What Are the Different Types of PK Sample?

Pharmacokinetic (PK) samples offer extensive insight into how substances are processed by living organisms. Samples are collected and processed under a branch of pharmacology known as pharmacokinetics, a term derived from the Greek words “pharmakon” meaning "drug" and “kinetikos” meaning “motion”. From pharmaceutical drugs to pesticides, PK samples are used to unlock data across a diverse range of industries. Read on to find out more about the different types of PK samples and how they’re used.  

The four pillars of pharmacokinetics

PK samples track how a substance travels through a living organism, with scientists focusing on four different phases - absorption, distribution, metabolism and excretion. Abbreviated to ADME, these four phases chart the entire journey of the substance, from initial absorption to final excretion.

The field is especially valuable to the pharmaceuticals industry as it offers a complete map of how a drug travels through the body. Data is used to determine how effective a drug is and if its safe to market on a commercial scale. As well as drug development, pharmacokinetics can be applied in a clinical context to manage therapeutic drugs administered to an individual patient. Data can be used to track the performance of a drug, as well as optimise dosages.

The role of blood, urine, saliva and plasma

Blood is the most common type of pharmacokinetic sample as it offers an accurate and reliable measurement of drug concentrations. While measuring concentrations directly at the site of action is preferable, this isn’t always possible as receptor sites are usually inaccessible. For example, the drug digoxin used to treat heart failure interacts with receptor sites within muscular heart layers known as the myocardium. Samples cannot be extracted from these tissues, making blood a useful alternative.

As well as blood, PK samples can be collected from other bodily fluids such as urine, saliva and plasma. Each type of PK sample has its own unique benefits, with methods selected based on the type of drug being analysed. Urinary PK samples are an effective way to determine how much of a drug is absorbed by the body and how much is eliminated through the kidneys. Plasma PK samples can be useful when blood concentrations of a drug are low, and a more sensitive approach is required. One of the main benefits of saliva PK samples is the easy and non-invasive nature, making them ideal for certain biomonitoring applications.

PK samples and biobanks

As well as being used to diagnose and treat individual patients, PK samples are invaluable resources for biobanks. They’re fundamental to medical research though despite their value, PK samples can be incredibly hard to acquire. Robert Hewitt, founder of Welsh-based company Biosample Hub explores the issue further and puts forward a clever solution in ‘The challenges of biosample access and what needs to change.’