Drug Failure

Drug Failure

Drug failure is the failure of a drug to continue to do the job it is supposed to do. With regards to HIV/AIDS, the American Medical Association defines drug failure as the following:

• Inadequate viral suppression (inability to keep HIV RNA at an "undetected" level)
• Unsatisfactory increase in CD4+ count
• Progression of clinical symptoms due to immune dysfunction

Most practitioners focus on the first of these 3 criteria—the change in viral load. In many cases, the decision to change therapy is somewhat subjective. Most practitioners do not recommend changing therapy solely on the basis of the CD4+ count, since the relationship between a change in CD4+ and drug effectiveness is not clear.

It is important to make an effort to determine what has caused the drug failure. The primary cause of drug failure is lack of adherence, which leads to resistance. If drug failure is due to dose adherence problems, what can be done to help the patient follow the regimen more carefully? Is drug failure due to adverse drug interactions or other pharmacological problems? Is it due to resistance that has evolved despite that fact that the patient has faithfully adhered to the dosing schedule? These are important questions to ask.