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Therapeutic Drug Monitoring (TDM) Often Brings Clinical Benefits
Adequate plasma concentrations of antiretroviral
drugs are key to achieving and maintaining long-term suppression
of HIV replication. Multiple factors may influence drug levels, causing increases or
reductions that may, respectively, result in toxicity or virological
failure.
Therapeutic
drug monitoring (TDM) might help to detect and correct such abnormalities.
In this study, researchers evaluated the
usefulness of TDM in the care of HIV-infected patients in an out-patient
clinical setting.
All the requests for TDM of protease
inhibitors (PIs) and non
nucleoside reverse transcriptase inhibitors (NNRTIs) for patients attending an HIV out-patient clinic in Madrid, Spain
from October 2000 to August 2003 were analyzed.
Blood samples were collected before the morning
dose and drug concentrations were measured by high performance liquid
chromatography by ultraviolet waves (HPLC-UV).
Results
· A
total of 151 requests from 137 patients were assessed.
· The
reasons for requesting TDM were drug toxicity (59%), virological
failure (39%) and possible drug interactions (2%).
· NNRTI
levels were more often requested because of toxicity, while PI levels
were more often requested because of virological failure.
· Elevated drug
levels were confirmed in 36% of patients with suspected drug toxicity,
while sub-therapeutic levels were found in 37% of patients failing
virologically.
· Based on the
results of TDM, dose modifications were made in 37% of patients,
allowing correction of such abnormalities in 80% of cases.
· Moreover,
adequate plasma concentrations were confirmed in 79% of patients
whose levels were assessed again.
The authors conclude, “Therapeutic
drug monitoring may be a useful tool to identify toxic levels of
NNRTI and subtherapeutic concentrations of PI. Dose adjustments
following TDM may ameliorate drug-related toxicities or improve
virological response rates.”
09/23/05
Reference
A L Rendó, M Núñez and others. Clinical benefit of interventions driven by therapeutic drug
monitoring. HIV Medicine 6(5): 360-365. September 2005.
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