References UK clinical guidance from the NHS, the British HIV Association (BHIVA), and the British Association for Sexual Health and HIV (BASHH). Last updated: April 2026.
Lopinavir/ritonavir (brand name Kaletra) is a combination protease inhibitor tablet used to treat HIV. It combines lopinavir (the active HIV drug) with a small amount of ritonavir (a pharmacokinetic booster) in a single tablet. While newer drugs have largely replaced Kaletra in first-line treatment, it remains an option in certain situations.
How Does Kaletra Work?
Lopinavir blocks HIV protease, preventing the virus from producing functional proteins needed to create new viral particles. Ritonavir inhibits the liver enzyme that breaks down lopinavir, keeping blood levels high enough for twice-daily dosing.
Dosage
- Standard: 2 tablets (each containing 200mg lopinavir + 50mg ritonavir) twice daily
- Alternative: 4 tablets once daily (for some patients)
- Can be taken with or without food
- Tablets must be swallowed whole — don’t crush or split
Side Effects
- Diarrhoea (very common — the most frequently reported side effect)
- Nausea
- Abdominal pain
- Headache
- Raised cholesterol and triglycerides
- Insulin resistance / raised blood sugar
- Raised liver enzymes
When Is Kaletra Still Used?
- In resource-limited settings where newer drugs are less available
- In pregnancy (has extensive safety data)
- In children (liquid formulation available)
- When integrase inhibitors cannot be used
- In second-line regimens after treatment failure
Drug Interactions
Kaletra has numerous drug interactions due to ritonavir’s strong inhibition of CYP3A4. Always tell your doctor about all medications you take. Some drugs are contraindicated (e.g., simvastatin, St John’s Wort, certain antiarrhythmics).
Read more: What is HIV? | Starting HIV treatment | Drug interactions
Frequently Asked Questions
Is Kaletra still prescribed?
Yes, though less commonly as first-line treatment. Modern integrase inhibitor-based regimens are preferred due to better tolerability and fewer drug interactions. Kaletra remains important in specific clinical situations.
Why does Kaletra cause diarrhoea?
Diarrhoea is a well-known side effect of lopinavir and, more significantly, ritonavir. It usually improves over the first few weeks but persists for some patients, which is a common reason for switching to a different regimen.
Related reading
- Choosing the Right PrEP Drug: Truvada vs Descovy
- Dovato for HIV: A Two-Drug Regimen
- Triumeq for HIV: A Straightforward Guide
- Efavirenz for HIV: An Older NNRTI Still in Use
- Eviplera: How This Anti-HIV Drug Works
Sources
- NHS — Sexual health conditions
- BASHH — UK clinical guidelines for STI management
- British HIV Association (BHIVA) — HIV treatment guidelines
- Terrence Higgins Trust — sexual health information
- UK Health Security Agency — STI surveillance data
Steve Page is a recognised expert on Sexually Transmitted Diseases (STDs) and STD treatments, having published numerous articles in peer-reviewed journals and presented his research at conferences around the world. He has an in-depth understanding of the latest medical research on STDs, and is an advocate for the development of new treatments and protocols to improve the health of those affected. In addition to his research, he has dedicated his career to understanding the causes and symptoms of STDs, as well as how to best treat those impacted.
