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Indinavir

Other Names: IDV, Crixivan®
Manufacturer: Merck and Company

What is it?

Indinavir belongs to a group of drugs known as protease inhibitors. It is used to treat HIV, a retrovirus. Retroviruses use the genetic material in the body’s cells to produce more virus which can infect other cells.

How does it work?

Indinavir interferes with the life cycle of HIV to stop it from producing more virus. Specifically, indinavir ties up the protease enzyme, which slows the production of new virus to prevent other cells from becoming infected.

How do I take it?

  • Indinavir is available as 200 mg, 333 mg, and 400 mg capsules.
  • The dose of indinavir varies depending upon what other medications you take with it. Your dose will be as listed below:

If you take indinavir with ritonavir, you can take the medication with food. Otherwise, it is recommended that this drug be taken on an empty stomach (1 hour before or 2 hours after meals). If you are unable to tolerate indinavir on an empty stomach, you may take this drug with a “light snack” that is low in protein and fat. Examples include coffee, tea, fruit juices (except grapefruit juice), skim milk, dry toast with jelly, or corn flakes. Ask the pharmacist for a list of additional snacks.

A possible side effect of indinavir is the formation of kidney stones (nephrolithiasis). In order to prevent this side effect, you should drink at least 1.5 liters (eight 8-ounce glasses) of fluid daily . Water and fruit juices are the best choices for meeting this fluid intake requirement.

It is extremely important that you take indinavir and your other antiretroviral medications exactly as directed. You should set up a system that will help you remember to take your medicines so that you do not miss any doses. If you miss a dose, take it as soon as possible and space the remaining doses out over the rest of the day. However, if you skip a dose, do not take two doses at once. Do not stop taking the medication for any reason at any time unless you are directed to do so by your provider. If you are unable to continue taking your medication due to side effects, you should contact your provider immediately.

Special Considerations

  • Indinavir should be stored at controlled room temperature in a dry place, out of reach of children.
  • Indinavir is very sensitive to moisture; therefore, the plastic desiccant supplied with the medication should be left in the medication bottle.

Interactions

Some drugs taken together may have interactions that cause illness or impair the effectiveness of the drugs. Indinavir has a number of serious drug interactions. You need to be familiar with the names of medications that you are taking and compare them to the medications listed below. Make sure that everyone who is prescribing or dispensing medications to you knows that you are taking indinavir.

Drugs that interact with indinavir:

  • antacids (Mylanta®, Maalox®, Tums®)
  • astemizole (Hismanal®)
  • cisapride (Propulsid®)
  • ketoconazole (Nizoral®)
  • nefazodone (Serzone®) and other antidepressants
  • midazolam (Versed®)
  • rifampin, rifabutin
  • terfenadine (Seldane®)
  • triazolam (Halcion®)

Many other drugs may interact with indinavir so you must tell your provider about all medications you are currently taking. This includes any medications that you may take on an 'as needed' basis, such as sleeping pills or pain medications and herbal or natural medicines.

Grapefruit juice should be avoided as it has been shown to decrease the levels of indinavir in the bloodstream. Other antiretroviral drugs may increase or decrease (drugs such as nevirapine or efavirenz) the amount of indinavir that is in your body. The dose of indinavir or other antiretroviral medications may need to be adjusted to compensate for this interaction.

Side Effects

Not everyone experiences side effects. When they do occur, they may be mild, moderate or severe. Some side effects cannot be felt by the patient but can be found through laboratory tests, so it is important to see your clinician regularly for checkups so that side effects can be detected early and treated.

One of the most serious side effects that has been seen in some patients who have taken indinavir is the formation of kidney stones (nephrolithiasis). Two signs of kidney stone formation are pain in the flank (lower back area), and blood in the urine. If you develop these types of symptoms while taking indinavir, call your clinician immediately. To help prevent kidney stones, it is very important that you drink at least 1.5 liters of fluid every day.

The most common side effects seen with indinavir are nausea, vomiting, diarrhea, abdominal pain, and heartburn. These side effects may occur more frequently when you first start taking indinavir, but often decrease over time. Indinavir may also cause headaches, difficulty sleeping (insomnia), muscle weakness, and taste disturbances. Also, it has been noted that hemophiliacs have an increased risk of bleeding while taking indinavir.

Increases in blood sugar or the development of diabetes has been reported in a small number of patients taking protease inhibitors. Symptoms include increased thirst or hunger, weight loss, increased need to urinate, fatigue, or dry, itchy skin. Please contact your clinician if any of these side effects occur.

Also, a condition called lipodystrophy (abnormal use of fats in the body) has been reported in patients taking protease inhibitors. Symptoms vary among individuals, but they may include accumulation of fat tissue in the stomach area or the upper back, and a loss of mass in other areas of the body. Some people have experienced increases in cholesterol and triglycerides that have required the use of lipid lowering medications.

The benefits of taking protease inhibitors far outweigh the risk of developing lipodystrophy or diabetes. Therefore, at this time, we strongly encourage you to take your medications exactly as prescribed. Notify your clinician if any of these side effects are bothersome and may prevent you from taking your medication.

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