Phase III clinical trials tend to enroll carefully selected patients who have few or mild-to-moderate pre-existing health conditions. In practice, once a drug is licensed, a wide variety of patients, some of whom may have multiple health conditions, may receive a new drug. One such pre-existing condition is HIV co-infection. As HIV-positive people will most likely be taking potent combination anti-HIV therapy (commonly called ART or HAART), it is essential to study potential interactions between drugs used for HIV and drugs used for HCV.
World-renowned pharmacologist David Burger, PhD, has assembled and reviewed data on many potential interactions that could occur between different drugs. Here is a summary of recent research that he presented.
Boceprevir - Impact on HIV protease inhibitors
In experiments used to assess interactions between drugs, here are the main findings:
- levels of atazanavir-ritonavir fell by 35% when used with boceprevir
- levels of lopinavir-ritonavir (in Kaletra) fell by 34% when used with boceprevir
- levels of darunavir-ritonavir fell by 44% when used with boceprevir
These changes are so great that Dr. Burger notes that boceprevir should not be used with these HIV drugs.
Levels of this drug increased by 1% when used with boceprevir.
Boceprevir reduced etravirine levels by 23%.
Efavirenz reduced boceprevir levels by 19%—these should not be used together.
Effect of HIV drugs on boceprevir
In experiments on people, the following changes occurred:
- atazanavir-ritonavir reduced boceprevir levels by 5%
- lopinavir-ritonavir reduced boceprevir levels by 34%
- darunavir-ritonavir reduced boceprevir levels by 32%
- etravirine reduced boceprevir levels by 10%.
Bocepravir drug interaction summary
Dr. Burger recommended that the following courses of action be taken by doctors who are contemplating prescribing boceprevir to people who are co-infected with HIV and HCV:
- tenofovir increases boceprevir levels by 8%—these drugs may be used together
- etravirvine may be used with boceprevir
- raltegravir may be used with boceprevir
The following drugs should not be used with boceprevir:
- efavirenz reduces boceprevir levels by 19%—these should not be used together
Each person will likely be taking several other drugs to treat complications of HCV (or HIV infection), therefore much more information about drug interactions is needed. Until the results of large clinical trials conducted by the ACTG and ANRS are completed and consensus has emerged about which drugs to use, we urge physicians who are contemplating prescribing these or other therapies to seek guidance from regulatory authorities, consult the necessary product monographs or speak with other experts, particularly pharmacologists and other specialists who are experienced in treating co-infected patients.
— Sean R. Hosein
Burger DM. Interactions between antiretrovirals and direct acting antivirals. In: Program and abstracts of the 8th International Workshop on HIV and Hepatitis Co-infection, 30 May–1 June 2012, Madrid, Spain.