TDM in Europe gets a boost from remote microsampling

Kang and Lee define TDM (therapeutic drug monitoring) as a clinical laboratory measurement of a particular drug in a patient’s bloodstream that, with proper medical interpretation and optimized and individualized dosage regimen, enables maintaining the drug’s concentration within a targeted therapeutic range. In Europe, TDM programs are getting a boost from remote specimen collection and microsampling technology.

Adult organ transplant patients at Guy's and St Thomas, an NHS Foundation Trust hospital in the UK, and Rennes University Hospital in France, are using remote specimen collection devices to enable their therapeutic drug monitoring to continue while they remain safe at home. After an organ transplant procedures, patients must typically take drugs such as tacrolimus, to prevent ensure organ function and prevent organ rejection.

Dosing of tacrolimus and creatinine must be monitored closely in patients who have received kidney transplants, for example. Previously, these patients had to travel frequently to the hospital for specimen collection and in-person TDM consultations. Pediatric organ transplant patients at Nottingham Children's Hospital in England also are benefitting from a program that provides remote specimen collection kits for at-home TDM.

Thanks to Mitra^® devices based on volumetric absorptive microsampling (VAMS^®), patients in the UK and Europe can get specimen collection kits from their hospital delivered by mail. They use the kits to self-collect their own specimen samples at home and send them back to their designated lab via regular mail.

The samples are processed and analyzed to determine if the drug levels in each patient's system are optimal. The care team accesses the lab results through a secure digital system, and follows up with patients via phone or a video call to discuss results and any dosing changes. 

A Closer Look at Therapeutic Drugs That Can Be Monitored Remotely 

Not every drug needs to be monitored, and certain criteria need to be met for TDM technology to be a sound practice. Drugs that can and should be monitored, include:

• Quality drug assays — To even consider TDM for a specific drug, accurate, precise, sensitive, and specific drug assay procedures must be in place to account for any clinically relevant information, such as dosage regimen, time of sampling, and patient condition.
  
  
• Drugs used for treatment of life-threatening conditions — TDM is critical where the lack of therapeutic effect is dangerous for the patient (i.e., bisoprolol, used for treatment of heart failure), the drug itself has a low therapeutic index and is considered unsafe (i.e., paracetamol), or both (i.e., theophylline, used for treatment of respiratory diseases such as chronic obstructive pulmonary disease).
  
  
• Drugs that exhibit high intra-specific variability — TDM can track high variability in terms of pharmacokinetics (poor relationship between applied dose and the amount of free drug exerting pharmacological effect) and low intra-specific variability in terms of pharmacodynamics (good relationship between the serum drug concentration (SDC) and pharmacological effect).

How Technological Advancements Help Patients in TDM Programs

Just a quick look at the TDM criteria reveals that the sensitive populations that benefit the most from TDM – newborns, the elderly, chronically ill, or terminally ill patients, individuals with disabling conditions – are likely to be the most strained by traditional TDM requirements, especially the frequent clinic visits and invasive blood draws that include sampling of large volumes of blood.

These are the very patients who can benefit most from remote technologies and tools that allow them to use minimally invasive self-sampling while safe at home to avoid unnecessary travel and exposure to contagions.

Microsampling Advances Pharmacokinetics While Keeping Patients Safe

Technological advancements in all medical fields, alternative sampling matrices, such as dried microsamples, allow for many applications of remote TDM, providing the most vulnerable patients with a host of benefits, including:

• Home-based TDM removes the strain of frequent visits to a medical facility
• Robust, non-invasive procedures are suitable for self-sampling while providing relevant clinical data from capillary blood sampling
• Less invasive, convenient, straightforward sampling promotes patient compliance, further aiding in therapy optimization and individualization

Off-site TDM involving remote sampling also facilitates pharmacokinetic studies in critical patient populations for a range of drugs that currently lack this data. Remote specimen collection and microsampling can accelerate this effort. With a better understanding of a drug’s pharmacokinetics in particular populations, along with procedures for cytochrome P450 phenotyping, a better understanding of dose-effect relationship will reduce the need for TDM, leading to increased patient care with less strain on the patients themselves.