters and milligrams should be verified to ensure that the proper dose is drawn up and administered. Make sure that if a volume of drug is removed from the vial, the medication is properly labeled by two licensed nurses or a pharmacist to ensure that the dosage and volume are correct. Similarly, prescribers should specify both milligrams and milliliters to be administered when writing an order. The solution shouldn't be diluted before administration, which would increase the likelihood of under-dosing.
A common reason for overdose is the failure to reduce the dosage for patients weighing less than 50 kg. An overdose may also occur when the maximum daily dose is inadvertently exceeded because the patient was also taking an oral form of acetaminophen. Nurses should be aware that the antidote for acetaminophen overdose is oral N-acetylcysteine.
When caring for a patient receiving ofirmev, keep these important points in mind.
* Monitor the patient for hypersensitivity and allergic reactions during the infusion and for at least 30 minutes afterward.
* Monitor renal function. For patients with a creatinine clearance of less than 30 mL/min, the prescriber may need to discontinue the infusion, reduce the dosage, or increase the dosage interval.
* Routinely monitor serum acetaminophen levels for patients receiving frequent or large doses of any form of acetaminophen to avoid toxicity.
* If slow coagulation occurs, vitamin K may also be administered.
* Monitor liver enzymes to assess for signs of liver damage.
As pharmaceutical research continues to improve the lives of our patients, we must stay well-informed about recently approved medications. Ofirmev offers the same therapeutic benefit as oral acetaminophen without the gastrointestinal discomfort. Share your newly acquired knowledge about ofirmev with your healthcare team members so that your patient population can benefit from this medication.
The same basic precautions and guidelines apply to I.V. acetaminophen as for the oral formulation. It's contraindicated for patients who:
* are hypersensitive to acetaminophen or any components in the I.V. formulation
* have severe hepatic impairment or severe active liver disease, such as hepatitis or cirrhosis
* are younger than age 2.
Use ofirmev with caution in patients with renal impairment; adjust the dosage or lengthen dosage intervals as prescribed. Also use caution in patients who have a history of alcohol abuse, severe hypovolemia, or chronic malnutrition. Closely monitor postsurgical patients receiving I.V. acetaminophen because it can mask a fever.
Although ofirmev isn't contraindicated in pregnancy, it's categorized as Pregnancy Class C by the FDA. Pregnancy Class C drugs could potentially harm the fetus and need further study to comprehensively evaluate fetal safety. I.V. acetaminophen may be prescribed to a pregnant woman if the potential benefits outweigh the risks.
Many drugs have the potential to interact with I.V. acetaminophen. For example, it's generally not recommended for patients receiving antiepileptics because of the increased risk of hepatotoxicity. Other medications that may cause drug-drug interactions with ofirmev include:
* cyanide antidote kit (amyl nitrite/sodium nitrite/sodium thiosulfate).
Consult with the pharmacist or prescriber if you have any questions about a potential drug-drug interaction.
Source: http://Drugs.com. Ofirmev. http://www.drugs.com/pro/ofirmev.html.
Beringer RM, Thompson JP, Parry S, Stoddart PA. Intravenous paracetamol overdose: two case reports and a change to national treatment guidelines. Arch Dis Child. 2011;96(3):307-308.
http://Drugs.com. FDA approves ofirmev. http://www.drugs.com/newdrugs/cadence-pharmaceuticals-announces-fda-approval-ofi.
http://Drugs.com. Ofirmev. http://www.drugs.com/pro/ofirmev.html.
FDA. Pediatric postmarket adverse event review. http://www.fda.gov/downloads/AdvisoryCommittees/CommitteesMeetingMaterials/Pedia.
Wininger SJ, Miller H, Minkowitz HS, et al. A randomized, double-blind, placebo-controlled, multicenter, repeat-dose study of two intravenous acetaminophen dosing regimens for the treatment of pain after abdominal laparoscopic surgery. Clin Ther. 2010;32(14):2348-2369.
Zhang Q, Bal-dit-Sollier C, Drouet L, et al. Interaction between acetaminophen and warfarin in adults receiving long-term oral anticoagulants: a randomized controlled trial. Eur J Clin Pharmacol. 2011;67(3):309-314.
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