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.

Find out more

Please contact us to discuss your needs with our clinical team.

HIV TDM from Lab 21

Typically 20 – 50% of patients in clinic have sub-therapeutic plasma concentrations of PIs and NNRTIs, while the inter-individual variability in plasma concentrations is immense (=100-fold difference) despite standard dosing. Therapeutic drug monitoring (TDM) is used to optimise drug regimens for the individual patient by increasing efficacy and avoiding drug-related toxicity.

Not just a number

In addition to the concentration of the requested drugs, Lab 21 HIV TDM results include a clinical interpretation based on a validated algorithm for the majority of drugs. A database of reporting algorithms has been created by the University of Liverpool and associates. The algorithms are developed, reviewed and updated by an international panel of experts in pharmacology and HIV therapy. Where possible, each Therapeutic Drug Monitoring report supplements the drug concentration level(s) with comments designed to assist the treating physician in interpreting the result.

Not just trough samples

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, in certain cases.


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.

TDM services available at Lab 21

[vc_table vc_table_theme=”simple”][b]Commercial%20Name,[b]Active%20Drug|Combivir,Lamivudine%20and%20Zidovudine|Emtriva,Emtricitabine|Epivir,Lamivudine|Hivid,Zalcitabine|Kivexa,Abacavir%20and%20Lumivudine|Retrovir,Zidovudine|Trizivir,Abacavir%20and%20Lamivudine%20and%20Zidovudine|Truvada,Tenofovir%20and%20Emtricitabine|Videx,Didanosine|Viread,Tenofovir|Zerit,Stavudine|Ziagen,Abacavir[/vc_table]
[vc_table vc_table_theme=”simple”]Commercial%20Name,[b]Active%20Drug|Sustiva,Efavirenz|Viramune,Nevirapine|Edurant,Rilpivirine|Intelence,Etravirine[/vc_table]
[vc_table vc_table_theme=”simple”]Commercial%20Name,[b]Active%20Drug|Agenerase,Amprenavir|Aptivus,Tipranavir|Crixivan,Indinavir|Invirase,Saquinavir|Kaletra,Lopinavir%20and%20Ritonavir|Telzir,Fosamprenavir|Norvir,Ritonavir|Prezista,Darunavir|Reyataz,Atazanavir|Viracept,Nelfinavir[/vc_table]
[vc_table vc_table_theme=”simple”]Class,[b]Active%20Drug|Isentress,Raltegravir|,Eviltegravir|,Dolutegravir[/vc_table]


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.