Patients who have been previously treated with, and possibly resistant to other protease inhibitors, may require an increased dose of the coformulated capsules of ABT-378 and ritonavir (ABT-378/r) when given with efavirenz.
The warning comes after the release of data in the US by Abbott Laboratories showing an interaction between its new protease inhibitor ABT-378 (also known as lopinavir) and efavirenz.
Efavirenz was found to lower the levels of ABT-378 by about 20-40%. The Cmin of ABT-378 was reduced by 40% and the area under the curve, or amount of drug exposure over time, was reduced by 20%.
Each capsule contains 133.3 mg ABT-378 and 33.3 mg ritonavir. The current dose of ABT-378/r is three capsules twice a day. Abbott officials recommend that protease inhibitor experienced patients increase the dose of ABT-378/r to four capsules twice a day, when taken with efavirenz.
Patients receiving ABT-378/r through Abbott UK's Long Term Safety Study are likely to be highly protease inhibitor experienced. If you are taking efavirenz as part of your regimen, a dose increase will be necessary so that you receive the full benefit of ABT-378/r. Abbott UK recommends that the dose of ABT-378 should be increased to four capsules twice a day in this situation.
Abbott is in the process of amending the protocol to allow for the ABT-378/r dose adjustment, giving patients who are on efavirenz additional ABT-378/r as necessary.