Isentress (raltegravir) is an antiretroviral medicine used as part of combination treatment for HIV-1 infection. It belongs to the integrase inhibitor class and works by blocking HIV integrase, an enzyme the virus uses to insert its genetic material into human cells. Without integration, HIV cannot establish a permanent infection.

Isentress HD (600 mg) allows for a once-daily dosing option (two 600 mg tablets once daily), while the standard 400 mg formulation is taken twice daily.

Isentress 400 mg: take one tablet twice daily (every 12 hours), with or without food.

Isentress HD 600 mg: take two 600 mg tablets once daily, with or without food.

Do not substitute the 400 mg and 600 mg formulations for each other without advice from your HIV doctor. Isentress must always be used in combination with other HIV medicines.

For twice-daily (400 mg): if you remember within 12 hours, take it straight away. If closer to the next dose, skip and continue as normal.

For once-daily HD: take as soon as you remember the same day. If you only remember the next day, skip and continue normally. Never double dose.

Contact your HIV specialist or a poison control centre immediately.

• Store at room temperature, below 30°C
• Keep in the original container with the lid firmly closed
• Keep out of reach of children

Raltegravir is generally well tolerated.

Common side effects:

• Nausea
• Headache
• Fatigue
• Dizziness
  

Less common but important:

• Elevated creatine kinase: can cause muscle pain or weakness. Report significant muscle aches
• Rhabdomyolysis (severe muscle breakdown): rare but serious. Seek urgent help if you have extreme muscle pain or dark urine
• Psychiatric symptoms: depression and insomnia have been reported rarely

Blood tests to monitor liver function and blood count are done regularly.

• Antacids and supplements containing aluminium, magnesium, calcium, or iron: these can bind to raltegravir and significantly reduce absorption. Timing relative to your dose matters
• Rifampicin: significantly reduces raltegravir levels. If you take or need to start rifampicin, let your HIV doctor know, as your regimen may need reviewing
  

Isentress generally has fewer drug interactions than many other antiretrovirals.

Why is Isentress sometimes chosen for patients starting HIV treatment?

Raltegravir has a strong safety profile, a low burden of drug interactions, and no known effect on kidney function, liver enzymes, or lipids. This makes it particularly useful for people who take many other medicines or who have underlying kidney, liver, or cardiovascular conditions.

Can I take it with antacids?

Antacids and products containing aluminium, magnesium, calcium, or iron can bind to raltegravir and significantly reduce how much is absorbed. If you use antacids regularly, mention this to your pharmacist before starting Isentress so they can advise on how to manage it.

Ace provides accurate and independent information medically reviewed on prescription medications. This material is provided for educational purposes only and is not intended for medical advice, diagnosis or treatment.