B.C. Centre for Excellence in HIV/AIDS

Guidelines

Drug resistance testing
Drug resistance testing has three primary clinical functions: identifying drug resistance in patients failing therapy; identifying primary resistance in newly identified HIV patients; and identifying failing patients who do not have drug resistant HIV.

Patients failing therapy
HIV infected patients receiving antiretroviral therapy with rising plasma viral loads of greater than 250 copies/mL could benefit from drug-resistance testing to establish HIV-sensitivity to the antiretroviral drugs they are receiving. With drug-resistance data, physicians can rationally select a new combination therapy for their patients.

Newly identified HIV patients
For newly identified HIV-infected patients, drug-resistance can determine whether drug-resistant HIV has been acquired. Physicians can then initiate the most suitable therapy for their patients.

Patients failing therapy who do not have drug resistant HIV
Drug resistance testing can identify HIV-infected patients who are failing antiretroviral therapy, but who do not have drug-resistant HIV. These patients may benefit from drug-level testing to establish problems with drug absorption or metabolism.

Therapeutic Drug Monitoring
Therapeutic Drug Monitoring (TDM), also known as drug concentration monitoring, is currently available for non nucleoside reverse transcriptase inhibitors and protease inhibitors. TDM is typically performed on an inpatient basis following observed dosing. Plasma samples are usually obtained at pre-dosing, one hour post-dosing and every two hours thereafter until the time of the next dose.

Therapeutic drug monitoring should be considered:

in all patients receiving multiple drug rescue therapy, or an unusual regimen
in selected patients receiving complex regimens with potential drug to drug interactions (e.g., anti-tuberculosis drugs).
in selected patients presenting with unexplained treatment failure.
in selected patients presenting with unexplained toxicity.
in selected patients with abnormal liver or kidney function.
in selected patients during pregnancy.
in selected patients at the extremes of body size distribution.
After a dosage adjustment is made, based on TDM.


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	PRINT Laboratory Guidelines Drug resistance testing Drug resistance testing has three primary clinical functions: identifying drug resistance in patients failing therapy; identifying primary resistance in newly identified HIV patients; and identifying failing patients who do not have drug resistant HIV. Patients failing therapy HIV infected patients receiving antiretroviral therapy with rising plasma viral loads of greater than 250 copies/mL could benefit from drug-resistance testing to establish HIV-sensitivity to the antiretroviral drugs they are receiving. With drug-resistance data, physicians can rationally select a new combination therapy for their patients. Newly identified HIV patients For newly identified HIV-infected patients, drug-resistance can determine whether drug-resistant HIV has been acquired. Physicians can then initiate the most suitable therapy for their patients. Patients failing therapy who do not have drug resistant HIV Drug resistance testing can identify HIV-infected patients who are failing antiretroviral therapy, but who do not have drug-resistant HIV. These patients may benefit from drug-level testing to establish problems with drug absorption or metabolism. Therapeutic Drug Monitoring Therapeutic Drug Monitoring (TDM), also known as drug concentration monitoring, is currently available for non nucleoside reverse transcriptase inhibitors and protease inhibitors. TDM is typically performed on an inpatient basis following observed dosing. Plasma samples are usually obtained at pre-dosing, one hour post-dosing and every two hours thereafter until the time of the next dose. Therapeutic drug monitoring should be considered: in all patients receiving multiple drug rescue therapy, or an unusual regimen in selected patients receiving complex regimens with potential drug to drug interactions (e.g., anti-tuberculosis drugs). in selected patients presenting with unexplained treatment failure. in selected patients presenting with unexplained toxicity. in selected patients with abnormal liver or kidney function. in selected patients during pregnancy. in selected patients at the extremes of body size distribution. After a dosage adjustment is made, based on TDM.