You are here:

Therapeutic Drug Monitoring (TDM)

Published on


Therapeutic Drug Monitoring (TDM)

Important Communication regarding Therapeutic Drug Monitoring (TDM) Unit’s ISO15189:2012 accreditation.

We have been working hard during Covid-19 pandemic to keep the anti-epileptic drugs therapeutic drug monitoring service going.

As you were notified 23 April 2019, we had voluntarily suspended the TDM Unit’s United Kingdom Accreditation Service (UKAS) ISO 15189:2012 accreditation in order to take the necessary time to fully update its Quality Management Systems (QMS). In February 2020, our customer survey returns showed us that although happy with the level and quality of the service, our clients were understandably looking forward to the TDM Unit become again an accredited laboratory. We have been working steadfastly to achieve this and the TDM Unit has recently undergone two remote assessments by UKAS in line with their re-accreditation process.

We are delighted to announce that we have fulfilled our aim and our clients’ friendly recommendation in that the TDM Unit’s ISO 15189:2012 accreditation has now been reinstated and the Unit’s accreditation status is now displayed on UKAS’s website amongst accredited medical laboratories. We are also happy to let you know that all tests we offer are now included in our schedule (including recently added brivaracetam).

We would like to thank you for your continued support in terms of anti-epileptic drug test referrals during the covid-19 pandemic and can now confirm that our turnaround times are back to 3 working days from the receipt of the sample.

Thank you for your cooperation and faith in the TDM during this very challenging time. We look forward to continuing to provide all of your anti-epileptic drug testing needs.

Yours sincerely,
Dr Karin Kipper
Head of Therapeutic Drug Monitoring Unit
Epilepsy Society

Our Therapeutic Drug Monitoring (TDM) Unit will undertake the detailed pharmacokinetic investigation of individual patients with unusual clinical response to drugs during therapy or following overdose. Presently, it is the only AED TDM service in the UK which provides an analytical service for 24 AEDs currently licensed for clinical use and 2 pharmacologically active metabolites.

The Unit provides a specialist AED TDM service for in-patients and out-patients attending the National Hospital for Neurology and Neurosurgery (Queen Square), University College Hospitals NHS Trust and Epilepsy Society. Also, sample referrals are received from many NHS and private hospitals, institutions, forensic laboratories, private pathology laboratories and from veterinary practices throughout the UK. The service provision is cost effective and with rapid turnaround times.

Read our user's guide to therapeutic drug monitoring of antiepileptic drugs.


What is Therapeutic Drug Monitoring (TDM)?

Therapeutic drug monitoring (TDM) is an area of clinical chemistry that specialises in measuring medication levels (concentrations) in patients, usually through blood samples but also through saliva samples. Because anti-epileptic drugs are among the types of drugs that can be easily under dosed or over dosed, they are particularly suitable for monitoring. The measured levels are used by the doctor to adjust each patient’s individual dosage and schedule to each patient’s individual therapeutic requirement. Thus, drug efficacy (the anti-epileptic effect of a drug) is kept to a maximum while the undesirable side effects are kept to a minimum.

Monitoring antiepileptic drugs

There are now 27 anti-epileptic drugs (AEDs) licensed for the management of patients with epilepsy in the UK. We offer a TDM service for 24 of these drugs and 2 pharmacologically active metabolites. During the past 10-20 years therapeutic monitoring of anti-epileptic drugs has served to substantially enhance the management of patients with epilepsy because drug administration (prescriptions) can be individualised.

Our Therapeutic Drug Monitoring Unit (TDM)

We provide a TDM assay service for AEDs and a pharmacokinetic consultation service (looking at how drugs distribute in the blood over time) to help individualise patient drug therapy. We carry out detailed pharmacokinetic investigation of individual patients who have experienced an unusual clinical response to drugs during therapy or following overdose.

We provide a specialist AED analytical service to the National Hospital for Neurology and Neurosurgery, University College Hospitals NHS Trust, and to many hospitals and organisation throughout the UK and from Europe.

How can the service be accessed?

Chalfont Centre switchboard number 01494 601 300
Main Laboratory 01494 601 424
Patient results and enquiries 01494 601 423
Consultant Clinical Scientist/Head of Unit Dr K Kipper 01494 601 423
Transformation Advisor Mr F McQueen 01494 601 355
Consultant Clinical Scientist (part-time)  Dr E. P. Spencer 01494 601 424
Clinical Scientist Mr A. W. James 01494 601 424
Clinical Scientist Mr F. P. Quinlivan 01494 601 424
Quality & Administration Manager Mrs Kate Choinkowska 01494 601 490
Phlebotomy Services Mrs Julie Dick 01494 601 345
Phlebotomy Services Ms Jolanta Krysa 01494 601 345
Medical Director Professor J. W. Sander 01494 601 343

Using the TDM service

The assay service is routinely available Monday to Friday, 9am-5pm. For urgent assay requests, please contact the unit in advance. The unit will report on non urgent assay requests within 3 working days of receiving the sample in the laboratory, excluding weekends or bank holidays.

Sample type

The matrix of choice is serum or plasma, and although they can be used inter-changeably it is preferable to use one or the other. In most clinical settings the measurement of total serum concentrations will suffice and indeed most routine methods for measuring AEDs in sera do not discriminate between the component of drug that is free (unbound) and that that is bound to serum proteins.