Isentress (Raltegravir) is a prescription integrase strand transfer inhibitor (INSTI) used in combination with other antiretroviral medications to treat HIV-1 infection in adults and children.

What Is Isentress?

Isentress is the brand name for Raltegravir, a medication manufactured by Merck & Co. It belongs to a class of HIV drugs called integrase strand transfer inhibitors (INSTIs). First approved by the FDA in 2007, Isentress was the first integrase inhibitor available for HIV treatment, representing a significant advance in antiretroviral therapy.

Isentress works by blocking HIV integrase, an enzyme the virus needs to insert its genetic material into human cells. By preventing this step, the medication stops HIV from replicating. For a more detailed explanation, see our article on how Isentress works.

Isentress does not cure HIV. It is used as part of a combination regimen (usually with two or more other antiretroviral drugs) to reduce viral load and help maintain immune function.

What Is Isentress Used For?

Isentress is FDA-approved for:

• Treatment of HIV-1 infection in adults and pediatric patients (from birth, weighing at least 2 kg) in combination with other antiretroviral agents

It may also be used off-label in certain situations:

• Post-exposure prophylaxis (PEP) — As part of a combination regimen following potential HIV exposure
• Research settings — Investigated in pre-exposure prophylaxis (PrEP) studies

Isentress is used in both treatment-naive patients (those starting HIV treatment for the first time) and treatment-experienced patients (those switching from another regimen).

How Is Isentress Taken?

Isentress is available in several formulations to accommodate different patient needs:

For Adults

• Isentress 400 mg film-coated tablets — Taken twice daily (one tablet in the morning and one in the evening). Can be taken with or without food.
• Isentress HD 600 mg film-coated tablets — Taken as two tablets (1,200 mg total) once daily. Must be taken with food. This once-daily option is available for treatment-naive patients or those who are virologically suppressed on a twice-daily regimen.

For Children

• 100 mg chewable tablets — Dosed by weight. May be chewed or swallowed whole.
• Granules for oral suspension — 100 mg per packet, mixed with water. Designed for infants and young children.

Important: The chewable tablets and film-coated tablets are not interchangeable. Do not substitute one for the other without your doctor's guidance.

General Tips

• Take Isentress at the same time(s) every day
• Do not skip doses — missing doses can lead to drug resistance
• If you miss a dose, take it as soon as you remember, but do not double up
• Store at room temperature

Who Should Not Take Isentress?

Isentress is contraindicated in patients with a known hypersensitivity to Raltegravir or any component of the formulation. Additionally, use with caution in the following situations:

• History of rhabdomyolysis or myopathy — Isentress has been associated with muscle-related side effects in rare cases. Your doctor should weigh the risks if you have a history of these conditions.
• Concurrent use with Rifampin — Rifampin significantly reduces Raltegravir levels. If coadministration is necessary, the Isentress dose must be increased to 800 mg twice daily. See our drug interactions guide for details.
• Aluminum or magnesium-containing antacids — These significantly reduce Isentress absorption and should be avoided.

Isentress is considered one of the preferred integrase inhibitors during pregnancy per DHHS guidelines. It does not require dose adjustment for renal impairment or mild-to-moderate hepatic impairment.

For a full overview of side effects, read our guide on Isentress side effects.

How Much Does Isentress Cost?

The cost of Isentress depends on your insurance coverage and pharmacy:

• Cash price (without insurance): Approximately $1,900 to $2,500 per month for a 30-day supply of brand-name Isentress.
• With insurance: Most commercial insurance plans and Medicare Part D cover Isentress, though it's often placed on a specialty or non-preferred brand tier. Prior authorization may be required. Medicare Part D has a $2,000 annual out-of-pocket cap as of 2025.
• Generic availability: Lupin received FDA approval for generic Raltegravir in May 2025, but market availability may still be limited as of early 2026.

Ways to Save

• Merck Copay Savings Card — Up to $6,800 per year in savings for commercially insured patients.
• Merck Patient Assistance Program — Free medication for eligible uninsured or underinsured patients through merckhelps.com.
• Ryan White/ADAP Programs — Federal and state programs that cover HIV medications for qualifying patients.

For a complete breakdown of savings options, see our guide to saving money on Isentress.

Final Thoughts

Isentress has been a cornerstone of HIV treatment since it was first approved in 2007. It remains an effective and well-tolerated option for adults and children living with HIV-1, with multiple dosage forms and a safety profile that's been studied for nearly two decades.

Whether you're starting HIV treatment for the first time or considering a switch to Isentress, work closely with your healthcare provider to determine the right regimen for you.

Need help finding Isentress at a pharmacy? Search on Medfinder to check availability near you.