Understanding Isentress Drug Interactions

When you're taking Isentress (Raltegravir) as part of your HIV treatment, knowing which medications, supplements, and foods can interact with it is essential. Drug interactions can reduce the effectiveness of your HIV treatment or increase the risk of side effects.

Compared to some other antiretroviral drug classes, Isentress has a relatively manageable interaction profile — but there are still several important ones you need to know about.

How Drug Interactions Work with Isentress

Isentress is primarily metabolized through a process called UGT1A1-mediated glucuronidation. Unlike many HIV drugs that are processed by the cytochrome P450 (CYP450) enzyme system, Isentress uses a different metabolic pathway. This means it has fewer interactions with drugs processed by CYP450 enzymes.

However, medications that induce (speed up) or inhibit (slow down) UGT1A1 can still affect Raltegravir levels in your body. Additionally, some substances can affect absorption — reducing the amount of Isentress that enters your bloodstream.

Medications That Interact with Isentress

Rifampin (Major Interaction)

Rifampin is the most significant drug interaction with Isentress. Rifampin is commonly used to treat tuberculosis (TB) and can reduce Raltegravir blood levels by approximately 40-60%.

• What to do: If you must take both medications, your doctor should increase the Isentress dose to 800 mg twice daily (double the standard dose).
• Never adjust the dose yourself — this must be managed by your healthcare provider.

This interaction is particularly relevant because HIV and TB co-infection is common in many parts of the world.

Strong UGT1A1 Inducers

Other medications that induce UGT1A1 can also decrease Raltegravir levels, potentially reducing its effectiveness:

• Phenytoin (seizure medication)
• Phenobarbital (seizure/sedative medication)

If you take any of these medications, your doctor will need to monitor your viral load closely and may adjust your treatment plan.

Tipranavir/Ritonavir

The HIV protease inhibitor combination of Tipranavir boosted with Ritonavir may reduce Raltegravir levels. Your doctor should consider this when designing your antiretroviral regimen.

Orlistat (Weight Loss Medication)

Orlistat (brand names Xenical, Alli) may decrease Raltegravir absorption. Cases of loss of virologic control have been reported when patients took Orlistat with Raltegravir-containing regimens. Discuss with your doctor if you're considering weight management medications.

Supplements and Over-the-Counter Products

Aluminum and Magnesium-Containing Antacids (Major Interaction)

This is one of the most important interactions to know about. Antacids containing aluminum and/or magnesium significantly reduce Isentress absorption — in some cases by up to 50% or more.

• Products to avoid: Maalox, Mylanta, and similar aluminum/magnesium antacids
• Do not take these at the same time as Isentress

Calcium Carbonate Antacids

Calcium-based antacids (like Tums) may also reduce Isentress absorption, though the effect is less dramatic than with aluminum/magnesium products. Use caution and discuss with your doctor.

Calcium and Iron Supplements

While not as extensively studied as antacid interactions, mineral supplements containing calcium or iron may potentially affect absorption. Take these at a different time than your Isentress dose if possible.

St. John's Wort

While St. John's Wort is a well-known inducer of drug metabolism for many HIV medications, its specific effect on Raltegravir is less pronounced because of the different metabolic pathway. However, it's still generally recommended to avoid St. John's Wort when taking any antiretroviral medication, as it can affect other drugs in your regimen.

Food and Drink Interactions

Isentress has relatively few food interactions, which is one of its advantages:

• Isentress 400 mg tablets — Can be taken with or without food. No specific food restrictions.
• Isentress HD 600 mg tablets — Must be taken with food to ensure adequate absorption. Taking Isentress HD on an empty stomach can significantly reduce drug levels.

There are no specific restrictions on alcohol with Isentress itself, though alcohol can interact with other medications in your HIV regimen and can affect your overall health and immune function. Discuss alcohol use with your healthcare provider.

What to Tell Your Doctor

Before starting Isentress — and at every follow-up visit — make sure your doctor knows about:

• All prescription medications you take, including antibiotics, seizure medications, and other HIV drugs
• Over-the-counter medications, especially antacids and pain relievers
• Vitamins and supplements, including calcium, iron, and herbal products
• Any new medications added by other providers (dentists, urgent care, specialists)

It's especially important to inform any non-HIV healthcare provider that you take Isentress before they prescribe new medications. Pharmacists can also help screen for interactions when you fill prescriptions.

For more about what Isentress is and how it's taken, see our complete Isentress guide. For side effect information, visit our side effects guide.

Final Thoughts

Isentress has a more favorable drug interaction profile than many other antiretroviral medications, but there are still critical interactions to be aware of — particularly with Rifampin and aluminum/magnesium antacids. The key is communication: make sure every healthcare provider involved in your care knows what you're taking.

Keeping an up-to-date medication list and sharing it at every appointment is one of the simplest and most effective things you can do to stay safe on Isentress.

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