Some useful terms and what they mean

Here is a list of terms that are commonly used when talking about HIV and its treatment. Click the terms below to learn about:

    • CD4 cells (also known as T cells) are white blood cells that fight infection. The number of T cells in a sample of blood is your T-cell count.
    • An important, soft, waxy substance found in your blood. Cholesterol comes in two forms: "good" (HDL) and "bad" (LDL).
    • When a disease or weakness has been with you for a long time.
    • When the condition of your liver gets worse. You cannot live without your liver. It removes harmful chemicals from your blood; fights infection; helps you digest food; and stores nutrients, vitamins, and energy.
    • A form of liver disease caused by the hepatitis B virus. You get it by coming in contact with body fluids, like blood, semen, and vaginal fluids of an infected person. It can lead to permanent liver damage and even liver cancer.
    • A form of liver disease caused by the Hepatitis C virus. You can get it by having unprotected sex or sharing needles with an infected person. It can lead to permanent liver damage and even liver cancer.
    • When HIV makes your immune system so weak, it has trouble fighting common infections.
    • Drugs you can buy without a prescription.
    • When a medicine has a different effect on you than it was meant to have.
      Side effects can be unpleasant and can make it difficult for you to do your
      daily activities.
    • When the amount of HIV in your blood is so small, the lab test can hardly tell it’s there. This does not mean that your HIV is “cured.” And it is still possible to pass the virus on to someone—even if it is undetectable.

Click here for a customizable list of questions to bring up during your next healthcare visit.


Talk to your healthcare team about your hopes for the future and any concerns about therapy.

ISENTRESS is an HIV medicine that, when used with other
HIV medicines, may reduce the amount of HIV in your blood and
help increase the number of CD4 (T) cells.

ISENTRESS is a prescription HIV-1 medicine used with other antiretroviral medicines to treat human immunodeficiency virus (HIV-1) infection in people 4 weeks of age and older. HIV is the virus that causes AIDS (Acquired Immune Deficiency Syndrome).

It is not known if ISENTRESS is safe and effective in babies under 4 weeks of age.

The use of other medicines active against HIV-1 in combination with ISENTRESS may increase your ability to fight HIV.

ISENTRESS does not cure HIV-1 infection or AIDS.

You must stay on continuous HIV therapy to control HIV-1 infection and decrease HIV-related illnesses.


Some people who take ISENTRESS develop serious skin reactions and allergic reactions that can be severe, and may be life-threatening or lead to death. (cont'd below)

Click here for more important risk information about ISENTRESS



If you develop a rash with any of the following symptoms, stop using ISENTRESS and call your doctor right away: fever, generally ill feeling, extreme tiredness, muscle or joint aches, blisters or sores in mouth, blisters or peeling of skin, redness or swelling of the eyes, swelling of the mouth or face, problems breathing.

Sometimes allergic reactions can affect body organs, such as your liver. Call your doctor right away if you have any of the following signs or symptoms of liver problems: yellowing of your skin or whites of your eyes, dark or tea-colored urine, pale-colored stools (bowel movements), nausea or vomiting, loss of appetite, pain, aching or tenderness on the right side of your stomach area.

Changes in your immune system (Immune Reconstitution Syndrome) can happen when you start taking HIV-1 medicines. Your immune system may get stronger and begin to fight infections that have been hidden in your body for a long time. Tell your doctor right away if you start having new symptoms after starting your HIV-1 medicine.

People taking ISENTRESS may still develop infections or other conditions associated with HIV infections.

The most common side effects of ISENTRESS include: trouble sleeping, headache, dizziness, nausea, and tiredness. Less common side effects include: depression, hepatitis, genital herpes, herpes zoster including shingles, kidney failure, kidney stones, indigestion or stomach area pain, vomiting, suicidal thoughts and actions, and weakness.

Tell your doctor before you take ISENTRESS if you have a history of a muscle disorder called rhabdomyolysis or myopathy or increased levels of creatine kinase in your blood.

Tell your doctor right away if you get unexplained muscle pain, tenderness, or weakness while taking ISENTRESS. These may be signs of a rare serious muscle problem that can lead to kidney problems.

These are not all the possible side effects of ISENTRESS. For more information, ask your doctor or pharmacists. Tell your doctor if you have any side effect that bothers you or that does not go away.

Tell your doctor about all your medical conditions, including if you have any allergies, are pregnant or plan to become pregnant, or are breastfeeding or plan to breastfeed. ISENTRESS is not recommended for use during pregnancy. Do not breastfeed if you take ISENTRESS. Women with HIV should not breastfeed because their babies could be infected with HIV through their breast milk.

Tell your doctor about all the medicines you take, including, prescription and over-the-counter medicines, vitamins, and herbal supplements. Some medicines interact with ISENTRESS. Do not start taking a new medicine without telling your healthcare provider. Your healthcare provider can tell you if it is safe to take ISENTRESS with those other medicines.

You are encouraged to report negative side effects of prescription drugs to the FDA. Visit, or call FDA at 1-800-FDA-1088.

Please read the accompanying Patient Information and Instructions for Use for ISENTRESS and discuss them with your doctor. The physician Prescribing Information also is available.

Having trouble paying for your Merck medicine? Merck may be able to help.

Brands mentioned are the trademarks of their respective owners.

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