Isentress: Side Effects, Dosage, Information

Written by Rachel Nall, RN, BSN | Published on October 3, 2014
Medically Reviewed by Susan J. Bliss, RPh, MBA on October 3, 2014

What Is Isentress?

Brand Name: Isentress
Generic Name: Raltegravir

Isentress (pronounced eye-sen-tris) is a chewable or film-coated tablet used to treat HIV. Doctors prescribe Isentress along with other HIV medications, especially Truvada. The U.S. Food and Drug Administration has approved Isentress for adults and for children who are least two years old and weigh at least 10 kilograms (approximately 22 pounds).

Read the FDA description of Isentress.

What Does Isentress Do?

Isentress is not a cure for HIV. It is an integrase inhibitor, which helps reduce the amount of HIV viruses in your body by blocking an enzyme that builds or integrates the virus into CD4+ T cells. This effect can improve your immune system, making you less susceptible to harmful infections.

What Are the Typical Doses?

The dosage of Isentress for adults and children who weigh at least 25 kilograms (55 pounds) is one 400 milligrams (mg) tablet twice a day. If the patient is not able to swallow tablets, there is a chewable tablet with different dosing. The solid tablet and chewable tablets are not interchangeable. Isentress may be taken with or without food. For children who are at least 4 weeks old and who weigh at least 3 kilograms (6.6 pounds) and less than 25 kilograms (55 pounds), Isentress is dosed by weight and is given in oral suspension or chewable tablet form, as determined by the physician.

This information is a summary. Before starting this medication, discuss questions with your healthcare provider and make sure you understand dosage instructions.

What Should I Tell My Doctor Before Starting Isentress?

Tell your doctor before taking Isentress if you:

  • are breastfeeding or planning on breastfeeding, as the medication and HIV virus can be transmitted to the baby
  • have liver problems, such as hepatitis B or C
  • have phenylketonuria, as Isentress tablets contain aspartame
  • are pregnant or are planning on becoming pregnant
  • have been diagnosed with a muscle disorder such as rhabdomyolysis

What Medications May Interact with Isentress?

Always tell your physician about any prescription medications or herbal remedies you are taking.

Antacids and minerals like calcium, aluminum hydroxide, magnesium and iron, if taken with Isentress, have been found to reduce its absorption. Taking vitamins and antacids containing these minerals four hours apart from Isentress minimized the risk of this interaction. 

When Isentress is taken with rifampin, also known as Rifadin, Rifamate, Rifater, or Rimactane, the levels of Isentress drop. This is because rifampin stimulates the metabolism of both drugs.  Rifampin is prescribed to treat tuberculosis. Physicians may manage patients on both drugs by adjusting the dose of Isentress. Other drugs including phenytoin and phenobarbital, given to prevent seizures, may also have this effect and physicians may need to manage dosing accordingly.

Other antiretroviral drugs may interact with Isentress (atazanavir or Reyataz and tenofovir or Viread) but the effects are small and physicians are aware of them. 

Drugs that are used to reduce cholesterol and triglycerides (statins and fibric acids), already have the risk of causing muscle aching that if ignored, can lead to rhamdomyolysis.  When Isentress is added to these drugs, the risk increases.  Doctors may manage patients on both drugs, or discontinue the statin or fibric acid. Zidovudine (Retrovir) also has this risk.  These drugs include:

  • fenofibrate (Tricor)
  • gemfibrozil (Lopid)
  • statins (HMG-CoA reductase inhibitors, such as Lipitor, Zocor, and Mevacor)
  • zidovudine (Retrovir)

Possible Side Effects of Isentress

Possible Adverse and Emergency Side Effects

Isentress has a smaller risk of side effects than many drugs for HIV.  There are some severe and emergent side effects of these medications. Contact your medical provider immediately if you experience:

  • immune system changes that make you feel like you have a viral infection immediately after taking the medication
  • a severe allergic reaction, including swelling in your mouth or face, difficulty breathing, extreme tiredness, joint aches, fever, and generally feeling ill
  • a severe skin reaction that causes blisters or sores in your mouth, peeling skin, or redness or swelling in your eyes
  • changes in liver function, which may include symptoms of liver disease, such as yellowing of the skin or whites of the eyes, darkened urine, nausea, vomiting, appetite loss, pale-colored stool, and aching and tenderness just below your ribs on your right side. The risk is higher in patients who also have hepatitis B and/or hepatitis C infection. 

About 10 percent of patients may have a substantial increase in blood sugar while taking Isentress.

Possible Nonemergency Side Effects

The following side effects may occur but do not usually represent an emergency. Discuss them with your doctor or healthcare professional if they continue or are bothersome.

These side effects occurred in more than 2 percent of patients studied:

  • difficulty sleeping
  • dizziness
  • headache
  • nausea
  • tiredness

These side effects occurred rarely (in less than 2 percent of patients studied):

  • allergic reaction
  • depression (this is more likely if patients have history of depression)
  • genital herpes
  • herpes zoster, including shingles
  • kidney failure
  • kidney stones
  • stomach upset
  • suicidal thoughts
  • vomiting
  • weakness

This list may not describe all possible side effects. Call your doctor or healthcare provider for advice about side effects. You can report side effects to the FDA at 1-800-FDA-1088.

Where Should I Keep Isentress?

Both Isentress film-coated tablets and chewable tablets should be stored at room temperature or between 68 and 77 degrees Fahrenheit (20 to 25 degrees Celsius). The drug may be occasionally stored between 59 and 86 degrees Fahrenheit (15 to 30 degrees Celsius).

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Important FDA Warnings

FDA WARNING: SEVERE, POTENTIALLY LIFE-THREATENING AND FATAL SKIN REACTIONS HAVE BEEN REPORTED. THIS INCLUDES CASES OF STEVENS-JOHNSON SYNDROME, HYPERSENSITIVITY REACTION AND TOXIC EPIDERMAL NECROLYSIS. IMMEDIATELY DISCONTINUE TREATMENT WITH ISENTRESS AND OTHER SUSPECT AGENTS IF SEVERE HYPERSENSITIVITY, SEVERE RASH, OR RASH WITH SYSTEMIC SYMPTOMS OR LIVER AMINOTRANSFERASE ELEVATIONS DEVELOPS AND MONITOR CLINICAL STATUS, INCLUDING LIVER AMINOTRANSFERASES CLOSELY.

MONITOR FOR IMMUNE RECONSTITUTION SYNDROME.

INFORM PATIENTS WITH PHENYLKETONURIA THAT THE 100 MG AND 25 MG CHEWABLE TABLETS CONTAIN PHENYLALANINE. 

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