Therapeutic Drug Monitoring (TDM) means monitoring of drug levels in the blood before, during or after drug treatment. TDM is an excellent tool to aid optimisation of drug regimens for the individual patient, to help increase efficacy and avoid drug-related toxicity. Lab 21 provides TDM services for a wide range of drugs and drug types in a variety of disease areas (see tables below).
Situations calling for TDM include:
- Significant inter- and intra-individual variability in plasma drug concentration at a fixed dose
- A narrow therapeutic window, or index, i.e. the level at which they are effective is very close to the level at which they are toxic
- A high toxicity profile (dose-limiting toxicity)
- Drug-drug or drug-food interaction
- Pediatric patients, pregnancy
- Extremes of BMI
- Complex clinical situations (e.g. liver impairment, co-infections, drug interactions, treatment failure)
- Suspected non-adherence
Lab 21 is committed to providing the highest quality services to our customers, and test turnaround time is only 14 working days from the receipt of sample.
Not just a number
Lab 21 will accept all samples taken >4h after drug administration. If they are not trough samples we will estimate the trough concentration, where possible, either by projection based on population half-life data or based on population PK (percentile) data. Peak samples may also be useful, but <4hr will not generate a report which can extrapolate trough data.
Viral Hepatitis TDM from Lab 21
Please see the tables below for the full range of Hepatitis drugs the service can analyse.
As reviewed by Sauvage et al, 2009, Ribavirin has a large distribution volume, a long half-life and large inter-individual pharmacokinetic variability. Several studies suggest that there is a poor dose-concentration relationship for Ribavirin and that the concentration of the drug in the blood, rather than the dose, is associated with effectiveness of the therapy. Anemia may also be caused by ribavirin in a dose-dependent manner. Therefore, therapeutic drug monitoring of Ribavirin plasma concentrations can be useful for tailoring individual dosing, as well as for monitoring adherence.
Tenofovir is a drug used to treat both HIV and HBV, and TDM for tenofovir is useful to monitor adherence to the drug regimen. It may also be useful for monitoring of drug levels in the plasma in e.g. complex clinical situations.
HCV TDM services available at Lab 21
|Commercial Name||Active Drug|
|Tenofovir and Emitricitabine|
Not provided under our UKAS accreditation.
Please see our Accreditation page for full scope of accredited testing.
Sauvage F-L, Stanke-Labesque F, Gagnieu M-C et al. Feasibility of ribavirin monitoring in Hepatitis C. Ther Drug Monit, 2009; 31(3): 374–381.